Environmental exposures may alter the timing of breast development, a risk factor for reproductive function, breast cancer, and other chronic diseases. Mount Sinai is one of three Breast Cancer and Environment Research Centers (BCERCs) sites investigating the role of environmental exposures in puberty. We are studying inner city minority girls who are at risk for obesity and early development. We have established a cohort of 412 girls (60% Hispanic, 40% black; 6-8 years old at baseline [BL]). At first annual followup (FU1) we have seen 296 girls as of September 10, 2008. Breast stage was assessed by health providers (BL, FU1); dietary isoflavone and energy intake, urinary biomarkers of phthalates, phenols, and phytoestrogens were measured at BL. Breast development (stage B2+ vs B1) was present in 22% of girls at BL, and in 35% at FU1. Many girls were at-risk-for- or were overweight (40% at BL). Baseline isoflavone and energy intakes were lower among girls who were B2+ vs B1 at BL as well as at FU1 (not significant). Baseline low-molecular-weight phthalate urinary metabolites (LMWPH) were higher among girls who were B2+ vs B1 at FU1; however they did not differ by BL breast stage (unadjusted). We calculated adjusted prevalence ratios (PR) and hazards ratios (HR) for cross-sectional and longitudinal observations. Age- and ethnicity- adjusted prevalence ratios (PR) for B2+ at FU1 were 1.14 per log-LMWPH (95%-CI 0.996-1.30) measured at BL. Other urinary biomarkers had near-null PRs for breast stage at BL or FU1 (benzophenone, bis-phenol A, 2,5-dichlorophenol, triclosan, genistein, daidzein, enterolactone, high-molecular-weight phthalate monoesters). Interaction models indicate that prevalance of breast stage may vary by adiposity for several biomarkers including phthalate metabolites, benzophenone, bisphenol A, and enterolactone. Similarly, HR models predicting age at B2 showed few significant main effects, but there was increased risk for one biomarker among girls with above-median-BMI and above-median-exposure biomarkers at BL. in summary, preliminary results from this longitudinal study suggest few main associations of hormonal environmental exposures with breast development, although effects may be observed among underweight or overweight girls. Further analyses with complete followup may provide additional insights. Disclaimer: The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the Centers for Disease Control and Prevention.
This research was supported by grants from NIEHS (ES009584 and ES012645), EPA (R827039 and RD831711), ATSDR (ATU 300014), NCI (CA93447), and NCRR MO1-RR-00071. We thank Charles Dodson for his valuable support of this project.