Annals of Epidemiology 25 (2015) 90e95
Contents lists available at ScienceDirect
Annals of Epidemiology journal homepage: www.annalsofepidemiology.org
Original article
Hair cortisol in relation to sociodemographic and lifestyle characteristics in a multiethnic US sample Adaeze C. Wosu MPH a, *, Bizu Gelaye PhD a, Unnur Valdimarsdóttir PhD a, b, Clemens Kirschbaum PhD c, Tobias Stalder PhD c, Alexandra E. Shields PhD d, Michelle A. Williams ScD a a
Department of Epidemiology, Harvard School of Public Health, Boston, MA Center of Public Health Sciences, Faculty of Medicine, University of Iceland, Reykjavik, Iceland Department of Psychology, Technical University of Dresden, Dresden, Germany d Department of Medicine, Harvard Medical School, Harvard/Massachusetts General Hospital Center for Genomics, Vulnerable Populations and Health Disparities, Mongan Institute for Health Policy, Boston, MA b c
a r t i c l e i n f o
a b s t r a c t
Article history: Received 1 May 2014 Accepted 23 November 2014 Available online 28 November 2014
Purpose: We investigated the feasibility of obtaining hair samples from men and women at communitybased barbershops and hair salons for analysis of cortisol and assessed sociodemographic and lifestyle correlates of hair cortisol concentrations (HCCs). A total of 102 participants completed the study. Methods: Research staff interviewed participants using a structured questionnaire, and samples of hair were collected. HCCs were determined using liquid chromatography-tandem mass spectrometry. Ageand sex-adjusted linear regression models were used to evaluate the association of HCC with covariates. Results:: Analyses by race/ethnicity showed highest median HCC in blacks (12.5 [6.9e29.3]) pg/mg) followed by Hispanics (10.7 [5.8e14.9] pg/mg), whites (5.0 [3.8e10.8] pg/mg), and other participants (4.2 [3.3e15.7] pg/mg), P < .01. Current smokers had significantly higher median HCC (11.7 [8.8e18.9] pg/mg) compared with former smokers (4.6 [3.5e14.6] pg/mg) and those who had never smoked (6.9 [4.7e12.8] pg/mg), P ¼ .04. After adjustment for age and sex, geometric mean HCC was 0.72 pg/mg lower in dyed hair compared with hair that was not dyed (b ¼ 0.72, standard error ¼ 0.30, 95% confidence interval, 1.29 to 0.15, P ¼ .02). Conclusions: HCC can be assessed in community-based studies. Future HCC studies should consider cosmetic hair treatment, cigarette smoking, and the potential role of psychosocial stressors in the association between race/ethnicity and HCC. Ó 2015 Elsevier Inc. All rights reserved.
Keywords: Correlates Race Ethnicity Chronic stress Biomarker Community
Introduction In recent years, the incorporation of hair cortisol as a biomarker of chronic stress in epidemiologic studies has gained increased traction. Previously, cortisol was primarily measured in saliva, blood, and urine. However, cortisol measured in these tissues only reflect acute synthesis and release; and collection of samples, particularly blood, can be invasive. In contrast, hair grows over lengthy periods of time, and hair cortisol concentrations (HCCs) are thus assumed to reflect integrated cortisol levels released over
The authors report no conflict of interest. The authors are responsible for the content and writing of the article. * Corresponding author. Department of Epidemiology, Harvard School of Public Health, 677 Huntington Avenue, Kresge, Room 500, Boston, MA 02115. Tel.: þ1 617432-0012; fax: þ1 617-566-7805. E-mail address: [email protected] (A.C. Wosu). http://dx.doi.org/10.1016/j.annepidem.2014.11.022 1047-2797/Ó 2015 Elsevier Inc. All rights reserved.
several months [1]. Thus, the noninvasive method of hair sampling overcomes some of the important limitations of traditional samples with regard to assessing long-term cortisol release. Investigators have examined the relationship between HCC and measures of stress, putative stressors, and stress-related conditions. Associations have been observed between elevated HCC and sociodemographic factors including unemployment [2] and low parental education level [3]. However, most of the earlier studies have focused on European populations; relatively little is known about the correlates of HCC in multiethnic populations, particularly among blacks and Hispanics in the United States. Given this gap in the literature, we conducted a pilot study to assess the feasibility of collecting hair samples from adults in community-based barbershops and hair salons for analysis of HCC; and to evaluate associations of HCC with various sociodemographic and lifestyle characteristics, including hair washing frequency and other hairrelated factors.
A.C. Wosu et al. / Annals of Epidemiology 25 (2015) 90e95
Methods Study design, setting, and sample This cross-sectional study was conducted between April and June 2013 at five ethnically diverse community-based barbershops and hair salons in the Greater Boston area of Massachusetts. A total of 102 participants (41 men and 61 women) who were clients at these establishments were recruited into the study as described in the following. Recruitment Potential participants were approached by trained research staff in waiting areas of the establishments and were informed about the study purpose and procedures. Individuals with two or more centimeters of hair in the posterior vertex region of the head were eligible to participate. Individuals were ineligible if they were younger than 18 years of age or did not understand and speak English. Eligible individuals who expressed interest in participating in the study were led to a private room where informed consent and other study procedures were carried out. The procedures used in this study were in agreement with the protocols approved by the Institutional Review Board of the Harvard School of Public Health Office of Human Research Administration, Boston, MA. All participants provided written informed consent. At the end of the study, participants were given compensation worth $20 that could be used toward services at the barbershop or hair salon. Data collection and variables Using a structured questionnaire, research staff interviewed participants and collected information on sociodemographic and lifestyle characteristics. Interviews were 20 to 25 minutes long. Sociodemographic information included age (years), sex (male and female), self-identified race and/or ethnicity (white, black, Hispanic, other, that is, multiracial or self-identified race/ethnicity other than white, black or Hispanic), years of education (0e12, 13e16, 17), and household income ($25,000; $25,001e$50,000; $50,001e$75,000; and >$75,000). Lifestyle factors included quantity of alcohol consumed per drinking occasion (none, moderate [i.e., 4 drinks in 1 day for men and 3 drinks on 1 day for women], heavy [i.e., >4 drinks in 1 day for males and >3 drinks in 1 day for women]), cigarette smoking status (never, former, and current), and participation in regular physical activity, that is ride a bicycle, participate in sports, jog, lift weights, swim, walk, or participate in any other exercise activities on a regular basis (no, yes). Hair-related factors were characterized as follows: natural hair color (black, dark brown, light brown, and red/auburn/blond), natural hair texture (straight, wavy, loosely coiled, and tightly coiled), frequency of hair washing (number of days on which hair was washed per week), use of hair dye (no, yes), and use of hair relaxers/perms (no, yes). Hair sample collection and cortisol measurements Approximately 100 strands of hair were sampled from the posterior vertex region. Hair from this region is the standard for hair analysis and has been shown to have higher cortisol content compared with hair from other regions [4]. An average hair growth rate of 1 cm/month was assumed for the present study [5]; however, slower hair growth rate has been observed for persons of African descent compared with whites [6]. Based on a mean hair growth rate of 256 mm/day observed for African participants in a previous study, we estimated a 0.80-cm monthly hair growth rate for black participants [6]. We thus analyzed the proximal 1.6-cm
91
segment of each sample for black participants, and the proximal 2-cm segment for all other participants to assess cortisol accumulation over the past 2 months. Hair cortisol extraction procedures were similar to methods detailed by Stalder et al. [7] with some changes. Briefly, samples were washed in 2.5 mL isopropanol for 3 minutes and dried for at least 12 hours, after which 7.5 0.5 mg of whole nonpulverized hair was weighed out. Centrifugation was omitted because whole hair was used. Samples were incubated in 1.8 mL methanol for 18 hours at room temperature and then 1.6 mL of clear supernatant was transferred into a glass vial. Subsequently, methanol was evaporated at 55 C under a steady stream of nitrogen. The residue was resuspended using 150 mL distilled water plus 20 mL of internal standard (cortisol-d4), 150 mL of which was used for liquid chromatography-tandem mass spectrometry analysis. Intra-assay and inter-assay coefficients of variance are between 3.7% and 9.1% [8]. Two participants with especially high HCC (>400 pg/mg) were excluded from data analysis, leaving a final analyzed sample of 100. Statistical analysis We first examined the frequency distributions of sociodemographic, lifestyle, and hair-related characteristics and summarized them by sex, using counts and percentages for categorical variables and medians and interquartile ranges for nonnormally distributed continuous variables. We used c2 or Fisher’s exact tests to examine group differences for categorical variables, and the ManneWhitney U test or the KruskaleWallis test for assessing differences between median HCC for variables with two or more groups. We estimated correlation coefficients and used multivariate linear regression procedures (adjusted for age and sex) to examine the relation between HCC and covariates of interest. The distribution of HCC was positively skewed; thus, the values were transformed using natural logarithms in the regression analyses. Thus, the presented means of the regression analyses were geometric means. Statistical analyses were completed using SAS software, Version 9.2 (SAS Institute, Cary, NC). All reported P values are two sided and considered statistically significant at a ¼ 0.05. Results The sociodemographic, lifestyle, and hair-related characteristics of participants are summarized in Table 1. Median age of participants was 32 years (range: 18e72). The majority of participants were women, with at least 12 years of education and with household income of less than $75,000. The sample was racially diverse, with participants self-identifying as white (35%), black (31%), Hispanic (23%), and other racial/ethnic categories (11%). Use of hair dye was reported by 29% of participants (5.1% of men and 44.3% of women), whereas only 10% of participants reported using relaxers or perms (0% men, 16.4% women). Table 2 summarizes median HCC distribution according to demographic, lifestyle, and hair-related characteristics. The median HCC for the entire sample was 8.3 (interquartile range, 4.3e14.5) pg/mg. There was no statistically significant difference in median HCC between women (9.4 [5.0e14.4] pg/mg) and men (5.9 [3.8e14.6] pg/mg, P ¼ .29). Median HCC was highest in blacks (12.5 [6.9e29.3] pg/mg) followed by Hispanics (10.7 [5.8e14.9] pg/mg), whites (5.0 [3.8e10.8] pg/mg), and other participants (4.2 [3.3e15.7] pg/mg), P < .01 (Fig. 1A). Stratified analyses showed statistically significantly higher median HCC in Hispanic men (15.0 [10.7e38.4] pg/mg) compared with white men (5.0 [3.7e8.1] pg/ mg), P < .01. Among women, median HCC was as follows: blacks (11.2 [6.8e26.4] pg/mg), Hispanics (9.4 [5.3e12.2] pg/mg), and whites (6.1 [4.1e12.2] pg/mg), P ¼ .10. Participants with low
92
A.C. Wosu et al. / Annals of Epidemiology 25 (2015) 90e95
Table 1 Sociodemographic, lifestyle, and hair-related characteristics of study participants Characteristics
Age (y) (median, interquartile range) Age group (y) 18e25 26e40 41 Race/ethnicity White Black Hispanic Other Annual household income $25,000 $25,001e$50,000 $50,001e$75,000 $75,000 Years of education 0e12 13e16 17 Cigarette smoking status Never Former Current Quantity of alcohol consumed per drinking occasion* None Low/moderate Heavy Participation in regular physical activity No Yes Use of hair dye No Yes Use of hair relaxers/perms No Yes Number of days on which participant washes hair per week (median, interquartile range)
All (N ¼ 100)
Men (N ¼ 39)
Women (N ¼ 61)
n
%
%
32 (25e43)
31 (26e43)
32 (24e43)
P value
.90
28 41 31
23.1 48.7 28.2
31.1 36.1 32.8
.44 d d
35 31 23 11
51.3 7.7 23.1 17.9
24.6 45.9 23.0 6.5
Contents lists available at ScienceDirect
Annals of Epidemiology journal homepage: www.annalsofepidemiology.org
Original article
Hair cortisol in relation to sociodemographic and lifestyle characteristics in a multiethnic US sample Adaeze C. Wosu MPH a, *, Bizu Gelaye PhD a, Unnur Valdimarsdóttir PhD a, b, Clemens Kirschbaum PhD c, Tobias Stalder PhD c, Alexandra E. Shields PhD d, Michelle A. Williams ScD a a
Department of Epidemiology, Harvard School of Public Health, Boston, MA Center of Public Health Sciences, Faculty of Medicine, University of Iceland, Reykjavik, Iceland Department of Psychology, Technical University of Dresden, Dresden, Germany d Department of Medicine, Harvard Medical School, Harvard/Massachusetts General Hospital Center for Genomics, Vulnerable Populations and Health Disparities, Mongan Institute for Health Policy, Boston, MA b c
a r t i c l e i n f o
a b s t r a c t
Article history: Received 1 May 2014 Accepted 23 November 2014 Available online 28 November 2014
Purpose: We investigated the feasibility of obtaining hair samples from men and women at communitybased barbershops and hair salons for analysis of cortisol and assessed sociodemographic and lifestyle correlates of hair cortisol concentrations (HCCs). A total of 102 participants completed the study. Methods: Research staff interviewed participants using a structured questionnaire, and samples of hair were collected. HCCs were determined using liquid chromatography-tandem mass spectrometry. Ageand sex-adjusted linear regression models were used to evaluate the association of HCC with covariates. Results:: Analyses by race/ethnicity showed highest median HCC in blacks (12.5 [6.9e29.3]) pg/mg) followed by Hispanics (10.7 [5.8e14.9] pg/mg), whites (5.0 [3.8e10.8] pg/mg), and other participants (4.2 [3.3e15.7] pg/mg), P < .01. Current smokers had significantly higher median HCC (11.7 [8.8e18.9] pg/mg) compared with former smokers (4.6 [3.5e14.6] pg/mg) and those who had never smoked (6.9 [4.7e12.8] pg/mg), P ¼ .04. After adjustment for age and sex, geometric mean HCC was 0.72 pg/mg lower in dyed hair compared with hair that was not dyed (b ¼ 0.72, standard error ¼ 0.30, 95% confidence interval, 1.29 to 0.15, P ¼ .02). Conclusions: HCC can be assessed in community-based studies. Future HCC studies should consider cosmetic hair treatment, cigarette smoking, and the potential role of psychosocial stressors in the association between race/ethnicity and HCC. Ó 2015 Elsevier Inc. All rights reserved.
Keywords: Correlates Race Ethnicity Chronic stress Biomarker Community
Introduction In recent years, the incorporation of hair cortisol as a biomarker of chronic stress in epidemiologic studies has gained increased traction. Previously, cortisol was primarily measured in saliva, blood, and urine. However, cortisol measured in these tissues only reflect acute synthesis and release; and collection of samples, particularly blood, can be invasive. In contrast, hair grows over lengthy periods of time, and hair cortisol concentrations (HCCs) are thus assumed to reflect integrated cortisol levels released over
The authors report no conflict of interest. The authors are responsible for the content and writing of the article. * Corresponding author. Department of Epidemiology, Harvard School of Public Health, 677 Huntington Avenue, Kresge, Room 500, Boston, MA 02115. Tel.: þ1 617432-0012; fax: þ1 617-566-7805. E-mail address: [email protected] (A.C. Wosu). http://dx.doi.org/10.1016/j.annepidem.2014.11.022 1047-2797/Ó 2015 Elsevier Inc. All rights reserved.
several months [1]. Thus, the noninvasive method of hair sampling overcomes some of the important limitations of traditional samples with regard to assessing long-term cortisol release. Investigators have examined the relationship between HCC and measures of stress, putative stressors, and stress-related conditions. Associations have been observed between elevated HCC and sociodemographic factors including unemployment [2] and low parental education level [3]. However, most of the earlier studies have focused on European populations; relatively little is known about the correlates of HCC in multiethnic populations, particularly among blacks and Hispanics in the United States. Given this gap in the literature, we conducted a pilot study to assess the feasibility of collecting hair samples from adults in community-based barbershops and hair salons for analysis of HCC; and to evaluate associations of HCC with various sociodemographic and lifestyle characteristics, including hair washing frequency and other hairrelated factors.
A.C. Wosu et al. / Annals of Epidemiology 25 (2015) 90e95
Methods Study design, setting, and sample This cross-sectional study was conducted between April and June 2013 at five ethnically diverse community-based barbershops and hair salons in the Greater Boston area of Massachusetts. A total of 102 participants (41 men and 61 women) who were clients at these establishments were recruited into the study as described in the following. Recruitment Potential participants were approached by trained research staff in waiting areas of the establishments and were informed about the study purpose and procedures. Individuals with two or more centimeters of hair in the posterior vertex region of the head were eligible to participate. Individuals were ineligible if they were younger than 18 years of age or did not understand and speak English. Eligible individuals who expressed interest in participating in the study were led to a private room where informed consent and other study procedures were carried out. The procedures used in this study were in agreement with the protocols approved by the Institutional Review Board of the Harvard School of Public Health Office of Human Research Administration, Boston, MA. All participants provided written informed consent. At the end of the study, participants were given compensation worth $20 that could be used toward services at the barbershop or hair salon. Data collection and variables Using a structured questionnaire, research staff interviewed participants and collected information on sociodemographic and lifestyle characteristics. Interviews were 20 to 25 minutes long. Sociodemographic information included age (years), sex (male and female), self-identified race and/or ethnicity (white, black, Hispanic, other, that is, multiracial or self-identified race/ethnicity other than white, black or Hispanic), years of education (0e12, 13e16, 17), and household income ($25,000; $25,001e$50,000; $50,001e$75,000; and >$75,000). Lifestyle factors included quantity of alcohol consumed per drinking occasion (none, moderate [i.e., 4 drinks in 1 day for men and 3 drinks on 1 day for women], heavy [i.e., >4 drinks in 1 day for males and >3 drinks in 1 day for women]), cigarette smoking status (never, former, and current), and participation in regular physical activity, that is ride a bicycle, participate in sports, jog, lift weights, swim, walk, or participate in any other exercise activities on a regular basis (no, yes). Hair-related factors were characterized as follows: natural hair color (black, dark brown, light brown, and red/auburn/blond), natural hair texture (straight, wavy, loosely coiled, and tightly coiled), frequency of hair washing (number of days on which hair was washed per week), use of hair dye (no, yes), and use of hair relaxers/perms (no, yes). Hair sample collection and cortisol measurements Approximately 100 strands of hair were sampled from the posterior vertex region. Hair from this region is the standard for hair analysis and has been shown to have higher cortisol content compared with hair from other regions [4]. An average hair growth rate of 1 cm/month was assumed for the present study [5]; however, slower hair growth rate has been observed for persons of African descent compared with whites [6]. Based on a mean hair growth rate of 256 mm/day observed for African participants in a previous study, we estimated a 0.80-cm monthly hair growth rate for black participants [6]. We thus analyzed the proximal 1.6-cm
91
segment of each sample for black participants, and the proximal 2-cm segment for all other participants to assess cortisol accumulation over the past 2 months. Hair cortisol extraction procedures were similar to methods detailed by Stalder et al. [7] with some changes. Briefly, samples were washed in 2.5 mL isopropanol for 3 minutes and dried for at least 12 hours, after which 7.5 0.5 mg of whole nonpulverized hair was weighed out. Centrifugation was omitted because whole hair was used. Samples were incubated in 1.8 mL methanol for 18 hours at room temperature and then 1.6 mL of clear supernatant was transferred into a glass vial. Subsequently, methanol was evaporated at 55 C under a steady stream of nitrogen. The residue was resuspended using 150 mL distilled water plus 20 mL of internal standard (cortisol-d4), 150 mL of which was used for liquid chromatography-tandem mass spectrometry analysis. Intra-assay and inter-assay coefficients of variance are between 3.7% and 9.1% [8]. Two participants with especially high HCC (>400 pg/mg) were excluded from data analysis, leaving a final analyzed sample of 100. Statistical analysis We first examined the frequency distributions of sociodemographic, lifestyle, and hair-related characteristics and summarized them by sex, using counts and percentages for categorical variables and medians and interquartile ranges for nonnormally distributed continuous variables. We used c2 or Fisher’s exact tests to examine group differences for categorical variables, and the ManneWhitney U test or the KruskaleWallis test for assessing differences between median HCC for variables with two or more groups. We estimated correlation coefficients and used multivariate linear regression procedures (adjusted for age and sex) to examine the relation between HCC and covariates of interest. The distribution of HCC was positively skewed; thus, the values were transformed using natural logarithms in the regression analyses. Thus, the presented means of the regression analyses were geometric means. Statistical analyses were completed using SAS software, Version 9.2 (SAS Institute, Cary, NC). All reported P values are two sided and considered statistically significant at a ¼ 0.05. Results The sociodemographic, lifestyle, and hair-related characteristics of participants are summarized in Table 1. Median age of participants was 32 years (range: 18e72). The majority of participants were women, with at least 12 years of education and with household income of less than $75,000. The sample was racially diverse, with participants self-identifying as white (35%), black (31%), Hispanic (23%), and other racial/ethnic categories (11%). Use of hair dye was reported by 29% of participants (5.1% of men and 44.3% of women), whereas only 10% of participants reported using relaxers or perms (0% men, 16.4% women). Table 2 summarizes median HCC distribution according to demographic, lifestyle, and hair-related characteristics. The median HCC for the entire sample was 8.3 (interquartile range, 4.3e14.5) pg/mg. There was no statistically significant difference in median HCC between women (9.4 [5.0e14.4] pg/mg) and men (5.9 [3.8e14.6] pg/mg, P ¼ .29). Median HCC was highest in blacks (12.5 [6.9e29.3] pg/mg) followed by Hispanics (10.7 [5.8e14.9] pg/mg), whites (5.0 [3.8e10.8] pg/mg), and other participants (4.2 [3.3e15.7] pg/mg), P < .01 (Fig. 1A). Stratified analyses showed statistically significantly higher median HCC in Hispanic men (15.0 [10.7e38.4] pg/mg) compared with white men (5.0 [3.7e8.1] pg/ mg), P < .01. Among women, median HCC was as follows: blacks (11.2 [6.8e26.4] pg/mg), Hispanics (9.4 [5.3e12.2] pg/mg), and whites (6.1 [4.1e12.2] pg/mg), P ¼ .10. Participants with low
92
A.C. Wosu et al. / Annals of Epidemiology 25 (2015) 90e95
Table 1 Sociodemographic, lifestyle, and hair-related characteristics of study participants Characteristics
Age (y) (median, interquartile range) Age group (y) 18e25 26e40 41 Race/ethnicity White Black Hispanic Other Annual household income $25,000 $25,001e$50,000 $50,001e$75,000 $75,000 Years of education 0e12 13e16 17 Cigarette smoking status Never Former Current Quantity of alcohol consumed per drinking occasion* None Low/moderate Heavy Participation in regular physical activity No Yes Use of hair dye No Yes Use of hair relaxers/perms No Yes Number of days on which participant washes hair per week (median, interquartile range)
All (N ¼ 100)
Men (N ¼ 39)
Women (N ¼ 61)
n
%
%
32 (25e43)
31 (26e43)
32 (24e43)
P value
.90
28 41 31
23.1 48.7 28.2
31.1 36.1 32.8
.44 d d
35 31 23 11
51.3 7.7 23.1 17.9
24.6 45.9 23.0 6.5
