Intern Emerg Med DOI 10.1007/s11739-015-1272-y
IM - REVIEW
The influence of early-life conditions on cardiovascular disease later in life among ethnic minority populations: a systematic review Rimke Bijker1 • Charles Agyemang1
Received: 1 May 2015 / Accepted: 10 June 2015 Ó SIMI 2015
Abstract Ethnic minority groups are disproportionately affected by cardiovascular diseases (CVDs). The reasons for the high prevalence of CVD in ethnic minority groups are not fully understood. Recently, the importance of earlylife developmental factors and their impact on CVDs in adulthood is increasingly being recognised, but little is known about this among ethnic minority groups. Therefore, the current paper aimed to fill this knowledge gap by reviewing the available literature to assess the influence of early-life conditions on CVDs and its risk factors in ethnic minority populations residing in Western countries. A systematic search was performed in PubMed and EMBASE between 1989 and 2014. In total, 1418 studies were identified of which 19 met the inclusion criteria. Six studies investigated the relationship between early-life anthropometrics and CVD risk factors of which all except one found significant associations between the assessed anthropometric measures and CVD risk factors. Seven studies evaluated the influence of childhood socio-economic status (SES) on CVD and risk factors of which five found significant associations between childhood SES measures and CVD risk factors. Five studies investigated the relationship between other early-life conditions including early-life nutrition, physical development, and childhood psychosocial conditions, and CVD risk factors. Four of these studies found significant associations between the assessed childhood conditions and CVD risk factors. This review reinforces the importance of early-life conditions on adult
& Charles Agyemang [email protected] 1
Department of Public Health, Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands
CVD in ethnic minority groups. Improvement of early-life conditions among ethnic minority groups may contribute to reducing CVD risk in these populations. Keywords Early-life condition Cardiovascular disease Ethnic minorities Ethnic health
Introduction Findings from the Global Burden of Disease study 2010 indicate that worldwide, more than half of all Disability adjusted life years (DALYs) are due to cardiovascular diseases (CVDs), such as ischemic heart disease and stroke [1]. A relatively high proportion of this disease burden in high-income countries is attributable to intermediate risk factors, such as high blood pressure and obesity [2]. Ethnic minority groups have been particularly affected by CVDs and its intermediate risk factors compared with the European host populations for reasons that are not well understood [3–6]. Hence, there is a need for knowledge on how CVD develops, in particular, in ethnic minority populations. Recently, the importance of early-life developmental factors and their influence on CVDs in adulthood is increasingly being recognised [7–9]. A wide variety of studies have been conducted to evaluate the influence of early-life conditions on CVDs in adulthood, and various literature reviews have summarised the findings in both Western and non-Western countries [10–13]. However, none of these reviews focused explicitly on ethnic minorities. The current paper aimed to fill this gap by reviewing the available literature to assess the influence of early-life conditions on CVDs, principally heart disease and stroke and its risk factors (hypertension, diabetes,
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obesity/adiposity, dyslipidaemia and diabetes) in ethnic minority populations residing in Western countries (i.e. the USA, Canada, Western Europe, Australia and New Zealand). Early life in this paper is defined as the time frame from birth up to approximately 16 years.
Methods A systematic search was performed with scientific literature databases (PubMed and EMBASE) using combinations of the key words ‘‘cardiovascular disease’’, ‘‘early life’’, ‘‘later in life’’, ‘‘ethnic minority population’’ and alternatives of these words. A specific search syntax was developed in collaboration with an experienced librarian (see Table 2 in ‘‘Appendix’’). The search was restricted to papers published between 1989 and 2014, since the theory of early-life conditions as determinants of late-life health originates from a study conducted in 1989, by Barker and colleagues [14]. A manual search was conducted to identify further relevant studies. The search results were screened by title and abstract for potential eligibility. Studies published in the English language were eligible for inclusion if they evaluated the relationship between early-life conditions and CVDs later in life in
ethnic minority populations and had a longitudinal or cross-sectional design. Studies were excluded if they were conducted in non-Western settings; had a main outcome other than CVDs or its intermediate risk factors; or did not focus on the association between early-life conditions and outcome later in life. Furthermore, studies were excluded if they combined ethnic minority populations with the host majority populations. Full texts were obtained and screened if articles met the inclusion criteria. If articles were excluded during the full-text screening, reasons for exclusion were documented (Fig. 1). Data extraction and synthesis Several steps were followed to extract the data. Firstly, a data extraction form was developed in Microsoft Excel to record relevant study details. Data were extracted on study design, setting, population, early-life conditions, outcomes, other variables included in the analysis and main findings of the study. Secondly, studies were categorised according to the early-life conditions they investigated. The study characteristics and the results were summarised by early-life condition and grouped according to health outcome if applicable. Furthermore, if studies compared ethnic minority populations with a host
Identification
Fig. 1 Study selection Records identified through database searching (n= 1416)
Additional records identified through other sources (n = 2)
Included
Eligibility
Screening
Records after duplicates removed (n = 1293)
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Records screened (n = 1293)
Records excluded (n = 1255)
Full-text articles assessed for eligibility (n = 38)
Full-text articles excluded, with reasons
Studies included in qualitative synthesis (n = 19)
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Results not stratified by ethnicity (n =8) No CVD (risk) specified (n=3) No cohort/cross-sectional study (n=1) No focus association early life and CVD (n=7)
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population group, differences and similarities were described whenever feasible.
use or exercise) [19, 20, 24–26, 32]; and six for family history of CVD [19, 20, 22, 26, 32, 35]. One study did not adjust for any form of confounding [34].
Note on ethnicity Early-life anthropometrics and CVDs There is no consensus on appropriate terms for the scientific study of health by ethnicity, and published guidelines are yet to be widely adopted. Ethnicity usually refers to a group that shares a range of cultural characteristics, such as ancestry, religion, language and diet [15]. However, ethnicity and the biological term race are often used interchangeably and inappropriately [16]. In Western countries, the term ethnic minority group is commonly used to indicate non-White populations of non-European descent [15]. Yet, methods by which participants are categorised into a specific ethnic minority group are often unclear [16]. This review follows present general conventions in terminology of ethnic groups. Several terms, such as ‘‘blacks’’ and ‘‘black Americans’’, were used by authors to refer to African origin populations in the USA studies. For simplicity, we used the term ‘‘African Americans’’ to refer to African origin populations in the USA.
Results In total, 1418 studies were identified from the systematic and manual searches. Of these, 38 full-text articles were assessed for eligibility, of which 19 studies were excluded because they did not meet the selection criteria (Fig. 1). Of the remaining 19 studies (Table 1), 17 were conducted in the USA and two in Australia [17, 18]. Eight studies had a cross-sectional design [17, 19–25], whereas 11 studies were of longitudinal nature [18, 26–35]. Six studies were based on African Americans [19, 21, 24, 25, 31, 34], three were based on Pima Indians [22, 27, 28], one on Japanese Americans [20] and two on Australian aboriginals [17, 18]. In the remaining seven studies, the population entailed both African-American and White participants [26, 29, 30, 32, 33, 35], or Mexican-American and non-Hispanic-White participants [23], allowing for direct comparisons between the groups. Study sample sizes ranged from 134 to 3978 participants in the ethnic minority populations and from 128 to 17,642 participants in the White populations. Several exposures were assessed in the included studies, such as early-life anthropometrics in seven studies [17, 18, 23, 27, 28, 34, 35], childhood SES in seven studies [21, 24, 29– 33] and other childhood influences in five studies [19, 20, 22, 25, 26]. The studies differed in inclusion of established risk factors for CVDs. Eight studies adjusted their analyses for adult socio-economic status (SES) [19, 21, 24, 26, 31– 33, 35]; seven for presence of risk factors in adulthood [17, 19, 20, 24, 26, 32, 33]; six for lifestyle (smoking, alcohol
Seven studies investigated the relationship between earlylife anthropometrics and CVD risk factors [17, 18, 23, 27, 28, 34, 35]. All studies found significant associations between the assessed anthropometric measures and outcomes, except for one among African Americans [34]. However, the findings varied by ethnicity and gender. For example, one study compared Mexican-American and non-Hispanic-White men and women regarding the influence of birthweight on subscapular-to-triceps-skinfold ratio, blood pressure, fasting insulin, fasting glucose and lipids at age 25–64 [23]. Among Mexican-American women, low birthweight was related to most risk factors, whereas no such relations were found among Mexican-American men. Similarly, no relationships were found among White-American men and women except for a significant inverse relationship between birthweight and triglycerides in men. On the contrary, one study among Australian Aboriginals found a positive association between birthweight and fasting glucose levels [18]. Furthermore, in another study that assessed the effect of obesity on diabetes among African Americans and White Americans, African Americans who were obese in early adolescence had over a twofold risk of developing diabetes compared with those without obesity, whereas no significant associations were found in White Americans. [35]. Childhood SES Seven studies assessed the influence of childhood SES on CVDs (heart failure [33] and stroke [29]) and risk factors (metabolic syndrome [31], obesity [30], hypertension [21, 24] and inflammatory risk markers [32]) later in life. Childhood SES was based on a variety of measures including parental education [21, 29, 30, 32, 33], parental occupation [24, 29, 31–33], home ownership of parents [33], SES of the neighbourhood that a child was exposed to [32], number of rooms in the childhood home and access to household assets [21], family structure characteristics [30] and adult height as a marker of childhood SES [29]. Three studies combined variables into a composite measure to specify childhood SES [21, 29, 32], and three studies created variables to asses SES over the course of childhood to adulthood [21, 24, 32]. Of the seven studies, five found associations between at least some of the childhood SES measures and the CVD and risk factor [21, 24, 29, 30, 32], whereas two studies did not find any significant associations [31, 33]. Interestingly, one of these two studies used a sole indicator of childhood SES (i.e. parental occupation) and assessed its association with
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Setting
USA
Australia
Australia
USA
USA
Falkner et al. [34]
Singh and Hoy [17]
Sayers et al. [18]
Valdez et al. [23]
De Courten et al. [28]
Early-life anthropometrics
References
Longitudinal
Cross-sectional, San Antonio Heart Study
Longitudinal, Aboriginal Birth Cohort Study
Cross-sectional
Longitudinal, PCP Philadelphia
Design, part of larger study
188 Pima Indians, age 5–9 years, followed up at age 18–24 years
413 Mexican Americans and 128 non-Hispanic White Americans, age 25–64 years
134 Aboriginals, followed from birth up to mean age 18.3
767 Australian Aboriginals, age 7–43 years
137 African Americans, followed from birth up to age 28 years
Population, age, follow-up period (if applicable)
Table 1 Description of studies included in the review
Childhood mean blood pressure, relative weight (age standardised BMI)
Birth weight
Birth weight
Birth weight (ponderal index)
Birth weight and birth adiposity (ponderal index)
Exposure
Hypertension in adulthood (additional analysis)
Mean blood pressure in adulthood
Metabolic, anthropometric, heamodynamic characteristics
Fasting glucose and insulin levels
Current blood pressure
Adult blood pressure
Outcome
No significant association was found between childhood relative weight and hypertension in adulthood.
Adjusted for age.
Additional analysis performed on 67 men in population (no data available for women).
Relative weight was associated with mean blood pressure (p \ 0.05, no effect size provided).
Adjusted for age.
In non-Hispanic White-American men, participants in the lowest birth weight tertile had higher plasma triglycerides (p, 0.025).
In Mexican-American men, no significant associations were found between birth weight and the assessed characteristics.
In non-Hispanic White-American women, no significant associations were found between birth weight and the assessed characteristics.
In Mexican-American women, participants in the lowest birth weight tertile had higher subscapular-to-triceps-skinfold ratios (p, 0025); SBP (p, 0.020); DBP (p, 0.033); fasting insulin (p, 0.001); and fasting glucose (p, 0.040).
Adjusted for age, stratified by sex and categorised by birth weight.
No significant association was found between birth weight and insulin levels.
1 kg increase of birth weight was associated with 7 % rise of fasting glucose level (p, 0.002).
1 kg increase of birth weight was associated with 2.9 mmHg decrease in systolic BP (95 % CI 0.3–5.5 mmHg). Adjusted for age, sex and gestational age.
Adjusted for age, sex and current weight.
No significant correlation was found between birth weight and adult BP. No significant correlation was found between birth ponderal index and adult BP.
Not adjusted for other variables.
Main findings
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USA
Franks et al. [27]
USA
USA
USA
Lucove et al. [31]
Roberts et al. [33]
Robinson et al. [30]
Childhood SES
The et al. [35]
Setting
References
Table 1 continued
Longitudinal, Add Health
Longitudinal, ARIC
Longitudinal, Pitt County Study
Longitudinal, Add Health
Longitudinal
Design, part of larger study
2096 African American and 5651 White nonimmigrant American young adults, age 11–19, followed up for 7 years
8519 White Americans, mean age 53.9 years, median follow-up period 16.2 years
2503 African Americans, mean age 52.8 years, median follow-up period 16.0 years
1407 African Americans, age 25–50, followed up for 13 years
2096 African Americans and 6218 White Americans, age 11-21 followed up until age 24–34
1604 Pima Indians, age 5–19 years, median follow-up period 5.5 years
Population, age, follow-up period (if applicable)
Childhood sociodemographic characteristics (parental education, family structure, female caregiver’s age at child’s birth, number of minors in household, number of siblings, birth order)
Early-life SEP (parental education, occupation and home ownership of parents/caregivers)
Parental occupation
Adolescent obesity onset (before or after age 16 years)
Waist circumference
Exposure
Obesity (gender disparity)
Heart failure
Metabolic syndrome
Prevalent diabetes
Incident diabetes
Outcome
In White Americans, there was no significant gender disparity.
In African Americans, parental education was strongly associated with the gender disparity in obesity. African-American women from loweducation families were at the greatest risk of obesity, whereas African-American men from low-education families were at the lowest risk for obesity.
Adjusted for age.
No association was found between early-life SEP and heart failure in neither African Americans nor White Americans.
Adjusted for age, sex, study centre, young adulthood SEP, mid-to-older adulthood SEP and heart failure risk factors.
No significant association was found between parental occupation and metabolic syndrome.
Adjusted for age, sex and adult SES.
In White Americans, no significant association was found for adolescent obesity onset and prevalent obesity.
In African Americans, adolescent obesity (onset \ 16 years) was associated with increased prevalence of diabetes (OR 2.25; 95 % CI 1.01–4.98) as compared to adulthood obesity onset.
Adjusted for age, education, sex, parental history of diabetes.
1 SD difference in waist circumference (HRR 2.2; CI 1.8–2.7) and BMI (HRR 2.2; CI 1.6–2.2) at young age were strong predictor traits of incident diabetes.
All predictor traits were associated with incident diabetes.
Adjusted for age, sex and Pima Indian heritage.
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Setting
USA
USA
USA
References
Glymour et al. [29]
James et al. [24]
Subramanyam et al. [21]
Table 1 continued
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Cross-sectional, Jackson Heart Study
Cross-sectional, Pitt County Study
Longitudinal, Health and Retirement Study
Design, part of larger study
3978 African Americans, age 21–95 years
379 African-American men, age 25–50, followed up for 13 years
3019 African Americans and 17,642 White Americans, age 50? , mean follow-up period 9.3 and 9.5 years, respectively
Population, age, follow-up period (if applicable)
Childhood SES (based on parental education, number of rooms in the home and access during childhood to households assets such as indoor plumbing, refrigerator and tv) and cumulative SES
Life-course SEP (childhood/adult occupation)
Childhood SEP (parental occupation)
Parental SES (mothers education, fathers education and fathers occupation), adult height and retrospective health
Exposure
Hypertension
Hypertension
First stroke onset
Outcome
In women, participants categorised in the middle childhood SES tertile (PR 1.09; 95 % CI 1.00–1.20) and in the middle and lowest cumulative SES tertile (PR 1.09; 95 % CI 1.00–1.20 and PR 1.16; 95 % CI 1.06–1.27, respectively) had a higher prevalence of hypertension than women in the highest SES tertiles.
In men, no significant association was found between childhood SES or cumulative SES and hypertension.
Adjusted for age and adult SES; stratified by sex.
High/low SEP (OR 5.87; 95 % CI 1.25–27.49) and low/low life-course SEP (OR 7.27; 95 % CI 1.91–27.51) were associated with hypertension as compared to high/high life-course SEP.
No significant associations were found between childhood SEP and hypertension.
In White American, father’s education less than 8 years (HR 1.24; 95 % CI 1.03–1.48) as compared to longer than 8 years and fair or poor childhood health as compared to good, very good or excellent health (HR 1.31; 95 % CI 1.09–1.58) and the composite measure of low parental SES (HR 1.27; 95 % CI 1.09–1.48) were associated with first stroke onset. Adjusted for age, BMI, waist-hip ratio, adult SEP, marital status, alcohol, smoking, strenuous exercise, perceived stress, John Henryism, instrumental support, emotional support.
In African Americans, no significant associations were found between any of the exposures and first stroke onset.
Adjusted for age, sex, Southern birth state and Hispanic ethnicity.
Main findings
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USA
Pollitt et al. [32]
USA
USA
Smits et al. [20]
Pettitt et al. [22]
Other early-life influences
Setting
References
Table 1 continued
Cross-sectional, infant feeding data provided in earlier stage
Cross-sectional, JapaneseAmerican Community Diabetes Study
Longitudinal, ARIC? LCSES
Design, part of larger study
720 Pima Indians, age 10–39 years
464 2nd/3rd generation Japanese Americans, mean age men with diabetes 60.9; men without diabetes 49.3; women with diabetes 62.2; and women without diabetes 50.4 years
2761 African Americans and 9081 White Americans, age 45–64 years, retrospectively asked about early life
Population, age, follow-up period (if applicable)
Breastfeeding
Total, upper and fore arm length; total and lower leg length; and height (as markers of early-life environment and development)
Cumulative life course SES based on number of exposures to social class (in childhood, young adulthood and mature adulthood), to level of education (of participant and participant’s father) and to contextual/ neighbourhood-level SES (in childhood, and young and mature adulthood)
Exposure
Type 2 diabetes
Type 2 diabetes
Levels of inflammatory risk markers (fibrinogen, white blood cell count, CRP, van Willebrand factor)
Outcome
Exclusive breastfeeding was associated with less diabetes compared to exclusive bottle feeding (OR 0.41; 95 % CI 0.18–0.93).
Adjusted for sex, age, birth weight, parental diabetes, birth year.
No significant associations were found between fore arm length; total and lower leg length; and height, and type 2 diabetes.
1 SD increase in total arm length (OR 0.49; 95 % CI 0.29–0.84) and upper arm length (OR 0.56; 95 % CI 0.36–0.87) were inversely related to type 2 diabetes.
Adjusted for age, sex, weight, height (only in models regarding arm length) intra-abdominal fat area, family history of diabetes and smoking status.
In White-American participants, higher cumulative exposure to lowest education group and worker class group were associated with fibrinogen (p for trend, 0.0054 and 0.02, respectively) and with white blood cell count (p for trend, 0.0014 and 0.04, respectively).
In African-American participants, the only association was between higher cumulative exposure to worker class group and CRP (p for trend, 0.027).
Adjusted for age, sex, study centre, adult SES measures, HDL-C, LDL-Cl, BMI, hypertension and hypertension medication, family history of CVD, diabetes status, alcohol intake, smoking status and cigarette-years smoked.
Main findings
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USA
USA
USA
Dreyfus et al. [26]
Spann et al. [25]
Barrington et al. [19]
Cross-sectional, Howard University Family Study
Cross-sectional
Longitudinal, ARIC
Design, part of larger study
515 African-American men, mean age 48 years
452 African Americans, age [ 18 years
2505 African-American and 5986 White-American women, mean age 53,3 and 54.0 years, respectively, followed up for 9 years
Population, age, follow-up period (if applicable)
Socio-familiar conditions (years lived with both parents)
Childhood trauma
Age at menarche
Exposure
Hypertension
HDL-C/LDL-C ratios
Type 2 diabetes
Outcome
Living with both parents (1–12 years) was protective for hypertension later in life (OR 0.54; 95 % CI 0.30–0.99) as compared to not having lived with both parents.
Adjusted for age, education, marital status, employment, smoking, sodium/potassium ratio, HDL-C, obesity, diabetes mellitus and family history of hypertension.
In women, no significant associations were found between childhood trauma and HDL-C/LDL-C ratio.
In men, higher childhood trauma levels were inversely associated with HDL-C/LDL-C ratio (b, -0.179; p, 0.038).
Adjusted for age, alcohol use, smoking and adult trauma.
In White-American women, early age at menarche (8–11) was associated with type 2 diabetes (OR 1.41; 95 % CI 1.05–1.89) as compared to menarche at age 13 years.
In African-American women, no significant association was found between age at menarche and type 2 diabetes.
Adjusted for age, study centre, education level, BMI (baseline and at age 25 years), baseline height and waist circumference, smoking status, use of oral contraceptives and family history of diabetes.
Main findings
PCP Perinatal Collaborative Project, Add Health National Longitudinal Study of Adolescent Health, ARIC Atherosclerosis Risk in Communities Study, LC-SES Life Course Socioeconomic Status, Social Context and Cardiovascular Disease Study, BP blood pressure, SBP systolic blood pressure, DBP diastolic blood pressure, SEP socio-economic position, SES socio-economic status, CRP C-reactive protein, HDL-C high-density lipoprotein cholesterol, LDL-C low-density lipoprotein cholesterol, BMI body mass index, CVD cardiovascular disease, A1C test to assess diabetes, mmHG millimetre of mercury, OR odds ratio, p probability, SD standard deviation, HRR hazard rate ratio, CI confidence interval, PR prevalence ratio, HR hazard ratio
Setting
References
Table 1 continued
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metabolic syndrome in an African-American population [31], whilst the other used several separate measures (i.e. parental education, occupation and home ownership of parents) as well as a composite measure to investigate the influence of childhood SES on heart failure in African Americans and White Americans [33]. Furthermore, the association of childhood SES measures with CVDs and risk factors varied by ethnicity and gender. Two studies found distinct differences across ethnic groups in evaluating the effect of childhood SES on stroke and obesity [29, 30]. For instance, differences were found between African Americans and White Americans that were followed up to investigate the gender disparity in obesity [30]. Among African Americans growing up in low-education families, young women were at greatest risk, whereas young men were at lowest risk of developing obesity. Among White Americans, however, no notable difference was found in obesity across gender. Another study assessed the influence of childhood SES (mother’s education, father’s education, father’s occupation, childhood health and height) on stroke risk [29]. Among African Americans, none of the associations yielded significant results when childhood indicators were included in one model, whereas among White Americans, relatively weak associations were found for father’s education less than 8 years and fair or poor childhood health and stroke risk. Likewise, after creating a composite measure for parental SES, low parental SES was associated with stroke risk in White Americans, but not in African Americans. Shorter stature was associated with stroke risk in both groups. The remaining three studies evaluated the influence of life-course SES on hypertension or inflammatory risk markers [21, 24, 32]. Among African-American men, childhood SES alone, measured as parental occupation, did not have an effect on hypertension, whereas life-course SES did (parental and adult occupation) [24]. Participants who maintained a low SES throughout their lives, and those who degraded from a high to a low SES, had a strongly increased risk of hypertension as compared to participants who maintained a high SES. In a comparable study on AfricanAmerican men and women, cumulative SES was created by combining a composite measure of childhood SES and adult SES [21]. No significant effects of childhood or cumulative SES were found in men, whereas in women, those categorised in the middle childhood SES tertile and in the middle and lowest cumulative SES tertile had a slightly higher prevalence of hypertension than women in the highest SES tertiles. In addition, measures of life-course SES (i.e. number of exposures to social class and neighbourhood-level SES throughout the course of life and education of participant and participant’s father) and inflammatory risk markers (i.e. fibrinogen, C-reactive protein, white blood cell count and van Willebrand factor) were evaluated in African Americans and White Americans [32].
Among African Americans, a weak association was found for those with high cumulative exposure to working class group and C-reactive protein. For White Americans on the other hand, high cumulative exposure to lowest education group and working class group were associated with fibrinogen and white blood cell count. Other early-life influences Five studies were identified that investigated the influence of other early-life conditions on CVD and risk factors later in life, of which all except one found significant effects of their exposure variables among ethnic minorities [19, 20, 22, 26]. Three of these studies assessed the influence of physical development and nutrition on diabetes [20, 22, 25]. For instance, arm and leg length were investigated as proxy measures for early-life nutrition in Japanese Americans [20]. After adjusting for relevant confounders, total arm length and upper arm length were inversely associated with having diabetes, whereas other measures of limb length were not. In addition, early-life nutrition was assessed as having been breast- or bottle-fed in Pima Indians [22]. Findings indicated that breastfeeding is strongly associated with a decreased risk of developing diabetes independently of birth weight and parental diabetes. Furthermore, the effect of age at menarche was studied in African-American and WhiteAmerican women [26]. The findings reveal that having diabetes was independently associated with early age of menarche (8–11 years as compared to 13 years) in WhiteAmerican women, but not in African-American women. The remaining studies investigated the relationship between psychosocial conditions in childhood and CVD later in life. For instance, one study assessing the association between childhood trauma and cholesterol levels found that among men, but not among women, higher levels of childhood trauma were associated with reduced high-density lipoprotein/low-density lipoprotein ratios [25]. Another study examined childhood living situation in relation to hypertension in African-American men [19]. The study found that living with both parents for 1–12 years (as opposed to living with only one parent) is protective of hypertension later in life independent of confounding factors.
Discussion Key findings This literature review assessed early-life conditions related to late-life CVD and risk factors in ethnic minority populations residing in Western settings. The findings suggest that for these populations, being born with high birthweight and receiving breastfeeding are protective of CVDs and its
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risk factors, whereas childhood overweight has an adverse effect on CVDs later in life. Furthermore, low childhood SES, especially when accompanied by low SES in adulthood, also has an adverse effect on CVDs, although the findings on this topic were somewhat inconsistent and tended to vary by ethnicity and gender. Discussion of the key findings Numerous reviews have found evidence for the contributions of early-life influence on CVDs and risk factors later in life. For instance, low childhood SES has been linked to conditions such as elevated blood pressure, diabetes, heart disease, and CVD mortality in low- and middle-income countries as well as in high-income countries [10, 11, 36]. It has been acknowledged though, that the effect of childhood SES on adult health appears to be greatly mediated by adult SES. The findings of our review, however, suggest an important role of SES throughout the course of life on CVDs and risk factors among ethnic minorities. Of note, findings from the Health and Retirement study, in which data of different ethnic groups were pooled using a novel modelling approach, indicate that the effect of childhood SES on CVDs and risk factors are independent of adult SES [37]. These findings suggest that although adult SES may be an important determinant of adult health, the influence of social and economic conditions in early life should not be underestimated in either ethnic minority populations or the population as a whole. In line with reviews that did not distinguish findings by ethnicity, the findings of this review suggest relationships between early-life anthropometrics and CVDs and risk factors [10, 11, 13, 38], although the findings were somewhat inconsistent and tended to differ by ethnicity and gender. The explanations for the variations across ethnic groups and gender are unclear but may relate to differences in lifestyle. For instance, according to the US health statistics for adults, smoking behaviour, alcohol use and physical activity patterns differ between men and women and between ethnic groups [39]. Thus, contrasting findings in the early-life determinants of CVDs might be attributable to confounding of such lifestyle factors later in life, which were not assessed in all studies. With regard to nutrition in infancy, a large body of evidence has been found supporting the protective effects of breastfeeding [11, 38, 40]. This is consistent with the findings among Pima Indians of the one study that this review identified on the topic [22]. Interestingly, a study that compared data of large birth cohorts from five lowand middle-income countries did not find an association between breastfeeding and hypertension or diabetes [41]. As speculated by the authors of this study, contrasting findings may be explained by different categorisation of
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breastfeeding patterns and the definition of complementary foods. These findings suggest the need for standardisation of data collection methods on early-life conditions to assist the comparability of data across studies. Ethnic minority populations are at increased risk for CVDs, yet statistical models are not commonly stratified by ethnicity to further investigate health disparities [42]. Overall, this review found that the effect of early-life conditions on CVDs in specifically ethnic minority populations was evaluated in a modest number of articles. Almost all of these studies were conducted in the USA. Remarkably, none of the identified studies focused on ethnic minority populations residing in Europe, even though an increasing part of the European population is of non-European descent and ethnic health disparities are greatly apparent [43]. Furthermore, a multitude of studies have indicated relationships between other early-life conditions and CVDs. Some examples are the protective effects of low sodium and protein intake [11, 12, 44] and the harmful effects of parental smoking [45]. The current review was not able to identify any studies that focused on these early-life conditions in ethnic minority populations. The dearth of studies on these topics underscores the need for more studies on early-life conditions and their impact on health outcomes among ethnic minority populations in Europe. Although it is difficult to unravel the complexity of the relationships between early-life conditions and CVDs and their interconnectedness with adult risk factors, recommendations can be drawn from our current findings. Foremost, interventions to reduce health inequalities should pay attention to early-life conditions. The relevance of this is emphasised by evidence showing ‘tracking’ of CVD risk factors. For example, metabolic risk factors such as obesity, insulin resistance, hypertension, and dyslipidaemia tend to cluster from childhood to adulthood [46]. In addition, variability of childhood blood pressure has been associated with hypertension in both African Americans and White Americans [47]. These findings suggest that once unfavourable health outcomes are established, they tend to persist into adulthood and increase future risk of CVDs. Thus, it is crucial to tackle intermediate risk factors as early as possible. In order to adequately address the harmful influence of adverse childhood conditions, further research is warranted into these issues in ethnic minority populations.
Limitations Some limitations should be noted regarding the definitions of early-life conditions and CVDs. Firstly, in most studies, information on early-life conditions was recorded retrospectively by means of self-report [19, 21, 24–26, 29, 31– 33], which are subjected to recall bias. Furthermore, some of
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the studies had small sample sizes. It is possible that these studies were not sufficiently powered to detect significant associations between some of the early-life conditions and CVDs. Secondly, diverse measures were used to assess early-life conditions. For example, childhood SES was measured using a variety of indicators, such as parental education, father’s occupation, and number of rooms in a household. The absence of one congruent measure to assess early-life conditions makes it challenging to compare findings across studies and draw well-founded conclusions. Likewise, the procedures through which outcomes were assessed varied between studies. For instance, the reviewed studies measured blood pressure utilising sphygmomanometers [21, 24, 28, 34] or oscillometric devices [17, 19]. These two methods of measurement are known to obtain different blood pressure results [48, 49]. Hence, it is difficult to compare findings between studies. Another important limitation concerns the use of terms relating to ethnic groups. It should be acknowledged that, although commonly used, some of these terms are broad and unspecific, relating to a heterogeneous group of individuals. For instance, the term African American often refers to people whose ancestors have been living in the USA for multiple centuries as well as more recent immigrants from Africa and the Caribbean [50]. Similarly, the White population can be divided into subgroups with regard to their customs and living style, with some subgroups being more prone to disease than others [15]. As such, using unspecific ethnic labels for heterogeneous population groups might
result in attenuating or abolishing effects that would have been apparent when stratifying by population group [51].
Conclusion In conclusion, this review has assembled the current knowledge available on the influence of early-life conditions on CVD and risk factors in ethnic minority populations. The findings suggest that conditions in young life are indeed important determinants of future cardiovascular health in ethnic minority groups, even though results vary by ethnicity and gender. Undoubtedly, knowledge in this area needs to be extended to reach firmer conclusions about the contribution of early-life conditions to the ethnic health inequalities. In turn, interventions to thwart CVDs early in life need to be tailored to the target populations. Conflict of interest Authors declare they have no conflict of interest. Statement of human and animal rights This article does not contain any studies with animals performed by any of the authors. Informed consent
None.
Appendix See Table 2.
Table 2 Search Strategies Search strategy in PubMed (Dec 10, 2014) 1.
‘‘Adult’’[Mesh] OR ‘‘later in life’’[tiab] OR late*life[tiab]
2.
child*[tw] OR schoolchild*[tw] OR infan*[tw] OR pediatri*[tw] OR paediatr*[tw] OR neonat*[tw] OR boy[tw] OR boys[tw] OR boyhood[tw] OR girl[tw] OR girls[tw] OR girlhood[tw] OR baby[tw] OR babies[tw] OR toddler*[tw] OR newborn*[tw] OR postneonat*[tw] OR postnat*[tw] OR preschool*[tw] OR ‘‘Early life’’[tiab]
3.
‘‘Transients and Migrants’’[Mesh] OR ‘‘Emigrants and Immigrants’’[Mesh] OR ‘‘Ethnic Groups’’[Mesh]
4.
immigrant*[tiab] OR migrant*[tiab] OR ethnic*[tiab] OR minorit*[tiab] NOT medline[sb]
5.
3 OR 4
6.
(‘‘Chronic Disease’’[Mesh] OR Chronic Disease*[tiab] OR Chronic Illness*[tiab] OR ‘‘Chronically Ill’’[tiab] OR non communicable disease*[tiab] OR NCD*[tiab] OR ‘‘Cerebrovascular Disorders’’[Mesh] OR ‘‘Vascular Diseases’’[Mesh] OR ‘‘Heart Diseases’’[Mesh] OR ‘‘Diabetes Mellitus, Type 2’’[Mesh] OR ‘‘Renal Insufficiency, Chronic’’[Mesh] OR ‘‘Kidney Failure, Chronic’’[Mesh]
7.
‘‘Ischemi*’’[tiab] OR ‘‘Stroke’’[tiab] OR ‘‘Hypertension’’[tiab] OR ‘‘Infarct*’’[tiab] OR ‘‘Diabet*’’[tiab]) OR ‘‘kidney’’[tiab] ‘‘renal’’[tiab] NOT medline[sb]
8.
6 OR 7
9.
1 AND 2 AND 5 AND 8
10.
‘‘1989/01/01’’[PDAT] : ‘‘3000/12/31’’[PDAT]
11.
9 AND 10
Search strategy in Embase (Dec 10, 2014) 1.
‘adult’/exp OR ‘late life’:ab,ti OR late*life:ab,ti OR ‘later in life’:ab,ti
2.
‘child’/exp OR ‘childhood’/exp OR ‘early life’:ab,ti
3.
‘migrant’/exp OR ‘ancestry group’/exp
4.
‘non communicable disease’/exp OR ‘stroke’/exp OR ‘heart disease’/exp OR ‘hypertension’/exp OR ‘non insulin dependent diabetes mellitus’/exp
5.
1 AND 2 AND 3 AND 4
6.
5 AND [1989-2014]/py
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20. Smits MM, Boyko EJ, Utzschneider KM et al (2012) Arm length is associated with type 2 diabetes mellitus in Japanese-Americans. Diabetologia 55:1679–1684 21. Subramanyam MA, James SA, Diez-Roux AV et al (2013) Socioeconomic status, John Henryism and blood pressure among African-Americans in the Jackson Heart Study. Soc Sci Med 93:139–146 22. Pettitt DJ, Forman MR, Hanson RL, Knowler WC, Bennett PH (1997) Breastfeeding and incidence of non-insulin-dependent diabetes mellitus in Pima Indians. Lancet 350:166–168 23. Valdez R, Athens MA, Thompson GH, Bradshaw BS, Stern MP (1994) Birthweight and adult health outcomes in a biethnic population in the USA. Diabetologia 37:624–631 24. James SA, Van Hoewyk J, Belli RF, Strogatz DS, Williams DR, Raghunathan TE (2006) Life-course socioeconomic position and hypertension in African American men: The Pitt County Study. Am J Public Health 96:812–817 25. Spann SJ, Gillespie CF, Davis JS et al (2014) The association between childhood trauma and lipid levels in an adult low-income, minority population. Gen Hosp Psychiat 36:150–155 26. Dreyfus JG, Lutsey PL, Huxley R et al (2012) Age at menarche and risk of type 2 diabetes among African-American and White women in the Atherosclerosis Risk in Communities (ARIC) Study. Diabetologia 55:2371–2380 27. Franks PW, Hanson RL, Knowler WC et al (2007) Childhood predictors of young-onset type 2 diabetes. Diabetes 56:2964–2972 28. De Courten MP, Pettitt DJ, Knowler WC (1996) Hypertension in Pima Indians: prevalence and predictors. Public Health Rep 111(Suppl):40–43 29. Glymour MM, Avendan˜o M, Haas S, Berkman LF (2008) Lifecourse social conditions and racial disparities in incidence of first stroke. Ann Epidemiol 18:904–912 30. Robinson WR, Gordon-Larsen P, Kaufman JS, Suchindran CM, Stevens J (2009) The female-male disparity in obesity prevalence among black American young adults: contributions of sociodemographic characteristics of the childhood family. Am J Clin Nutr 89:1204–1212 31. Lucove JC, Kaufman JS, James SA (2007) Association between adult and childhood socioeconomic status and prevalence of the metabolic syndrome in African Americans: the pitt county study. Am J Public Health 97:234–236 32. Pollitt RA, Kaufman JS, Rose KM, Diez-Roux AV, Zeng D, Heiss G (2008) Cumulative life course and adult socioeconomic status and markers of inflammation in adulthood. J Epidemiol CommunityHealth 62:484–491 33. Roberts CB, Couper DJ, Chang PP, James SA, Rosamond WD, Heiss G (2010) Influence of life-course socioeconomic position on incident heart failure in blacks and whites: the atherosclerosis risk in communities Study. Am J Epidemiol 172:717–727 34. Falkner B, Hulman S, Kushner H (1998) Birth weight versus childhood growth as determinants of adult blood pressure. Hypertens 31:145–150 35. The NS, Richardson AS, Gordon-Larsen P (2013) Timing and duration of obesity in relation to diabetes: findings from an ethnically diverse, nationally representative sample. Diabetes Care 36:865–872 36. Galobardes B, Lynch JW, Smith GD (2004) Childhood socioeconomic circumstances and cause-specific mortality in adulthood: systematic review and interpretation. Epidemiol Rev 26:7–21 37. Nandi A, Glymour MM, Kawachi I, VanderWeele TJ (2012) Using marginal structural models to estimate the direct effect of adverse childhood social conditions on onset of heart disease, diabetes, and stroke. Epidemiol 23:223–232
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46. Chen W, Srinivasan SR, Li S, Xu J, Berenson GS (2007) Clustering of long-term trends in metabolic syndrome variables from childhood to adulthood in Blacks and Whites: the Bogalusa Heart Study. Am J Epidemiol 166:527–533 47. Chen W, Srinivasan SR, Ruan L, Mei H, Berenson GS (2011) Adult hypertension is associated with blood pressure variability in childhood in blacks and whites: the bogalusa heart study. Am J Hypertens 24:77–82 48. Eriksson M, Carlberg B, Jansson JH (2012) Comparison of blood pressure measurements between an automated oscillometric device and a Hawksley random-zero sphygmomanometer in the northern Sweden MONICA study. Blood Press Monit 17:164–170 49. Goonasekera CD, Dillon MJ (1995) Random zero sphygmomanometer versus automatic oscillometric blood pressure monitor; is either the instrument of choice? J Hum Hypertens 9:885–889 50. Agyemang C, Bhopal R, Bruijnzeels M (2005) Negro, Black, Black African, African Caribbean, African American or what? Labelling African origin populations in the health arena in the 21st century. J Epidemiol Community Health 59:1014–1018 51. Bhopal R, Unwin N, White M et al (1999) Heterogeneity of coronary heart disease risk factors in Indian, Pakistani, Bangladeshi, and European origin populations: cross sectional study. BMJ 319:215–220
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IM - REVIEW
The influence of early-life conditions on cardiovascular disease later in life among ethnic minority populations: a systematic review Rimke Bijker1 • Charles Agyemang1
Received: 1 May 2015 / Accepted: 10 June 2015 Ó SIMI 2015
Abstract Ethnic minority groups are disproportionately affected by cardiovascular diseases (CVDs). The reasons for the high prevalence of CVD in ethnic minority groups are not fully understood. Recently, the importance of earlylife developmental factors and their impact on CVDs in adulthood is increasingly being recognised, but little is known about this among ethnic minority groups. Therefore, the current paper aimed to fill this knowledge gap by reviewing the available literature to assess the influence of early-life conditions on CVDs and its risk factors in ethnic minority populations residing in Western countries. A systematic search was performed in PubMed and EMBASE between 1989 and 2014. In total, 1418 studies were identified of which 19 met the inclusion criteria. Six studies investigated the relationship between early-life anthropometrics and CVD risk factors of which all except one found significant associations between the assessed anthropometric measures and CVD risk factors. Seven studies evaluated the influence of childhood socio-economic status (SES) on CVD and risk factors of which five found significant associations between childhood SES measures and CVD risk factors. Five studies investigated the relationship between other early-life conditions including early-life nutrition, physical development, and childhood psychosocial conditions, and CVD risk factors. Four of these studies found significant associations between the assessed childhood conditions and CVD risk factors. This review reinforces the importance of early-life conditions on adult
& Charles Agyemang [email protected] 1
Department of Public Health, Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands
CVD in ethnic minority groups. Improvement of early-life conditions among ethnic minority groups may contribute to reducing CVD risk in these populations. Keywords Early-life condition Cardiovascular disease Ethnic minorities Ethnic health
Introduction Findings from the Global Burden of Disease study 2010 indicate that worldwide, more than half of all Disability adjusted life years (DALYs) are due to cardiovascular diseases (CVDs), such as ischemic heart disease and stroke [1]. A relatively high proportion of this disease burden in high-income countries is attributable to intermediate risk factors, such as high blood pressure and obesity [2]. Ethnic minority groups have been particularly affected by CVDs and its intermediate risk factors compared with the European host populations for reasons that are not well understood [3–6]. Hence, there is a need for knowledge on how CVD develops, in particular, in ethnic minority populations. Recently, the importance of early-life developmental factors and their influence on CVDs in adulthood is increasingly being recognised [7–9]. A wide variety of studies have been conducted to evaluate the influence of early-life conditions on CVDs in adulthood, and various literature reviews have summarised the findings in both Western and non-Western countries [10–13]. However, none of these reviews focused explicitly on ethnic minorities. The current paper aimed to fill this gap by reviewing the available literature to assess the influence of early-life conditions on CVDs, principally heart disease and stroke and its risk factors (hypertension, diabetes,
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obesity/adiposity, dyslipidaemia and diabetes) in ethnic minority populations residing in Western countries (i.e. the USA, Canada, Western Europe, Australia and New Zealand). Early life in this paper is defined as the time frame from birth up to approximately 16 years.
Methods A systematic search was performed with scientific literature databases (PubMed and EMBASE) using combinations of the key words ‘‘cardiovascular disease’’, ‘‘early life’’, ‘‘later in life’’, ‘‘ethnic minority population’’ and alternatives of these words. A specific search syntax was developed in collaboration with an experienced librarian (see Table 2 in ‘‘Appendix’’). The search was restricted to papers published between 1989 and 2014, since the theory of early-life conditions as determinants of late-life health originates from a study conducted in 1989, by Barker and colleagues [14]. A manual search was conducted to identify further relevant studies. The search results were screened by title and abstract for potential eligibility. Studies published in the English language were eligible for inclusion if they evaluated the relationship between early-life conditions and CVDs later in life in
ethnic minority populations and had a longitudinal or cross-sectional design. Studies were excluded if they were conducted in non-Western settings; had a main outcome other than CVDs or its intermediate risk factors; or did not focus on the association between early-life conditions and outcome later in life. Furthermore, studies were excluded if they combined ethnic minority populations with the host majority populations. Full texts were obtained and screened if articles met the inclusion criteria. If articles were excluded during the full-text screening, reasons for exclusion were documented (Fig. 1). Data extraction and synthesis Several steps were followed to extract the data. Firstly, a data extraction form was developed in Microsoft Excel to record relevant study details. Data were extracted on study design, setting, population, early-life conditions, outcomes, other variables included in the analysis and main findings of the study. Secondly, studies were categorised according to the early-life conditions they investigated. The study characteristics and the results were summarised by early-life condition and grouped according to health outcome if applicable. Furthermore, if studies compared ethnic minority populations with a host
Identification
Fig. 1 Study selection Records identified through database searching (n= 1416)
Additional records identified through other sources (n = 2)
Included
Eligibility
Screening
Records after duplicates removed (n = 1293)
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Records screened (n = 1293)
Records excluded (n = 1255)
Full-text articles assessed for eligibility (n = 38)
Full-text articles excluded, with reasons
Studies included in qualitative synthesis (n = 19)
-
Results not stratified by ethnicity (n =8) No CVD (risk) specified (n=3) No cohort/cross-sectional study (n=1) No focus association early life and CVD (n=7)
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population group, differences and similarities were described whenever feasible.
use or exercise) [19, 20, 24–26, 32]; and six for family history of CVD [19, 20, 22, 26, 32, 35]. One study did not adjust for any form of confounding [34].
Note on ethnicity Early-life anthropometrics and CVDs There is no consensus on appropriate terms for the scientific study of health by ethnicity, and published guidelines are yet to be widely adopted. Ethnicity usually refers to a group that shares a range of cultural characteristics, such as ancestry, religion, language and diet [15]. However, ethnicity and the biological term race are often used interchangeably and inappropriately [16]. In Western countries, the term ethnic minority group is commonly used to indicate non-White populations of non-European descent [15]. Yet, methods by which participants are categorised into a specific ethnic minority group are often unclear [16]. This review follows present general conventions in terminology of ethnic groups. Several terms, such as ‘‘blacks’’ and ‘‘black Americans’’, were used by authors to refer to African origin populations in the USA studies. For simplicity, we used the term ‘‘African Americans’’ to refer to African origin populations in the USA.
Results In total, 1418 studies were identified from the systematic and manual searches. Of these, 38 full-text articles were assessed for eligibility, of which 19 studies were excluded because they did not meet the selection criteria (Fig. 1). Of the remaining 19 studies (Table 1), 17 were conducted in the USA and two in Australia [17, 18]. Eight studies had a cross-sectional design [17, 19–25], whereas 11 studies were of longitudinal nature [18, 26–35]. Six studies were based on African Americans [19, 21, 24, 25, 31, 34], three were based on Pima Indians [22, 27, 28], one on Japanese Americans [20] and two on Australian aboriginals [17, 18]. In the remaining seven studies, the population entailed both African-American and White participants [26, 29, 30, 32, 33, 35], or Mexican-American and non-Hispanic-White participants [23], allowing for direct comparisons between the groups. Study sample sizes ranged from 134 to 3978 participants in the ethnic minority populations and from 128 to 17,642 participants in the White populations. Several exposures were assessed in the included studies, such as early-life anthropometrics in seven studies [17, 18, 23, 27, 28, 34, 35], childhood SES in seven studies [21, 24, 29– 33] and other childhood influences in five studies [19, 20, 22, 25, 26]. The studies differed in inclusion of established risk factors for CVDs. Eight studies adjusted their analyses for adult socio-economic status (SES) [19, 21, 24, 26, 31– 33, 35]; seven for presence of risk factors in adulthood [17, 19, 20, 24, 26, 32, 33]; six for lifestyle (smoking, alcohol
Seven studies investigated the relationship between earlylife anthropometrics and CVD risk factors [17, 18, 23, 27, 28, 34, 35]. All studies found significant associations between the assessed anthropometric measures and outcomes, except for one among African Americans [34]. However, the findings varied by ethnicity and gender. For example, one study compared Mexican-American and non-Hispanic-White men and women regarding the influence of birthweight on subscapular-to-triceps-skinfold ratio, blood pressure, fasting insulin, fasting glucose and lipids at age 25–64 [23]. Among Mexican-American women, low birthweight was related to most risk factors, whereas no such relations were found among Mexican-American men. Similarly, no relationships were found among White-American men and women except for a significant inverse relationship between birthweight and triglycerides in men. On the contrary, one study among Australian Aboriginals found a positive association between birthweight and fasting glucose levels [18]. Furthermore, in another study that assessed the effect of obesity on diabetes among African Americans and White Americans, African Americans who were obese in early adolescence had over a twofold risk of developing diabetes compared with those without obesity, whereas no significant associations were found in White Americans. [35]. Childhood SES Seven studies assessed the influence of childhood SES on CVDs (heart failure [33] and stroke [29]) and risk factors (metabolic syndrome [31], obesity [30], hypertension [21, 24] and inflammatory risk markers [32]) later in life. Childhood SES was based on a variety of measures including parental education [21, 29, 30, 32, 33], parental occupation [24, 29, 31–33], home ownership of parents [33], SES of the neighbourhood that a child was exposed to [32], number of rooms in the childhood home and access to household assets [21], family structure characteristics [30] and adult height as a marker of childhood SES [29]. Three studies combined variables into a composite measure to specify childhood SES [21, 29, 32], and three studies created variables to asses SES over the course of childhood to adulthood [21, 24, 32]. Of the seven studies, five found associations between at least some of the childhood SES measures and the CVD and risk factor [21, 24, 29, 30, 32], whereas two studies did not find any significant associations [31, 33]. Interestingly, one of these two studies used a sole indicator of childhood SES (i.e. parental occupation) and assessed its association with
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Setting
USA
Australia
Australia
USA
USA
Falkner et al. [34]
Singh and Hoy [17]
Sayers et al. [18]
Valdez et al. [23]
De Courten et al. [28]
Early-life anthropometrics
References
Longitudinal
Cross-sectional, San Antonio Heart Study
Longitudinal, Aboriginal Birth Cohort Study
Cross-sectional
Longitudinal, PCP Philadelphia
Design, part of larger study
188 Pima Indians, age 5–9 years, followed up at age 18–24 years
413 Mexican Americans and 128 non-Hispanic White Americans, age 25–64 years
134 Aboriginals, followed from birth up to mean age 18.3
767 Australian Aboriginals, age 7–43 years
137 African Americans, followed from birth up to age 28 years
Population, age, follow-up period (if applicable)
Table 1 Description of studies included in the review
Childhood mean blood pressure, relative weight (age standardised BMI)
Birth weight
Birth weight
Birth weight (ponderal index)
Birth weight and birth adiposity (ponderal index)
Exposure
Hypertension in adulthood (additional analysis)
Mean blood pressure in adulthood
Metabolic, anthropometric, heamodynamic characteristics
Fasting glucose and insulin levels
Current blood pressure
Adult blood pressure
Outcome
No significant association was found between childhood relative weight and hypertension in adulthood.
Adjusted for age.
Additional analysis performed on 67 men in population (no data available for women).
Relative weight was associated with mean blood pressure (p \ 0.05, no effect size provided).
Adjusted for age.
In non-Hispanic White-American men, participants in the lowest birth weight tertile had higher plasma triglycerides (p, 0.025).
In Mexican-American men, no significant associations were found between birth weight and the assessed characteristics.
In non-Hispanic White-American women, no significant associations were found between birth weight and the assessed characteristics.
In Mexican-American women, participants in the lowest birth weight tertile had higher subscapular-to-triceps-skinfold ratios (p, 0025); SBP (p, 0.020); DBP (p, 0.033); fasting insulin (p, 0.001); and fasting glucose (p, 0.040).
Adjusted for age, stratified by sex and categorised by birth weight.
No significant association was found between birth weight and insulin levels.
1 kg increase of birth weight was associated with 7 % rise of fasting glucose level (p, 0.002).
1 kg increase of birth weight was associated with 2.9 mmHg decrease in systolic BP (95 % CI 0.3–5.5 mmHg). Adjusted for age, sex and gestational age.
Adjusted for age, sex and current weight.
No significant correlation was found between birth weight and adult BP. No significant correlation was found between birth ponderal index and adult BP.
Not adjusted for other variables.
Main findings
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USA
Franks et al. [27]
USA
USA
USA
Lucove et al. [31]
Roberts et al. [33]
Robinson et al. [30]
Childhood SES
The et al. [35]
Setting
References
Table 1 continued
Longitudinal, Add Health
Longitudinal, ARIC
Longitudinal, Pitt County Study
Longitudinal, Add Health
Longitudinal
Design, part of larger study
2096 African American and 5651 White nonimmigrant American young adults, age 11–19, followed up for 7 years
8519 White Americans, mean age 53.9 years, median follow-up period 16.2 years
2503 African Americans, mean age 52.8 years, median follow-up period 16.0 years
1407 African Americans, age 25–50, followed up for 13 years
2096 African Americans and 6218 White Americans, age 11-21 followed up until age 24–34
1604 Pima Indians, age 5–19 years, median follow-up period 5.5 years
Population, age, follow-up period (if applicable)
Childhood sociodemographic characteristics (parental education, family structure, female caregiver’s age at child’s birth, number of minors in household, number of siblings, birth order)
Early-life SEP (parental education, occupation and home ownership of parents/caregivers)
Parental occupation
Adolescent obesity onset (before or after age 16 years)
Waist circumference
Exposure
Obesity (gender disparity)
Heart failure
Metabolic syndrome
Prevalent diabetes
Incident diabetes
Outcome
In White Americans, there was no significant gender disparity.
In African Americans, parental education was strongly associated with the gender disparity in obesity. African-American women from loweducation families were at the greatest risk of obesity, whereas African-American men from low-education families were at the lowest risk for obesity.
Adjusted for age.
No association was found between early-life SEP and heart failure in neither African Americans nor White Americans.
Adjusted for age, sex, study centre, young adulthood SEP, mid-to-older adulthood SEP and heart failure risk factors.
No significant association was found between parental occupation and metabolic syndrome.
Adjusted for age, sex and adult SES.
In White Americans, no significant association was found for adolescent obesity onset and prevalent obesity.
In African Americans, adolescent obesity (onset \ 16 years) was associated with increased prevalence of diabetes (OR 2.25; 95 % CI 1.01–4.98) as compared to adulthood obesity onset.
Adjusted for age, education, sex, parental history of diabetes.
1 SD difference in waist circumference (HRR 2.2; CI 1.8–2.7) and BMI (HRR 2.2; CI 1.6–2.2) at young age were strong predictor traits of incident diabetes.
All predictor traits were associated with incident diabetes.
Adjusted for age, sex and Pima Indian heritage.
Main findings
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Setting
USA
USA
USA
References
Glymour et al. [29]
James et al. [24]
Subramanyam et al. [21]
Table 1 continued
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Cross-sectional, Jackson Heart Study
Cross-sectional, Pitt County Study
Longitudinal, Health and Retirement Study
Design, part of larger study
3978 African Americans, age 21–95 years
379 African-American men, age 25–50, followed up for 13 years
3019 African Americans and 17,642 White Americans, age 50? , mean follow-up period 9.3 and 9.5 years, respectively
Population, age, follow-up period (if applicable)
Childhood SES (based on parental education, number of rooms in the home and access during childhood to households assets such as indoor plumbing, refrigerator and tv) and cumulative SES
Life-course SEP (childhood/adult occupation)
Childhood SEP (parental occupation)
Parental SES (mothers education, fathers education and fathers occupation), adult height and retrospective health
Exposure
Hypertension
Hypertension
First stroke onset
Outcome
In women, participants categorised in the middle childhood SES tertile (PR 1.09; 95 % CI 1.00–1.20) and in the middle and lowest cumulative SES tertile (PR 1.09; 95 % CI 1.00–1.20 and PR 1.16; 95 % CI 1.06–1.27, respectively) had a higher prevalence of hypertension than women in the highest SES tertiles.
In men, no significant association was found between childhood SES or cumulative SES and hypertension.
Adjusted for age and adult SES; stratified by sex.
High/low SEP (OR 5.87; 95 % CI 1.25–27.49) and low/low life-course SEP (OR 7.27; 95 % CI 1.91–27.51) were associated with hypertension as compared to high/high life-course SEP.
No significant associations were found between childhood SEP and hypertension.
In White American, father’s education less than 8 years (HR 1.24; 95 % CI 1.03–1.48) as compared to longer than 8 years and fair or poor childhood health as compared to good, very good or excellent health (HR 1.31; 95 % CI 1.09–1.58) and the composite measure of low parental SES (HR 1.27; 95 % CI 1.09–1.48) were associated with first stroke onset. Adjusted for age, BMI, waist-hip ratio, adult SEP, marital status, alcohol, smoking, strenuous exercise, perceived stress, John Henryism, instrumental support, emotional support.
In African Americans, no significant associations were found between any of the exposures and first stroke onset.
Adjusted for age, sex, Southern birth state and Hispanic ethnicity.
Main findings
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USA
Pollitt et al. [32]
USA
USA
Smits et al. [20]
Pettitt et al. [22]
Other early-life influences
Setting
References
Table 1 continued
Cross-sectional, infant feeding data provided in earlier stage
Cross-sectional, JapaneseAmerican Community Diabetes Study
Longitudinal, ARIC? LCSES
Design, part of larger study
720 Pima Indians, age 10–39 years
464 2nd/3rd generation Japanese Americans, mean age men with diabetes 60.9; men without diabetes 49.3; women with diabetes 62.2; and women without diabetes 50.4 years
2761 African Americans and 9081 White Americans, age 45–64 years, retrospectively asked about early life
Population, age, follow-up period (if applicable)
Breastfeeding
Total, upper and fore arm length; total and lower leg length; and height (as markers of early-life environment and development)
Cumulative life course SES based on number of exposures to social class (in childhood, young adulthood and mature adulthood), to level of education (of participant and participant’s father) and to contextual/ neighbourhood-level SES (in childhood, and young and mature adulthood)
Exposure
Type 2 diabetes
Type 2 diabetes
Levels of inflammatory risk markers (fibrinogen, white blood cell count, CRP, van Willebrand factor)
Outcome
Exclusive breastfeeding was associated with less diabetes compared to exclusive bottle feeding (OR 0.41; 95 % CI 0.18–0.93).
Adjusted for sex, age, birth weight, parental diabetes, birth year.
No significant associations were found between fore arm length; total and lower leg length; and height, and type 2 diabetes.
1 SD increase in total arm length (OR 0.49; 95 % CI 0.29–0.84) and upper arm length (OR 0.56; 95 % CI 0.36–0.87) were inversely related to type 2 diabetes.
Adjusted for age, sex, weight, height (only in models regarding arm length) intra-abdominal fat area, family history of diabetes and smoking status.
In White-American participants, higher cumulative exposure to lowest education group and worker class group were associated with fibrinogen (p for trend, 0.0054 and 0.02, respectively) and with white blood cell count (p for trend, 0.0014 and 0.04, respectively).
In African-American participants, the only association was between higher cumulative exposure to worker class group and CRP (p for trend, 0.027).
Adjusted for age, sex, study centre, adult SES measures, HDL-C, LDL-Cl, BMI, hypertension and hypertension medication, family history of CVD, diabetes status, alcohol intake, smoking status and cigarette-years smoked.
Main findings
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USA
USA
USA
Dreyfus et al. [26]
Spann et al. [25]
Barrington et al. [19]
Cross-sectional, Howard University Family Study
Cross-sectional
Longitudinal, ARIC
Design, part of larger study
515 African-American men, mean age 48 years
452 African Americans, age [ 18 years
2505 African-American and 5986 White-American women, mean age 53,3 and 54.0 years, respectively, followed up for 9 years
Population, age, follow-up period (if applicable)
Socio-familiar conditions (years lived with both parents)
Childhood trauma
Age at menarche
Exposure
Hypertension
HDL-C/LDL-C ratios
Type 2 diabetes
Outcome
Living with both parents (1–12 years) was protective for hypertension later in life (OR 0.54; 95 % CI 0.30–0.99) as compared to not having lived with both parents.
Adjusted for age, education, marital status, employment, smoking, sodium/potassium ratio, HDL-C, obesity, diabetes mellitus and family history of hypertension.
In women, no significant associations were found between childhood trauma and HDL-C/LDL-C ratio.
In men, higher childhood trauma levels were inversely associated with HDL-C/LDL-C ratio (b, -0.179; p, 0.038).
Adjusted for age, alcohol use, smoking and adult trauma.
In White-American women, early age at menarche (8–11) was associated with type 2 diabetes (OR 1.41; 95 % CI 1.05–1.89) as compared to menarche at age 13 years.
In African-American women, no significant association was found between age at menarche and type 2 diabetes.
Adjusted for age, study centre, education level, BMI (baseline and at age 25 years), baseline height and waist circumference, smoking status, use of oral contraceptives and family history of diabetes.
Main findings
PCP Perinatal Collaborative Project, Add Health National Longitudinal Study of Adolescent Health, ARIC Atherosclerosis Risk in Communities Study, LC-SES Life Course Socioeconomic Status, Social Context and Cardiovascular Disease Study, BP blood pressure, SBP systolic blood pressure, DBP diastolic blood pressure, SEP socio-economic position, SES socio-economic status, CRP C-reactive protein, HDL-C high-density lipoprotein cholesterol, LDL-C low-density lipoprotein cholesterol, BMI body mass index, CVD cardiovascular disease, A1C test to assess diabetes, mmHG millimetre of mercury, OR odds ratio, p probability, SD standard deviation, HRR hazard rate ratio, CI confidence interval, PR prevalence ratio, HR hazard ratio
Setting
References
Table 1 continued
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metabolic syndrome in an African-American population [31], whilst the other used several separate measures (i.e. parental education, occupation and home ownership of parents) as well as a composite measure to investigate the influence of childhood SES on heart failure in African Americans and White Americans [33]. Furthermore, the association of childhood SES measures with CVDs and risk factors varied by ethnicity and gender. Two studies found distinct differences across ethnic groups in evaluating the effect of childhood SES on stroke and obesity [29, 30]. For instance, differences were found between African Americans and White Americans that were followed up to investigate the gender disparity in obesity [30]. Among African Americans growing up in low-education families, young women were at greatest risk, whereas young men were at lowest risk of developing obesity. Among White Americans, however, no notable difference was found in obesity across gender. Another study assessed the influence of childhood SES (mother’s education, father’s education, father’s occupation, childhood health and height) on stroke risk [29]. Among African Americans, none of the associations yielded significant results when childhood indicators were included in one model, whereas among White Americans, relatively weak associations were found for father’s education less than 8 years and fair or poor childhood health and stroke risk. Likewise, after creating a composite measure for parental SES, low parental SES was associated with stroke risk in White Americans, but not in African Americans. Shorter stature was associated with stroke risk in both groups. The remaining three studies evaluated the influence of life-course SES on hypertension or inflammatory risk markers [21, 24, 32]. Among African-American men, childhood SES alone, measured as parental occupation, did not have an effect on hypertension, whereas life-course SES did (parental and adult occupation) [24]. Participants who maintained a low SES throughout their lives, and those who degraded from a high to a low SES, had a strongly increased risk of hypertension as compared to participants who maintained a high SES. In a comparable study on AfricanAmerican men and women, cumulative SES was created by combining a composite measure of childhood SES and adult SES [21]. No significant effects of childhood or cumulative SES were found in men, whereas in women, those categorised in the middle childhood SES tertile and in the middle and lowest cumulative SES tertile had a slightly higher prevalence of hypertension than women in the highest SES tertiles. In addition, measures of life-course SES (i.e. number of exposures to social class and neighbourhood-level SES throughout the course of life and education of participant and participant’s father) and inflammatory risk markers (i.e. fibrinogen, C-reactive protein, white blood cell count and van Willebrand factor) were evaluated in African Americans and White Americans [32].
Among African Americans, a weak association was found for those with high cumulative exposure to working class group and C-reactive protein. For White Americans on the other hand, high cumulative exposure to lowest education group and working class group were associated with fibrinogen and white blood cell count. Other early-life influences Five studies were identified that investigated the influence of other early-life conditions on CVD and risk factors later in life, of which all except one found significant effects of their exposure variables among ethnic minorities [19, 20, 22, 26]. Three of these studies assessed the influence of physical development and nutrition on diabetes [20, 22, 25]. For instance, arm and leg length were investigated as proxy measures for early-life nutrition in Japanese Americans [20]. After adjusting for relevant confounders, total arm length and upper arm length were inversely associated with having diabetes, whereas other measures of limb length were not. In addition, early-life nutrition was assessed as having been breast- or bottle-fed in Pima Indians [22]. Findings indicated that breastfeeding is strongly associated with a decreased risk of developing diabetes independently of birth weight and parental diabetes. Furthermore, the effect of age at menarche was studied in African-American and WhiteAmerican women [26]. The findings reveal that having diabetes was independently associated with early age of menarche (8–11 years as compared to 13 years) in WhiteAmerican women, but not in African-American women. The remaining studies investigated the relationship between psychosocial conditions in childhood and CVD later in life. For instance, one study assessing the association between childhood trauma and cholesterol levels found that among men, but not among women, higher levels of childhood trauma were associated with reduced high-density lipoprotein/low-density lipoprotein ratios [25]. Another study examined childhood living situation in relation to hypertension in African-American men [19]. The study found that living with both parents for 1–12 years (as opposed to living with only one parent) is protective of hypertension later in life independent of confounding factors.
Discussion Key findings This literature review assessed early-life conditions related to late-life CVD and risk factors in ethnic minority populations residing in Western settings. The findings suggest that for these populations, being born with high birthweight and receiving breastfeeding are protective of CVDs and its
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risk factors, whereas childhood overweight has an adverse effect on CVDs later in life. Furthermore, low childhood SES, especially when accompanied by low SES in adulthood, also has an adverse effect on CVDs, although the findings on this topic were somewhat inconsistent and tended to vary by ethnicity and gender. Discussion of the key findings Numerous reviews have found evidence for the contributions of early-life influence on CVDs and risk factors later in life. For instance, low childhood SES has been linked to conditions such as elevated blood pressure, diabetes, heart disease, and CVD mortality in low- and middle-income countries as well as in high-income countries [10, 11, 36]. It has been acknowledged though, that the effect of childhood SES on adult health appears to be greatly mediated by adult SES. The findings of our review, however, suggest an important role of SES throughout the course of life on CVDs and risk factors among ethnic minorities. Of note, findings from the Health and Retirement study, in which data of different ethnic groups were pooled using a novel modelling approach, indicate that the effect of childhood SES on CVDs and risk factors are independent of adult SES [37]. These findings suggest that although adult SES may be an important determinant of adult health, the influence of social and economic conditions in early life should not be underestimated in either ethnic minority populations or the population as a whole. In line with reviews that did not distinguish findings by ethnicity, the findings of this review suggest relationships between early-life anthropometrics and CVDs and risk factors [10, 11, 13, 38], although the findings were somewhat inconsistent and tended to differ by ethnicity and gender. The explanations for the variations across ethnic groups and gender are unclear but may relate to differences in lifestyle. For instance, according to the US health statistics for adults, smoking behaviour, alcohol use and physical activity patterns differ between men and women and between ethnic groups [39]. Thus, contrasting findings in the early-life determinants of CVDs might be attributable to confounding of such lifestyle factors later in life, which were not assessed in all studies. With regard to nutrition in infancy, a large body of evidence has been found supporting the protective effects of breastfeeding [11, 38, 40]. This is consistent with the findings among Pima Indians of the one study that this review identified on the topic [22]. Interestingly, a study that compared data of large birth cohorts from five lowand middle-income countries did not find an association between breastfeeding and hypertension or diabetes [41]. As speculated by the authors of this study, contrasting findings may be explained by different categorisation of
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breastfeeding patterns and the definition of complementary foods. These findings suggest the need for standardisation of data collection methods on early-life conditions to assist the comparability of data across studies. Ethnic minority populations are at increased risk for CVDs, yet statistical models are not commonly stratified by ethnicity to further investigate health disparities [42]. Overall, this review found that the effect of early-life conditions on CVDs in specifically ethnic minority populations was evaluated in a modest number of articles. Almost all of these studies were conducted in the USA. Remarkably, none of the identified studies focused on ethnic minority populations residing in Europe, even though an increasing part of the European population is of non-European descent and ethnic health disparities are greatly apparent [43]. Furthermore, a multitude of studies have indicated relationships between other early-life conditions and CVDs. Some examples are the protective effects of low sodium and protein intake [11, 12, 44] and the harmful effects of parental smoking [45]. The current review was not able to identify any studies that focused on these early-life conditions in ethnic minority populations. The dearth of studies on these topics underscores the need for more studies on early-life conditions and their impact on health outcomes among ethnic minority populations in Europe. Although it is difficult to unravel the complexity of the relationships between early-life conditions and CVDs and their interconnectedness with adult risk factors, recommendations can be drawn from our current findings. Foremost, interventions to reduce health inequalities should pay attention to early-life conditions. The relevance of this is emphasised by evidence showing ‘tracking’ of CVD risk factors. For example, metabolic risk factors such as obesity, insulin resistance, hypertension, and dyslipidaemia tend to cluster from childhood to adulthood [46]. In addition, variability of childhood blood pressure has been associated with hypertension in both African Americans and White Americans [47]. These findings suggest that once unfavourable health outcomes are established, they tend to persist into adulthood and increase future risk of CVDs. Thus, it is crucial to tackle intermediate risk factors as early as possible. In order to adequately address the harmful influence of adverse childhood conditions, further research is warranted into these issues in ethnic minority populations.
Limitations Some limitations should be noted regarding the definitions of early-life conditions and CVDs. Firstly, in most studies, information on early-life conditions was recorded retrospectively by means of self-report [19, 21, 24–26, 29, 31– 33], which are subjected to recall bias. Furthermore, some of
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the studies had small sample sizes. It is possible that these studies were not sufficiently powered to detect significant associations between some of the early-life conditions and CVDs. Secondly, diverse measures were used to assess early-life conditions. For example, childhood SES was measured using a variety of indicators, such as parental education, father’s occupation, and number of rooms in a household. The absence of one congruent measure to assess early-life conditions makes it challenging to compare findings across studies and draw well-founded conclusions. Likewise, the procedures through which outcomes were assessed varied between studies. For instance, the reviewed studies measured blood pressure utilising sphygmomanometers [21, 24, 28, 34] or oscillometric devices [17, 19]. These two methods of measurement are known to obtain different blood pressure results [48, 49]. Hence, it is difficult to compare findings between studies. Another important limitation concerns the use of terms relating to ethnic groups. It should be acknowledged that, although commonly used, some of these terms are broad and unspecific, relating to a heterogeneous group of individuals. For instance, the term African American often refers to people whose ancestors have been living in the USA for multiple centuries as well as more recent immigrants from Africa and the Caribbean [50]. Similarly, the White population can be divided into subgroups with regard to their customs and living style, with some subgroups being more prone to disease than others [15]. As such, using unspecific ethnic labels for heterogeneous population groups might
result in attenuating or abolishing effects that would have been apparent when stratifying by population group [51].
Conclusion In conclusion, this review has assembled the current knowledge available on the influence of early-life conditions on CVD and risk factors in ethnic minority populations. The findings suggest that conditions in young life are indeed important determinants of future cardiovascular health in ethnic minority groups, even though results vary by ethnicity and gender. Undoubtedly, knowledge in this area needs to be extended to reach firmer conclusions about the contribution of early-life conditions to the ethnic health inequalities. In turn, interventions to thwart CVDs early in life need to be tailored to the target populations. Conflict of interest Authors declare they have no conflict of interest. Statement of human and animal rights This article does not contain any studies with animals performed by any of the authors. Informed consent
None.
Appendix See Table 2.
Table 2 Search Strategies Search strategy in PubMed (Dec 10, 2014) 1.
‘‘Adult’’[Mesh] OR ‘‘later in life’’[tiab] OR late*life[tiab]
2.
child*[tw] OR schoolchild*[tw] OR infan*[tw] OR pediatri*[tw] OR paediatr*[tw] OR neonat*[tw] OR boy[tw] OR boys[tw] OR boyhood[tw] OR girl[tw] OR girls[tw] OR girlhood[tw] OR baby[tw] OR babies[tw] OR toddler*[tw] OR newborn*[tw] OR postneonat*[tw] OR postnat*[tw] OR preschool*[tw] OR ‘‘Early life’’[tiab]
3.
‘‘Transients and Migrants’’[Mesh] OR ‘‘Emigrants and Immigrants’’[Mesh] OR ‘‘Ethnic Groups’’[Mesh]
4.
immigrant*[tiab] OR migrant*[tiab] OR ethnic*[tiab] OR minorit*[tiab] NOT medline[sb]
5.
3 OR 4
6.
(‘‘Chronic Disease’’[Mesh] OR Chronic Disease*[tiab] OR Chronic Illness*[tiab] OR ‘‘Chronically Ill’’[tiab] OR non communicable disease*[tiab] OR NCD*[tiab] OR ‘‘Cerebrovascular Disorders’’[Mesh] OR ‘‘Vascular Diseases’’[Mesh] OR ‘‘Heart Diseases’’[Mesh] OR ‘‘Diabetes Mellitus, Type 2’’[Mesh] OR ‘‘Renal Insufficiency, Chronic’’[Mesh] OR ‘‘Kidney Failure, Chronic’’[Mesh]
7.
‘‘Ischemi*’’[tiab] OR ‘‘Stroke’’[tiab] OR ‘‘Hypertension’’[tiab] OR ‘‘Infarct*’’[tiab] OR ‘‘Diabet*’’[tiab]) OR ‘‘kidney’’[tiab] ‘‘renal’’[tiab] NOT medline[sb]
8.
6 OR 7
9.
1 AND 2 AND 5 AND 8
10.
‘‘1989/01/01’’[PDAT] : ‘‘3000/12/31’’[PDAT]
11.
9 AND 10
Search strategy in Embase (Dec 10, 2014) 1.
‘adult’/exp OR ‘late life’:ab,ti OR late*life:ab,ti OR ‘later in life’:ab,ti
2.
‘child’/exp OR ‘childhood’/exp OR ‘early life’:ab,ti
3.
‘migrant’/exp OR ‘ancestry group’/exp
4.
‘non communicable disease’/exp OR ‘stroke’/exp OR ‘heart disease’/exp OR ‘hypertension’/exp OR ‘non insulin dependent diabetes mellitus’/exp
5.
1 AND 2 AND 3 AND 4
6.
5 AND [1989-2014]/py
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