Clinical and Experimental Hypertension
ISSN: 1064-1963 (Print) 1525-6006 (Online) Journal homepage: http://www.tandfonline.com/loi/iceh20
High prevalence of metabolic syndrome in a middle-aged and elderly population with prehypertension in Tianjin Wei Yao, Yuemin Sun, Xuechun Wang, Quan Si, Huili Chen & Zheng Wan To cite this article: Wei Yao, Yuemin Sun, Xuechun Wang, Quan Si, Huili Chen & Zheng Wan (2015) High prevalence of metabolic syndrome in a middle-aged and elderly population with prehypertension in Tianjin, Clinical and Experimental Hypertension, 37:5, 369-374, DOI: 10.3109/10641963.2014.977487 To link to this article: http://dx.doi.org/10.3109/10641963.2014.977487
Published online: 12 Dec 2014.
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Date: 05 October 2015, At: 11:33
http://informahealthcare.com/ceh ISSN: 1064-1963 (print), 1525-6006 (electronic) Clin Exp Hypertens, 2015; 37(5): 369–374 ! 2015 Informa Healthcare USA, Inc. DOI: 10.3109/10641963.2014.977487
High prevalence of metabolic syndrome in a middle-aged and elderly population with prehypertension in Tianjin Wei Yao, Yuemin Sun, Xuechun Wang, Quan Si, Huili Chen, and Zheng Wan
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Department of Cardiology, Tianjin Medical University General Hospital, Tianjin Medial University, Tianjin, China
Abstract
Keywords
Background: Prehypertension has been reported as being correlated with future cardiovascular risk and end-organ damage in middle-aged and elderly persons, and also playing an important role in metabolic syndrome (MetS). The association between prehypertension and MetS has rarely been reported among urban adults in Tianjin, China. Methods: In this cross-sectional study, a total of 1176 participants aged 40–70 years (524 males and 652 females) were enrolled after excluding participants with hypertension or treated hypertension. Participants were divided into two groups [optimal blood pressure (BP) and prehypertension] based on the classification of BP from the JNC-7. The definition of MetS was as per the International Diabetes Federation standard. An adjusted logistic regression model was used to assess relationships between prehypertension and MetS. Results: The prehypertension group had a significantly higher odds ratio (OR) than the optimal BP group for abnormal waist circumference (WC), fasting plasma glucose (FPG) and triglycerides (TG). In addition, the prehypertension group had a higher OR (3.12; 95% confidence interval 2.34–4.18) for having MetS after adjusting for potential confounders. Conclusions: The risk of having MetS was significantly associated with prehypertension in middle-aged and elderly persons in Tianjin. Stricter control of BP in this age group is warranted.
Metabolic syndrome, prehypertension, risk factor, middle-aged and elderly, primary prevention
Introduction Metabolic syndrome (MetS) is a complex medical disorder comprising five inter-related risk factors within an individual: obesity, hypertension, hypertriglyceridemia, low high-density lipoprotein cholesterol (HDL-c) and hyperglycemia (1,2). It is a growing public health issue, with approximately one-fourth of the world’s adult population having this disorder (3). In 2000, the prevalence of MetS in China was 15.1% (4). From 2007 to 2012, the prevalence of MetS in Tianjin was 19.8, 24.7, 28.8, 29.9, 33.4 and 34.4%, respectively (5). In 2008, the prevalence of abdominal obesity, elevated triglycerides (TG), reduced HDL-c, elevated blood pressure (BP) and elevated fasting plasma glucose (FPG) in Beijing was 44.6, 23.8, 33.9, 49.6 and 21.0% (6). MetS places a tremendous burden not only on the individual’s health, but also on society as a whole (7). Since the establishment of the definition of MetS, many studies have shown that it is a reliable and accurate predictor of future cardiovascular disease (CVD) and diabetes (8–10). Hypertension has been shown to be a key factor in MetS (11). The Framingham Heart Study showed that hypertension
Correspondence: Yuemin Sun, Department of Cardiology, Tianjin Medical University General Hospital, No. 154, Anshan Road, Heping District, Tianjin, 300052, P.R. China. Tel: +86-22-60362779. Fax: +8622-60362427. E-mail: [email protected]
History Received 19 July 2014 Revised 8 October 2014 Accepted 10 October 2014 Published online 11 December 2014
played an important role in MetS and has been reported to be its most commonly associated risk factor (12). In 2003, the seventh report of the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure (JNC-7) proposed a new BP category, designated ‘‘prehypertension’’, of 120–139 mmHg systolic blood pressure (SBP) or 80–89 mmHg diastolic blood pressure (DBP) (13). Some studies had indicated that cardiovascular risk and end-organ damage were already elevated in individuals with prehypertension when compared with those with a BP less than 120/80 mmHg (14). With the recent rapid economic growth and urbanization of China, the prevalence of prehypertension and MetS has significantly increased in concert with extended life expectancy, which now compares favorable with that in many other developed countries worldwide. Tianjin is a city of approximately 10.43 million inhabitants located in the northeast of the North China Plain, facing the Bohai Sea (15). Salt consumption has been shown to be higher in Tianjin because it is near the ocean, and the prevalence of smoking is high (16). These factors may contribute to the particularly high prevalence of hypertension and prehypertension in Tianjin. The present study evaluated the association between prehypertension and MetS among urban adults aged 40 years and older in Tianjin. Although several other studies have described the association between prehypertension and
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MetS, the population on the middle-aged and elderly was few (17–19). In these studies, they included only men or included only women. Through our study, we hope to provide a context for policy planners and health education programs.
Methods
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Study design and study population Study procedures were in accordance with ethical standards of the responsible committee on human experimentation of Tianjin Medical University General Hospital. Tianjin is the sixth largest city of China, located in the northeast region bordering Bohai Bay in the Pacific Ocean. From May 2011 to May 2013, residents living in the six districts of the center of Tianjin City, between the ages of 40 and 70 years, were enrolled after exclusion of participants with hypertension or treated hypertension. In the first stage, six street districts were randomly selected from each city district. In the second stage, recruitment advertisements were posted in these street districts to enroll participants. Two-hundred individuals were enrolled in each street district. All participants were free of self-reported stroke, transient ischemic attack, myocardial infarction, angina or renal failure. A total of 1176 participants including 524 males and 652 females were enrolled in the analysis. The prevalence of selfreported diabetes mellitus was 9.0% (106/1176) in the process of enrollment and 53.8% diabetic subjects received treatment with oral antidiabetic agents and/or insulin. The prevalence of self-reported dyslipidemia was 31.4% in 1176 subjects, 24.9% of whom received antidyslipidemic therapy.
Clin Exp Hypertens, 2015; 37(5): 369–374
and having SBP 5120 mmHg and DBP 580 mmHg. Prehypertension was defined as not being on antihypertensive medication and having an SBP of 120–139 mmHg or DBP of 80–89 mmHg. Body weight and height were measured by trained staff with subjects wearing light clothing and without shoes. The body mass index (BMI) was calculated as weight in kilograms divided by the square of the height in meters. The waist circumference (WC) was measured at the level of 1 cm above the umbilicus. Blood samples were drawn from the antecubital vein after a 10-h fast in the morning. FPG, total cholesterol (TC), TG, HDL-c and low-density lipoprotein cholesterol (LDL-c) were measured using a Hitachi 7180 Automatic Analyzer (Hitachi, Tokyo, Japan), with all analyses performed in accordance with the manufacturer’s recommendations. All blood samples were analyzed in the central laboratory of Tianjin Medical University General Hospital. Definition of MetS The definition of MetS was as per the International Diabetes Federation standard (1), with abdominal obesity defined as WC 90 cm (males) or 80 cm (females) plus any two of the following four abnormal metabolic components: (1) TG 1.7 mmol/l (150 mg/dl) or the use of lipid medications; (2) SBP 130 mmHg and/or DBP 85 mmHg, or the use of antihypertensive medications; (3) FPG 5.6 mmol/l (100 mg/ dl) or the use of diabetes medications; and (4) HDL-c 51.04 mmol/l (40 mg/dl) (males) or 51.29 mmol/l (50 mg/dl) (females).
Data collection and examination
Statistical analysis
An interview-based survey of hypertension was performed using a questionnaire by trained staff. Demographic data, disease history, family history of hypertension, cigarette smoking and alcohol drinking were investigated. Individuals who had smoked 5100 cigarettes during their lifetime were considered non-smoking, those who had smoked 100 cigarettes lifetime and not smoking for at least 1 year were considered past smoking, and those who had smoked 100 cigarettes lifetime and currently smoking were considered current smoking. Current alcohol drinking was defined as consumption of 1 alcoholic drink in the past month. Individuals who had never drinking during their lifetime were considered non-drinking and those who had given up drinking for at least 1 month were considered past drinking. Three BP measurements were performed by two trained doctors while the study participants were seated, using a standard mercury sphygmomanometer according to a standard protocol, after the subjects had been resting for 30 min. Standard cuff bladders (12–13 cm wide and 35 cm long) were used to measure BP, the larger and smaller bladder being available for large (arm circumference432 cm) and thin arms, respectively. The 1st and 5th Korotkoff sounds were recorded as SBP and DBP, respectively; the mean of three measurements was used in the analysis. The classification of normotensive, prehypertensive and hypertensive was based on the classification of BP from the JNC-7 (13). Optimal BP was defined as not being on antihypertensive medication
SPSS version 17.0 software (IBM, Somers, NY) was used to perform all the statistical analyses. Data were expressed as mean ± standard deviation, median with interquartile range, or percentage as appropriate. Comparisons between groups were analyzed by t test or Mann–Whitney U test for measurement data, and 2 test for enumeration data. Multiple logistic regression analysis was used to examine relationships between prehypertension and the prevalence of MetS after adjustment for covariates: age, sex, BMI, smoking status, drinking status, LDL-c, antidiabetic medication and antidyslipidemic medication. An odds ratio (OR) and 95% confidence interval were calculated. All statistical tests were two-tailed, and p values of less than 0.05 were considered statistically significant.
Results Table 1 shows the general characteristics of the study population according to baseline BP. The two groups (optimal BP and prehypertension) differed significantly in all characteristics. The mean age was 55.1 years for the optimal BP group and 57.5 years for the prehypertension group. The prehypertension group showed a significantly higher percentage of male gender, smoking, alcohol drinking, family history of hypertension, diabetes and dyslipidemia in comparison with the optimal BP group. The MetS components of WC, TG, SBP, DBP and FPG in the prehypertension group were significantly higher than those in the optimal BP group, and
MS was increased in people with prehypertension
DOI: 10.3109/10641963.2014.977487
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Table 1. Baseline characteristics of study participants (n ¼ 1176). Optimal BP, n ¼ 584
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Characteristic Age (year) Sex (male, %) Family history of hypertension, (yes, %) Diabetes (yes, %) Antidiabetic medication (yes, %) Dyslipidemia (yes, %) Antidyslipidemic medication (yes, %) Alcohol drinking Current, % Past, % Non, % Smoking Current, % Past, % Non, % BMI (kg/m2) WC (cm) SBP (mmHg) DBP (mmHg) TC (mmol/l) TG, median (mmol/l) HDL-c (mmol/l) LDL-c (mmol/l) FPG, median (mmol/l)
Prehypertension, n ¼ 592
p Valuea
55.1 ± 6.8 220 (37.67) 291 (49.83) 42 (7.19) 23 (54.76) 163 (27.91) 40 (24.54)
57.5 ± 6.7 304 (51.35) 331 (56.01) 64 (10.83) 34 (53.13) 206 (34.80) 52 (25.24)
50.01 50.01 50.01 50.05 40.05 50.05 40.05
184 (31.51) 6 (1.03) 394 (67.47)
254 (42.9) 6 (1.01) 332 (56.08)
50.01 40.05 50.01
71 (12.16) 31 (5.31) 482 (82.53) 23.84 ± 3.07 83.28 ± 9.19 112.33 ± 6.71 72.76 ± 6.15 5.31 ± 1.13 1.22 (0.92, 1.70) 1.48 ± 0.37 3.18 ± 0.92 5.10 (4.70, 5.60)
99 (16.72) 50 (8.45) 443 (74.83) 25.08 ± 3.22 87.57 ± 9.57 128.63 ± 5.16 79.71 ± 6.02 5.41 ± 1.04 1.46 (1.03, 2.10) 1.42 ± 0.39 3.29 ± 0.88 5.30 (5.00, 5.70)
50.05 50.05 50.01 50.01 50.01 50.01 50.01 50.01 50.01b 50.01 50.05 50.01b
BMI body mass index, WC waist circumference, SBP systolic blood pressure, DBP diastolic blood pressure, TC total cholesterol, TG triglycerides, HDL-c high-density lipoprotein cholesterol, LDL-c low-density lipoprotein cholesterol, FPG fasting plasma glucose. a Comparisons between groups were analyzed by t test for measurement data and 2 test for enumeration data. b Comparisons between groups were analyzed by Mann–Whitney U test for TG and FPG.
Table 2. Age-standardized prevalence of MetS (n ¼ 1176).
showed the positive correlation between HDL-c and prehypertension in 50–59 years group (Table 4).
MetS, n (%) Age-group, years 40–49 (n ¼ 189) 50–59 (n ¼ 576) 60 (n ¼ 411) Total
Optimal BP 13 52 36 101
(11.1) (17.7) (20.8) (17.3)
Prehypertension 29 124 108 261
(40.8) (44.0) (45.2) (44.1)
p Valuea
50.0001
a
Comparisons between groups were analyzed by 2 test.
HDL-c was significantly lower than in the optimal BP group. The prehypertension group had an elevated mean BMI, TC and LDL-c compared with the optimal BP group. Table 2 shows the age-standardized prevalence of MetS. The prehypertension group showed a significantly higher percentage of MetS than the optimal BP group. In each age group, the percentage of MetS was significantly higher in the prehypertension group. At least on abnormal MetS component was identified in 81.9% of subjects. The prevalence of the abnormal WC, TG, HDL-c and FPG was 65.0, 32.7, 27.2 and 33.0%, respectively. The crude and adjusted relationships between prehypertension and MetS and its components are shown in Table 3. In the final multivariate models, the prehypertension group had a significantly higher OR for having MetS. Similar relationships were also observed between prehypertension and MetS components, except for HDL-c. Age-stratified analysis
Discussion As the health care system becomes increasingly effective, aging is now a significant issue in China, as in many other developed countries. Therefore, health promotion and disease prevention in the middle-aged and elderly population are important policies for the Department of Health. The purpose of the present study was to determine whether participants with prehypertension would be at higher risk of having MetS. Although many studies have already explored this type of relationship in participants with prehypertension (20–23), very few studies included urban participants from Tianjin. In this study, we demonstrated that even when the BP is within the normal range, it will cause increasing comorbidity concomitant with the rise in BP. Multiple logistic regression analysis was used to evaluate the relationships between prehypertension and MetS, and its components. We adjusted for a number of potentially confounding factors in our analyses. Studies have shown that age and sex are simultaneously related to the incidence of MetS (24), and BMI is an important risk factor that can cause a variety of adverse health effects (25); therefore, we first adjusted for age, sex and BMI. However, adjustment for these factors did not significantly affect the relationship between the prehypertension and MetS, leading us to consider that the direct relationship between prehypertension and MetS was
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independent of age, sex and BMI. We subsequently adjusted for other factors including smoking, drinking status, LDL-c and history of antidiabetic medication and antidyslipidemic medication. However, these adjustments also did not affect the positive relationship between prehypertension and MetS. Table 3. Adjusted relationships between prehypertension and metabolic syndrome and its components.
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Prehypertension
Number with MetS Crude Age-, sex- and BMI-adjusted Multiple adjustedb Mets components Number with elevated WC Crude Age-, sex- and BMI-adjusted Multiple adjustedb Number with elevated TG Crude Age-, sex- and BMI-adjusted Multiple adjustedb Number with reduced HDL-c Crude Age-, sex- and BMI-adjusted Multiple adjustedb Number with elevated FPG Crude Age-, sex- and BMI-adjusted Multiple adjustedb
No, (n ¼ 584)
Yes, (n ¼ 592)
101 Reference Reference Reference
251 3.52 (2.69, 4.61)a 3.07 (2.30, 4.09) 3.12 (2.34, 4.18)
337 Reference Reference Reference 147 Reference Reference Reference 150 Reference Reference Reference 165 Reference Reference Reference
427 1.90 (1.49, 1.53 (1.13, 1.51 (1.11, 238 1.99 (1.56, 1.73 (1.33, 1.72 (1.32, 176 1.22 (0.95, 1.13 (0.86, 1.19 (0.90, 223 1.53 (1.20, 1.40 (1.09, 1.39 (1.08,
2.42) 2.08) 2.06) 2.56) 2.24) 2.24) 1.58) 1.48) 1.56) 1.96) 1.81) 1.80)
BMI body mass index, WC waist circumference, TG triglycerides, HDL-c high-density lipoprotein cholesterol, FPG fasting plasma glucose. a Odds ratios (95% confidence interval) (all such values). b Adjusted for age, sex, BMI, smoking status, drinking stats, LDL-C, antidiabetic medication and antidyslipidemic medication.
In our study, the prevalence of abnormal WC was 65%, higher than that of any other MetS components. Elevated WC was positively correlated with prehypertension. Similar findings can also be found in many other reports. In a cohort of 5050 Chinese men aged from 35 to 74 years, individuals with central obesity and overweight had a significantly higher prevalence of prehypertension than those of normal weight (21). Okosun et al. revealed that abdominal obesity was associated with an increased risk of prehypertension in Americans (26), independent of age, FPG, TC, exercise and current smoking. Our finding further confirmed that participants with prehypertension had a high prevalence of elevated WC. As a result, the importance of controlling obesity should be emphasized for middle-aged and elderly persons in order to prevent hypertension. Numerous studies have shown that FPG is higher in prehypertension and hypertension (21–23,27,28). Subjects with hypertension and prehypertension are more prone to developing diabetes than persons with optimal BP. Similar results were also found in our present study. This is not surprising because insulin resistance (IR) is considered to be the core of MetS (1) and high BP is related to IR. Our data suggested that participants in the prehypertension group had a 1.39-fold increased risk of having elevated FPG than those in the optimal BP group. Therefore, the conclusion could be drawn that middle-aged and elderly persons with prehypertension are at higher risk of developing diabetes in the future. Dyslipidemia also plays a major role in the development of MetS, CVD and diabetes. Our data showed that the HDL-c level was lower in the prehypertension group, but multiple logistic regression analysis showed that HDL-c was
Table 4. Aged-stratified analysis of the relationship between prehypertension and metabolic syndrome and its components.
Age-stratified analysis Number with MetS Crude Age-, sex- and BMI-adjusted Multiple adjustedb Mets components Number with elevated WC Crude Age-, sex- and BMI-adjusted Multiple adjustedb Number with elevated TG Crude Age-, sex- and BMI-adjusted Multiple adjustedb Number with reduced HDL-c Crude Age-, sex- and BMI-adjusted Multiple adjustedb Number with elevated FPG Crude Age-, sex- and BMI-adjusted Multiple adjustedb
40–49 years group (n ¼ 189)
50–59 years group (n ¼ 576)
60 years group (n ¼ 411)
Prehypertension
Prehypertension
Prehypertension
No
Yes
No
Yes
No
Yes
13 Reference Reference Reference
29 5.39 (2.56, 11.35)a 3.35 (1.48, 7.54) 3.45 (1.50, 7.96)
52 Reference Reference Reference
124 3.65 (2.50, 5.35) 3.11 (2.07, 4.67) 3.27 (2.17, 4.95)
36 Reference Reference Reference
98 2.66 (1.70, 4.17) 2.56 (1.67, 4.06) 2.98 (1.83, 4.86)
55 Reference Reference Reference 22 Reference Reference Reference 23 Reference Reference Reference 24 Reference Reference Reference
59 5.11 (2.54, 3.43 (1.49, 3.76 (1.59, 28 2.75 (1.42, 1.71 (1.18, 1.70 (1.09, 27 1.57 (0.81, 1.29 (0.61, 1.25 (0.58, 28 2.47 (1.28, 2.26 (1.08, 2.34 (1.11,
171 Reference Reference Reference 74 Reference Reference Reference 67 Reference Reference Reference 92 Reference Reference Reference
206 1.95 (1.37, 1.40 (1.19, 1.42 (1.19, 119 2.17 (1.52, 1.79 (1.24, 1.88 (1.29, 93 1.67 (1.15, 1.58 (1.07, 1.65 (1.12, 105 1.34 (1.08, 1.28 (1.15, 1.21 (1.07,
111 Reference Reference Reference 51 Reference Reference Reference 56 Reference Reference Reference 46 Reference Reference Reference
162 1.49 (1.18, 1.38 (1.17, 1.20 (1.07, 91 1.48 (1.07, 1.50 (1.17, 1.46 (1.09, 60 1.42 (0.92, 1.49 (0.95, 1.40 (0.88, 90 1.67 (1.09, 1.62 (1.06, 1.68 (1.09,
10.32) 7.92) 8.89) 5.33) 3.09) 3.04) 3.01) 2.76) 2.69) 4.74) 4.71) 4.93)
2.77) 2.01) 2.21) 3.09) 2.60) 2.74) 2.41) 2.33) 2.46) 1.75) 1.56) 1.61)
BMI body mass index, WC waist circumference, TG triglycerides, HDL-c high-density lipoprotein cholesterol, FPG fasting plasma glucose. Odds ratios (95% confidence interval) (all such values). b Adjusted for age, sex, BMI, smoking status, drinking stats, LDL-C, antidiabetic medication and antidyslipidemic medication. a
1.80) 1.79) 1.61) 2.25) 2.29) 2.03) 2.19) 2.33) 2.22) 2.57) 2.49) 2.61)
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DOI: 10.3109/10641963.2014.977487
not significantly correlated with prehypertension. However, age-stratified analysis showed the positive correlation between HDL-c and prehypertension in 50–59 years group. Most of the available data show that the HDL-c level in subjects with prehypertension was either lower than or not different from those with optimal BP (21,23,27,29), but there was no study on 50–59 years group. This finding was very interesting. Perhaps the correlation between HDL-c and prehypertension was related with age distribution. Further research was needed to explore the mechanism. Contrary to the HDL-c data, a positive correlation between TG and prehypertension was noted, which is consistent with most of the other studies (20,21,27,30,31). Based on these findings, we concluded that the ability of low HDL-c to predict prehypertension is less evident than that of hypertriglyceridemia, perhaps it has correlation only in special age group. The importance of hypertriglyceridemia should be stressed in middle-aged and elderly persons. In the present study, the incidence of MetS was 44.1% in the prehypertension group. Compared with those in the optimal BP group, subjects in the prehypertension group had a 3.12-fold greater risk of having MetS. They also had significantly higher OR for having abnormal WC, FPG and TG. Therefore, the importance of controlling BP should be emphasized for middle-aged and elderly persons in preventing MetS. However, we consider that our data raise some interesting questions about the role of BP even when still within its normal range. It seems that the lower the BP, the less is the chance to have MetS. Based on this observation, the next question would be ‘‘Would there be beneficial effects if we treat subjects with prehypertension to optimal BP?’’ The 2013 ESH/ESC guidelines for the management of arterial hypertension indicate that unless the necessary evidence is obtained, it is not recommended to initiate antihypertensive drug therapy at high-normal BP (32). For prehypertensive individuals, stricter control of blood glucose, blood lipid, BP and obesity is necessary. There were several limitations to our study. First, this was a cross-sectional study and the sample was not large, and the present findings were inherently limited in their ability to eliminate causal relationships between prehypertension and MetS. Secondly, part of the study population had several risk factors including diabetes and dyslipidemia, we were unable to eliminate the possible effect of underlying diseases and medications used for these diseases on our findings, but this situation is consistent with the real world. Third, this study was conducted in middle-aged and elderly people in Tianjin. Therefore, geographic differences should also be kept in mind when extrapolating our data to other populations. Given the limitations, we still believe that our results would light on the role of prehypertension in this particular population. Further studies are warranted to verify our findings. In conclusion, the present study showed that middle-aged and elderly persons with prehypertension tend to have a higher risk of having MetS, as well as abnormal WC, FPG and TG. This might prove that risks for MetS begin to increase with elevation of BP, even when it is still within the normal range. Therefore, stricter control of BP should be advocated to prevent MetS.
MS was increased in people with prehypertension
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Declaration of interest The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper. This study was supported by the Science and Technology Fund of Tianjin Health Bureau (11KG133).
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26. Okosun IS, Boltri JM, Anochie LK, et al. Racial/ethnic differences in prehypertension in American adults: population and relative attributable risks of abdominal obesity. J Hum Hypertens 2004;18: 849–55. 27. Tsai PS, Ke TL, Huang CJ, et al. Prevalence and determinants of prehypertension status in the Taiwanese general population. J Hypertens 2005;23:1355–60. 28. Hwu CM, Liou TL, Hsiao LC, et al. Prehypertension is associated with insulin resistance. QJM 2009;102:705–11. 29. Oda E, Kawai R. High-density lipoprotein cholesterol is positively associated with hypertension in apparently healthy Japanese men and women. Br J Biomed Sci 2011;68:29–33. 30. Cordero A, Laclaustra M, Leon M, et al. Prehypertension is associated with insulin resistance state and not with an initial renal function impairment. A Metabolic Syndrome in Active Subjects in Spain (MESYAS) Registry substudy. Am J Hypertens 2006;19: 189–96 (discussion 197–8). 31. Oda E, Kawai R. LDL cholesterol is associated with blood pressure in Japanese women. Diabetes Care 2009;32:e113. 32. Mancia G, Fagard R, Narkiewicz K, et al. 2013 ESH/ESC guidelines for the management of arterial hypertension: the task force for the management of arterial hypertension of the European Society of Hypertension(ESH) and of the European Society of Cardiology (ESC). J Hypertens 2013;31:1281–357.
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High prevalence of metabolic syndrome in a middle-aged and elderly population with prehypertension in Tianjin Wei Yao, Yuemin Sun, Xuechun Wang, Quan Si, Huili Chen & Zheng Wan To cite this article: Wei Yao, Yuemin Sun, Xuechun Wang, Quan Si, Huili Chen & Zheng Wan (2015) High prevalence of metabolic syndrome in a middle-aged and elderly population with prehypertension in Tianjin, Clinical and Experimental Hypertension, 37:5, 369-374, DOI: 10.3109/10641963.2014.977487 To link to this article: http://dx.doi.org/10.3109/10641963.2014.977487
Published online: 12 Dec 2014.
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Date: 05 October 2015, At: 11:33
http://informahealthcare.com/ceh ISSN: 1064-1963 (print), 1525-6006 (electronic) Clin Exp Hypertens, 2015; 37(5): 369–374 ! 2015 Informa Healthcare USA, Inc. DOI: 10.3109/10641963.2014.977487
High prevalence of metabolic syndrome in a middle-aged and elderly population with prehypertension in Tianjin Wei Yao, Yuemin Sun, Xuechun Wang, Quan Si, Huili Chen, and Zheng Wan
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Department of Cardiology, Tianjin Medical University General Hospital, Tianjin Medial University, Tianjin, China
Abstract
Keywords
Background: Prehypertension has been reported as being correlated with future cardiovascular risk and end-organ damage in middle-aged and elderly persons, and also playing an important role in metabolic syndrome (MetS). The association between prehypertension and MetS has rarely been reported among urban adults in Tianjin, China. Methods: In this cross-sectional study, a total of 1176 participants aged 40–70 years (524 males and 652 females) were enrolled after excluding participants with hypertension or treated hypertension. Participants were divided into two groups [optimal blood pressure (BP) and prehypertension] based on the classification of BP from the JNC-7. The definition of MetS was as per the International Diabetes Federation standard. An adjusted logistic regression model was used to assess relationships between prehypertension and MetS. Results: The prehypertension group had a significantly higher odds ratio (OR) than the optimal BP group for abnormal waist circumference (WC), fasting plasma glucose (FPG) and triglycerides (TG). In addition, the prehypertension group had a higher OR (3.12; 95% confidence interval 2.34–4.18) for having MetS after adjusting for potential confounders. Conclusions: The risk of having MetS was significantly associated with prehypertension in middle-aged and elderly persons in Tianjin. Stricter control of BP in this age group is warranted.
Metabolic syndrome, prehypertension, risk factor, middle-aged and elderly, primary prevention
Introduction Metabolic syndrome (MetS) is a complex medical disorder comprising five inter-related risk factors within an individual: obesity, hypertension, hypertriglyceridemia, low high-density lipoprotein cholesterol (HDL-c) and hyperglycemia (1,2). It is a growing public health issue, with approximately one-fourth of the world’s adult population having this disorder (3). In 2000, the prevalence of MetS in China was 15.1% (4). From 2007 to 2012, the prevalence of MetS in Tianjin was 19.8, 24.7, 28.8, 29.9, 33.4 and 34.4%, respectively (5). In 2008, the prevalence of abdominal obesity, elevated triglycerides (TG), reduced HDL-c, elevated blood pressure (BP) and elevated fasting plasma glucose (FPG) in Beijing was 44.6, 23.8, 33.9, 49.6 and 21.0% (6). MetS places a tremendous burden not only on the individual’s health, but also on society as a whole (7). Since the establishment of the definition of MetS, many studies have shown that it is a reliable and accurate predictor of future cardiovascular disease (CVD) and diabetes (8–10). Hypertension has been shown to be a key factor in MetS (11). The Framingham Heart Study showed that hypertension
Correspondence: Yuemin Sun, Department of Cardiology, Tianjin Medical University General Hospital, No. 154, Anshan Road, Heping District, Tianjin, 300052, P.R. China. Tel: +86-22-60362779. Fax: +8622-60362427. E-mail: [email protected]
History Received 19 July 2014 Revised 8 October 2014 Accepted 10 October 2014 Published online 11 December 2014
played an important role in MetS and has been reported to be its most commonly associated risk factor (12). In 2003, the seventh report of the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure (JNC-7) proposed a new BP category, designated ‘‘prehypertension’’, of 120–139 mmHg systolic blood pressure (SBP) or 80–89 mmHg diastolic blood pressure (DBP) (13). Some studies had indicated that cardiovascular risk and end-organ damage were already elevated in individuals with prehypertension when compared with those with a BP less than 120/80 mmHg (14). With the recent rapid economic growth and urbanization of China, the prevalence of prehypertension and MetS has significantly increased in concert with extended life expectancy, which now compares favorable with that in many other developed countries worldwide. Tianjin is a city of approximately 10.43 million inhabitants located in the northeast of the North China Plain, facing the Bohai Sea (15). Salt consumption has been shown to be higher in Tianjin because it is near the ocean, and the prevalence of smoking is high (16). These factors may contribute to the particularly high prevalence of hypertension and prehypertension in Tianjin. The present study evaluated the association between prehypertension and MetS among urban adults aged 40 years and older in Tianjin. Although several other studies have described the association between prehypertension and
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MetS, the population on the middle-aged and elderly was few (17–19). In these studies, they included only men or included only women. Through our study, we hope to provide a context for policy planners and health education programs.
Methods
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Study design and study population Study procedures were in accordance with ethical standards of the responsible committee on human experimentation of Tianjin Medical University General Hospital. Tianjin is the sixth largest city of China, located in the northeast region bordering Bohai Bay in the Pacific Ocean. From May 2011 to May 2013, residents living in the six districts of the center of Tianjin City, between the ages of 40 and 70 years, were enrolled after exclusion of participants with hypertension or treated hypertension. In the first stage, six street districts were randomly selected from each city district. In the second stage, recruitment advertisements were posted in these street districts to enroll participants. Two-hundred individuals were enrolled in each street district. All participants were free of self-reported stroke, transient ischemic attack, myocardial infarction, angina or renal failure. A total of 1176 participants including 524 males and 652 females were enrolled in the analysis. The prevalence of selfreported diabetes mellitus was 9.0% (106/1176) in the process of enrollment and 53.8% diabetic subjects received treatment with oral antidiabetic agents and/or insulin. The prevalence of self-reported dyslipidemia was 31.4% in 1176 subjects, 24.9% of whom received antidyslipidemic therapy.
Clin Exp Hypertens, 2015; 37(5): 369–374
and having SBP 5120 mmHg and DBP 580 mmHg. Prehypertension was defined as not being on antihypertensive medication and having an SBP of 120–139 mmHg or DBP of 80–89 mmHg. Body weight and height were measured by trained staff with subjects wearing light clothing and without shoes. The body mass index (BMI) was calculated as weight in kilograms divided by the square of the height in meters. The waist circumference (WC) was measured at the level of 1 cm above the umbilicus. Blood samples were drawn from the antecubital vein after a 10-h fast in the morning. FPG, total cholesterol (TC), TG, HDL-c and low-density lipoprotein cholesterol (LDL-c) were measured using a Hitachi 7180 Automatic Analyzer (Hitachi, Tokyo, Japan), with all analyses performed in accordance with the manufacturer’s recommendations. All blood samples were analyzed in the central laboratory of Tianjin Medical University General Hospital. Definition of MetS The definition of MetS was as per the International Diabetes Federation standard (1), with abdominal obesity defined as WC 90 cm (males) or 80 cm (females) plus any two of the following four abnormal metabolic components: (1) TG 1.7 mmol/l (150 mg/dl) or the use of lipid medications; (2) SBP 130 mmHg and/or DBP 85 mmHg, or the use of antihypertensive medications; (3) FPG 5.6 mmol/l (100 mg/ dl) or the use of diabetes medications; and (4) HDL-c 51.04 mmol/l (40 mg/dl) (males) or 51.29 mmol/l (50 mg/dl) (females).
Data collection and examination
Statistical analysis
An interview-based survey of hypertension was performed using a questionnaire by trained staff. Demographic data, disease history, family history of hypertension, cigarette smoking and alcohol drinking were investigated. Individuals who had smoked 5100 cigarettes during their lifetime were considered non-smoking, those who had smoked 100 cigarettes lifetime and not smoking for at least 1 year were considered past smoking, and those who had smoked 100 cigarettes lifetime and currently smoking were considered current smoking. Current alcohol drinking was defined as consumption of 1 alcoholic drink in the past month. Individuals who had never drinking during their lifetime were considered non-drinking and those who had given up drinking for at least 1 month were considered past drinking. Three BP measurements were performed by two trained doctors while the study participants were seated, using a standard mercury sphygmomanometer according to a standard protocol, after the subjects had been resting for 30 min. Standard cuff bladders (12–13 cm wide and 35 cm long) were used to measure BP, the larger and smaller bladder being available for large (arm circumference432 cm) and thin arms, respectively. The 1st and 5th Korotkoff sounds were recorded as SBP and DBP, respectively; the mean of three measurements was used in the analysis. The classification of normotensive, prehypertensive and hypertensive was based on the classification of BP from the JNC-7 (13). Optimal BP was defined as not being on antihypertensive medication
SPSS version 17.0 software (IBM, Somers, NY) was used to perform all the statistical analyses. Data were expressed as mean ± standard deviation, median with interquartile range, or percentage as appropriate. Comparisons between groups were analyzed by t test or Mann–Whitney U test for measurement data, and 2 test for enumeration data. Multiple logistic regression analysis was used to examine relationships between prehypertension and the prevalence of MetS after adjustment for covariates: age, sex, BMI, smoking status, drinking status, LDL-c, antidiabetic medication and antidyslipidemic medication. An odds ratio (OR) and 95% confidence interval were calculated. All statistical tests were two-tailed, and p values of less than 0.05 were considered statistically significant.
Results Table 1 shows the general characteristics of the study population according to baseline BP. The two groups (optimal BP and prehypertension) differed significantly in all characteristics. The mean age was 55.1 years for the optimal BP group and 57.5 years for the prehypertension group. The prehypertension group showed a significantly higher percentage of male gender, smoking, alcohol drinking, family history of hypertension, diabetes and dyslipidemia in comparison with the optimal BP group. The MetS components of WC, TG, SBP, DBP and FPG in the prehypertension group were significantly higher than those in the optimal BP group, and
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DOI: 10.3109/10641963.2014.977487
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Table 1. Baseline characteristics of study participants (n ¼ 1176). Optimal BP, n ¼ 584
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Characteristic Age (year) Sex (male, %) Family history of hypertension, (yes, %) Diabetes (yes, %) Antidiabetic medication (yes, %) Dyslipidemia (yes, %) Antidyslipidemic medication (yes, %) Alcohol drinking Current, % Past, % Non, % Smoking Current, % Past, % Non, % BMI (kg/m2) WC (cm) SBP (mmHg) DBP (mmHg) TC (mmol/l) TG, median (mmol/l) HDL-c (mmol/l) LDL-c (mmol/l) FPG, median (mmol/l)
Prehypertension, n ¼ 592
p Valuea
55.1 ± 6.8 220 (37.67) 291 (49.83) 42 (7.19) 23 (54.76) 163 (27.91) 40 (24.54)
57.5 ± 6.7 304 (51.35) 331 (56.01) 64 (10.83) 34 (53.13) 206 (34.80) 52 (25.24)
50.01 50.01 50.01 50.05 40.05 50.05 40.05
184 (31.51) 6 (1.03) 394 (67.47)
254 (42.9) 6 (1.01) 332 (56.08)
50.01 40.05 50.01
71 (12.16) 31 (5.31) 482 (82.53) 23.84 ± 3.07 83.28 ± 9.19 112.33 ± 6.71 72.76 ± 6.15 5.31 ± 1.13 1.22 (0.92, 1.70) 1.48 ± 0.37 3.18 ± 0.92 5.10 (4.70, 5.60)
99 (16.72) 50 (8.45) 443 (74.83) 25.08 ± 3.22 87.57 ± 9.57 128.63 ± 5.16 79.71 ± 6.02 5.41 ± 1.04 1.46 (1.03, 2.10) 1.42 ± 0.39 3.29 ± 0.88 5.30 (5.00, 5.70)
50.05 50.05 50.01 50.01 50.01 50.01 50.01 50.01 50.01b 50.01 50.05 50.01b
BMI body mass index, WC waist circumference, SBP systolic blood pressure, DBP diastolic blood pressure, TC total cholesterol, TG triglycerides, HDL-c high-density lipoprotein cholesterol, LDL-c low-density lipoprotein cholesterol, FPG fasting plasma glucose. a Comparisons between groups were analyzed by t test for measurement data and 2 test for enumeration data. b Comparisons between groups were analyzed by Mann–Whitney U test for TG and FPG.
Table 2. Age-standardized prevalence of MetS (n ¼ 1176).
showed the positive correlation between HDL-c and prehypertension in 50–59 years group (Table 4).
MetS, n (%) Age-group, years 40–49 (n ¼ 189) 50–59 (n ¼ 576) 60 (n ¼ 411) Total
Optimal BP 13 52 36 101
(11.1) (17.7) (20.8) (17.3)
Prehypertension 29 124 108 261
(40.8) (44.0) (45.2) (44.1)
p Valuea
50.0001
a
Comparisons between groups were analyzed by 2 test.
HDL-c was significantly lower than in the optimal BP group. The prehypertension group had an elevated mean BMI, TC and LDL-c compared with the optimal BP group. Table 2 shows the age-standardized prevalence of MetS. The prehypertension group showed a significantly higher percentage of MetS than the optimal BP group. In each age group, the percentage of MetS was significantly higher in the prehypertension group. At least on abnormal MetS component was identified in 81.9% of subjects. The prevalence of the abnormal WC, TG, HDL-c and FPG was 65.0, 32.7, 27.2 and 33.0%, respectively. The crude and adjusted relationships between prehypertension and MetS and its components are shown in Table 3. In the final multivariate models, the prehypertension group had a significantly higher OR for having MetS. Similar relationships were also observed between prehypertension and MetS components, except for HDL-c. Age-stratified analysis
Discussion As the health care system becomes increasingly effective, aging is now a significant issue in China, as in many other developed countries. Therefore, health promotion and disease prevention in the middle-aged and elderly population are important policies for the Department of Health. The purpose of the present study was to determine whether participants with prehypertension would be at higher risk of having MetS. Although many studies have already explored this type of relationship in participants with prehypertension (20–23), very few studies included urban participants from Tianjin. In this study, we demonstrated that even when the BP is within the normal range, it will cause increasing comorbidity concomitant with the rise in BP. Multiple logistic regression analysis was used to evaluate the relationships between prehypertension and MetS, and its components. We adjusted for a number of potentially confounding factors in our analyses. Studies have shown that age and sex are simultaneously related to the incidence of MetS (24), and BMI is an important risk factor that can cause a variety of adverse health effects (25); therefore, we first adjusted for age, sex and BMI. However, adjustment for these factors did not significantly affect the relationship between the prehypertension and MetS, leading us to consider that the direct relationship between prehypertension and MetS was
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independent of age, sex and BMI. We subsequently adjusted for other factors including smoking, drinking status, LDL-c and history of antidiabetic medication and antidyslipidemic medication. However, these adjustments also did not affect the positive relationship between prehypertension and MetS. Table 3. Adjusted relationships between prehypertension and metabolic syndrome and its components.
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Prehypertension
Number with MetS Crude Age-, sex- and BMI-adjusted Multiple adjustedb Mets components Number with elevated WC Crude Age-, sex- and BMI-adjusted Multiple adjustedb Number with elevated TG Crude Age-, sex- and BMI-adjusted Multiple adjustedb Number with reduced HDL-c Crude Age-, sex- and BMI-adjusted Multiple adjustedb Number with elevated FPG Crude Age-, sex- and BMI-adjusted Multiple adjustedb
No, (n ¼ 584)
Yes, (n ¼ 592)
101 Reference Reference Reference
251 3.52 (2.69, 4.61)a 3.07 (2.30, 4.09) 3.12 (2.34, 4.18)
337 Reference Reference Reference 147 Reference Reference Reference 150 Reference Reference Reference 165 Reference Reference Reference
427 1.90 (1.49, 1.53 (1.13, 1.51 (1.11, 238 1.99 (1.56, 1.73 (1.33, 1.72 (1.32, 176 1.22 (0.95, 1.13 (0.86, 1.19 (0.90, 223 1.53 (1.20, 1.40 (1.09, 1.39 (1.08,
2.42) 2.08) 2.06) 2.56) 2.24) 2.24) 1.58) 1.48) 1.56) 1.96) 1.81) 1.80)
BMI body mass index, WC waist circumference, TG triglycerides, HDL-c high-density lipoprotein cholesterol, FPG fasting plasma glucose. a Odds ratios (95% confidence interval) (all such values). b Adjusted for age, sex, BMI, smoking status, drinking stats, LDL-C, antidiabetic medication and antidyslipidemic medication.
In our study, the prevalence of abnormal WC was 65%, higher than that of any other MetS components. Elevated WC was positively correlated with prehypertension. Similar findings can also be found in many other reports. In a cohort of 5050 Chinese men aged from 35 to 74 years, individuals with central obesity and overweight had a significantly higher prevalence of prehypertension than those of normal weight (21). Okosun et al. revealed that abdominal obesity was associated with an increased risk of prehypertension in Americans (26), independent of age, FPG, TC, exercise and current smoking. Our finding further confirmed that participants with prehypertension had a high prevalence of elevated WC. As a result, the importance of controlling obesity should be emphasized for middle-aged and elderly persons in order to prevent hypertension. Numerous studies have shown that FPG is higher in prehypertension and hypertension (21–23,27,28). Subjects with hypertension and prehypertension are more prone to developing diabetes than persons with optimal BP. Similar results were also found in our present study. This is not surprising because insulin resistance (IR) is considered to be the core of MetS (1) and high BP is related to IR. Our data suggested that participants in the prehypertension group had a 1.39-fold increased risk of having elevated FPG than those in the optimal BP group. Therefore, the conclusion could be drawn that middle-aged and elderly persons with prehypertension are at higher risk of developing diabetes in the future. Dyslipidemia also plays a major role in the development of MetS, CVD and diabetes. Our data showed that the HDL-c level was lower in the prehypertension group, but multiple logistic regression analysis showed that HDL-c was
Table 4. Aged-stratified analysis of the relationship between prehypertension and metabolic syndrome and its components.
Age-stratified analysis Number with MetS Crude Age-, sex- and BMI-adjusted Multiple adjustedb Mets components Number with elevated WC Crude Age-, sex- and BMI-adjusted Multiple adjustedb Number with elevated TG Crude Age-, sex- and BMI-adjusted Multiple adjustedb Number with reduced HDL-c Crude Age-, sex- and BMI-adjusted Multiple adjustedb Number with elevated FPG Crude Age-, sex- and BMI-adjusted Multiple adjustedb
40–49 years group (n ¼ 189)
50–59 years group (n ¼ 576)
60 years group (n ¼ 411)
Prehypertension
Prehypertension
Prehypertension
No
Yes
No
Yes
No
Yes
13 Reference Reference Reference
29 5.39 (2.56, 11.35)a 3.35 (1.48, 7.54) 3.45 (1.50, 7.96)
52 Reference Reference Reference
124 3.65 (2.50, 5.35) 3.11 (2.07, 4.67) 3.27 (2.17, 4.95)
36 Reference Reference Reference
98 2.66 (1.70, 4.17) 2.56 (1.67, 4.06) 2.98 (1.83, 4.86)
55 Reference Reference Reference 22 Reference Reference Reference 23 Reference Reference Reference 24 Reference Reference Reference
59 5.11 (2.54, 3.43 (1.49, 3.76 (1.59, 28 2.75 (1.42, 1.71 (1.18, 1.70 (1.09, 27 1.57 (0.81, 1.29 (0.61, 1.25 (0.58, 28 2.47 (1.28, 2.26 (1.08, 2.34 (1.11,
171 Reference Reference Reference 74 Reference Reference Reference 67 Reference Reference Reference 92 Reference Reference Reference
206 1.95 (1.37, 1.40 (1.19, 1.42 (1.19, 119 2.17 (1.52, 1.79 (1.24, 1.88 (1.29, 93 1.67 (1.15, 1.58 (1.07, 1.65 (1.12, 105 1.34 (1.08, 1.28 (1.15, 1.21 (1.07,
111 Reference Reference Reference 51 Reference Reference Reference 56 Reference Reference Reference 46 Reference Reference Reference
162 1.49 (1.18, 1.38 (1.17, 1.20 (1.07, 91 1.48 (1.07, 1.50 (1.17, 1.46 (1.09, 60 1.42 (0.92, 1.49 (0.95, 1.40 (0.88, 90 1.67 (1.09, 1.62 (1.06, 1.68 (1.09,
10.32) 7.92) 8.89) 5.33) 3.09) 3.04) 3.01) 2.76) 2.69) 4.74) 4.71) 4.93)
2.77) 2.01) 2.21) 3.09) 2.60) 2.74) 2.41) 2.33) 2.46) 1.75) 1.56) 1.61)
BMI body mass index, WC waist circumference, TG triglycerides, HDL-c high-density lipoprotein cholesterol, FPG fasting plasma glucose. Odds ratios (95% confidence interval) (all such values). b Adjusted for age, sex, BMI, smoking status, drinking stats, LDL-C, antidiabetic medication and antidyslipidemic medication. a
1.80) 1.79) 1.61) 2.25) 2.29) 2.03) 2.19) 2.33) 2.22) 2.57) 2.49) 2.61)
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DOI: 10.3109/10641963.2014.977487
not significantly correlated with prehypertension. However, age-stratified analysis showed the positive correlation between HDL-c and prehypertension in 50–59 years group. Most of the available data show that the HDL-c level in subjects with prehypertension was either lower than or not different from those with optimal BP (21,23,27,29), but there was no study on 50–59 years group. This finding was very interesting. Perhaps the correlation between HDL-c and prehypertension was related with age distribution. Further research was needed to explore the mechanism. Contrary to the HDL-c data, a positive correlation between TG and prehypertension was noted, which is consistent with most of the other studies (20,21,27,30,31). Based on these findings, we concluded that the ability of low HDL-c to predict prehypertension is less evident than that of hypertriglyceridemia, perhaps it has correlation only in special age group. The importance of hypertriglyceridemia should be stressed in middle-aged and elderly persons. In the present study, the incidence of MetS was 44.1% in the prehypertension group. Compared with those in the optimal BP group, subjects in the prehypertension group had a 3.12-fold greater risk of having MetS. They also had significantly higher OR for having abnormal WC, FPG and TG. Therefore, the importance of controlling BP should be emphasized for middle-aged and elderly persons in preventing MetS. However, we consider that our data raise some interesting questions about the role of BP even when still within its normal range. It seems that the lower the BP, the less is the chance to have MetS. Based on this observation, the next question would be ‘‘Would there be beneficial effects if we treat subjects with prehypertension to optimal BP?’’ The 2013 ESH/ESC guidelines for the management of arterial hypertension indicate that unless the necessary evidence is obtained, it is not recommended to initiate antihypertensive drug therapy at high-normal BP (32). For prehypertensive individuals, stricter control of blood glucose, blood lipid, BP and obesity is necessary. There were several limitations to our study. First, this was a cross-sectional study and the sample was not large, and the present findings were inherently limited in their ability to eliminate causal relationships between prehypertension and MetS. Secondly, part of the study population had several risk factors including diabetes and dyslipidemia, we were unable to eliminate the possible effect of underlying diseases and medications used for these diseases on our findings, but this situation is consistent with the real world. Third, this study was conducted in middle-aged and elderly people in Tianjin. Therefore, geographic differences should also be kept in mind when extrapolating our data to other populations. Given the limitations, we still believe that our results would light on the role of prehypertension in this particular population. Further studies are warranted to verify our findings. In conclusion, the present study showed that middle-aged and elderly persons with prehypertension tend to have a higher risk of having MetS, as well as abnormal WC, FPG and TG. This might prove that risks for MetS begin to increase with elevation of BP, even when it is still within the normal range. Therefore, stricter control of BP should be advocated to prevent MetS.
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Declaration of interest The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper. This study was supported by the Science and Technology Fund of Tianjin Health Bureau (11KG133).
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