Childhood Socioeconomic Position and Pubertal Onset: Implications for Breast Cancer

Abstract

Abstract Higher socioeconomic position (SEP) has been associated with increased risk of breast cancer. Its relationship with the age of menarche, which is inversely associated with risk of breast cancer, and to the age of pubertal onset, is less clear. We studied the relationship of SEP to pubertal onset in a multiethnic cohort of girls aged 6–8 years at baseline and followed for 5–8 years in the Breast Cancer and the Environment Research Program in three study sites across the United States that included annual clinical examinations performed from 2004 to 2012. Analyses were conducted with accelerated failure time models using a Weibull distribution, with left, right and interval censoring. Among 1059 girls, an index of SEP comprised of household family income, mother's education and whether the home was owned or rented was assessed for associations with pubertal onset, measured by breast budding (Tanner Stage B2) and pubic hair development (Tanner Stage PH2). Girl's BMI% at entry to the study and black or Hispanic race/ethnicity were the strongest predictors of age at pubertal onset by both measurements, but the SEP index was an independent predictor in adjusted models. Girls from the lowest quintile of SEP entered puberty on average 6% earlier (6.0–7.5 months) than girls from the highest quintile (time ratio = 0.94, 95% confidence interval 0.91–0.97) adjusted for BMI%, race/ethnicity and their interaction. The meaning of SEP in this relationship bears further study, but our results suggest that early life social circumstances beyond race/ethnicity and body size may influence the timing of pubertal development.