Childhood Environment Influences Adrenarcheal Timing among First-Generation Bangladeshi Migrant Girls to the UK

Abstract

Background: Adrenarche is a key early life event that marks middle childhood at approximately 7 years of age. Earlier work with British-Bangladeshi migrant women suggested that environmental conditions experienced before adrenarche influence adult reproductive function. We therefore investigated whether Bangladeshi children who migrate to the United Kingdom (UK) reach adrenarche earlier than non-migrants in Bangladesh or the United Kingdom. Methods and Findings: Healthy girls, aged 5–16 years, were recruited from schools in Sylhet, Bangladesh and London, England comprising four groups: Sylhetis (n = 165), first-generation migrants to the United Kingdom (n = 42), second-generation girls (n = 162), and British girls of European origin (n = 50). Anthropometric measurements were collected together with questionnaire data for migration and socioeconomic characteristics. Saliva samples were assayed for dehydroepiandrosterone (DHEAS) using enzyme-linked immunosorbent assays. Multiple linear regressions tested for group differences in anthropometric and socioeconomic variables and DHEAS levels. Median ages at adrenarche (DHEAS>400 pg/ml) were estimated using Weibull regression models for parametric survival analysis. Hazard ratios for reaching adrenarche earlier and 95% confidence intervals (CI), both unadjusted and adjusted for anthropometric variables, were estimated from the survival analyses. First-generation migrants had a median age at adrenarche (5.3 years) that was significantly earlier than Sylheti (7.2), second-generation (7.4), and European (7.1) girls. In univariate analyses, first-generation girls reached adrenarche significantly earlier than Sylhetis [HR (CI): 2.8 (1.4–5.5]. In multivariate models, first generation girls still reached adrenarche earlier than Sylhetis after adjusting for height [HR(CI): 1.9 (0.9–4.1)] and weight [HR(CI):1.7 (0.8–3.8)], but these results were attenuated. Conclusions: We suggest that rapid catch-up growth experienced by first generation girls during early childhood may explain their advanced adrenarche. The environmental conditions leading to an earlier adrenarche, as well as the health implications of this early transition, merit further exploration.