Body mass index, waist circumference and body fat are positively correlated with hair cortisol in children: A systematic review and meta-analysis.

The current body of research lacks a meta-analysis of the relationship between hair cortisol concentration (HCC) and anthropometry in children. Therefore, this systematic review and meta-analysis was conducted to examine this relationship and explore possible moderators between HCC and body mass index (BMI/BMI z-score). Eleven databases were searched: CINAHL, Cochrane, Embase, PsycEXTRA, Psychology and Behavioral Sciences, PsycINFO, PubMed, Scopus, Social Sciences Full Text, Sociological Abstracts and Web of Sciences. Random-effects models and exploratory moderator analyses with mixed-effects models were performed using the Comprehensive Meta-Analysis software. The meta-analysis showed small positive correlations between HCC and BMI (r = 0.08, 95% confidence interval [CI]: 0.02, 0.14, n = 18, p = .009), BMI z-score (r = 0.10, 95% CI: 0.03, 0.16, n = 12, p = .003), waist circumference (r = 0.10, 95% CI: 0.04, 0.17, n = 10, p = .001) and body fat including fat mass index (r = 0.06, 95% CI: 0.02, 0.11, n = 3, p = .005). The relationship between HCC and BMI/BMI z-score was significantly moderated by children's sex. Results from this meta-analysis provide initial objective support for a small positive relationship between HCC and anthropometric factors.