MRC Integrative Epidemiology Unit (IEU) Seminar Series

Title: The Puberty Cohort nested within the Danish National Birth Cohort and first results

Abstract: 

Title of the cohort: The Puberty Cohort in the Danish National Birth Cohort (DNBC)

Cohort purpose: The DNBC Puberty Cohort was set up to examine potential early life causes and consequences of altered timing of pubertal development.

Cohort Basics: A sample of 22,439 singletons born during 2000-2003 into the DNBC was invited to participate in the data collection on pubertal status from 2012. Of these, 15,819 (70 %, 7,696 boys and 8,123 girls) have minimum one measure on pubertal development. Mothers were requested to complete four baseline computer-assisted telephone interviews around gestational week 17 and 32 and 6 and 18 months postpartum.

Follow-up and attrition: From age 11, children were invited to complete biannually, web-based questionnaires on current stage of puberty until full maturation or 18 years of age, whichever occurred first. Median age at entry was 11.1 years (25 – 75 percentile (p); 11.1 – 11.6 years) in boys and 11.1 years (25 – 75 p; 11.0 – 11.6 years) in girls. By October 2018, 94,625 questionnaires had been completed with an average of 6.0 (standard deviation: 3.6, range: 1 to 15), full sexual maturation had been reached in 5,068 children and 7,153 remained eligible for further follow-up.

Design and Measures: This is a longitudinal and population-based cohort. In the questionnaires, participants were asked to self-assess current height, weight and Tanner stage of pubic hair growth and breast or genital development. Children also reported the appearance of menarche (if yes; year and month), first ejaculation of semen (if yes; year and month), voice break, axillary hair growth and occurrence of acne.

Unique features: The DNBC Puberty Cohort’s large-scaled multiple measurements of a variety of pubertal milestones enable thorough examination of onset, progression and duration of puberty in both sexes. Available detailed information on early psychological, physiological, social and environmental exposures as well as on childhood mental and physiological health foster opportunities to explore important exposure windows and identify mediators of developmental changes of puberty. Maternal serum samples and umbilical cord samples are available in small quantities, and linkage with Danish registers and continued life-long follow-up facilitates investigation of health and disease after altered pubertal development.

Reasons to be cautious: Late age at entry warrants for cautious use of the data on early pubertal milestones. Based on self-assessment of current pubertal status, these data, primarily on Tanner staging, holds a risk of misclassification, which may be linked to exposures of interest. Initial recruitment in the DNBC and subsequent participation in the Puberty Cohort resulted in an overrepresentation of mother-child dyads from higher socioeconomic groups than the background population.

Collaborations and data access: The DNBC Puberty Cohort is an open access resource for researchers with a project that falls within the policy and overall aim of the DNBC. Applicants must submit an application form and a short protocol to the DNBC Steering Committee (dnbcresearch@ssi.dk). Funding and competing interests: Main funding was obtained from Independent Research Fund

All welcome