Heritability of Age at Menarche and Menstrual Cycle Length in a Population Exposed to a Brominated Flame Retardant
Authors: Kira C. Taylor, Chanley M. Small, Michael P Epstein, Metrecia L. Terrell and Michele Marcus
Abstract: We determined the heritability of age at menarche and menstrual cycle length in a population exposed to a brominated flame retardant, polybrominated biphenyls (PBBs). We further investigated whether exposure to this potential endocrine disruptor affected the heritability of these traits. Methods: Our study population consisted of 373 families with variable PBB exposure. We estimated the heritability of self-reported age at menarche and menstrual cycle length using variance components methodology and assessed whether such heritability estimates varied by PBB exposure. Results: Age at menarche and menstrual cycle length were both heritable (heritability of age at menarche, 0.53±0.05; cycle length, 0.42±0.10). Heritability of age at menarche was higher in those with PBB levels at or below the limit of detection (0.60±0.07) than in the highly exposed group (0.38±0.12), although the difference did not reach statistical significance (χ2=2.50, p=0.11). Menstrual cycle length exhibited a non-significant trend similar to the menarche analysis when stratified by PBB exposure. Conclusions: This study provides support that age at menarche and menstrual cycle length are heritable. This study also demonstrates the utility of a method to investigate potential gene-environment interactions by examining heritability of a trait within strata of an environmental exposure.