Organochlorine Exposure in Relation to Timing of Natural Menopause

Smoking has been shown in many studies to be associated with a 1-2 year decrease in age at natural menopause. However, relatively little is known about the effect of other potential toxicants, including organochlorines such as polychlorinated biphenyls (PCBs), and 1, 1 dichloro-2,2-bis(p-chlorophenyl) ethylene (p,p -DDE, referred to subsequently as DDE). We will assess timing of menopause among women who participated in the North Carolina Infant Feeding Study (total n = 865). Recruitment for this study was conducted between 1978 and 1982. PCB and DDE levels were analyzed in blood and breast milk samples around delivery and after pregnancy. The median age of the women as of March, 2002, is 50 years. Data will be collected in a telephone interview focusing on reproductive and menstrual history with additional information collected on demographic, social and behavioral factors that could affect timing of menopause. A blood sample will be collected from approximately 50% of participants based on sampling strata that involve criteria relating to age and menopausal status. Follicle stimulating hormone and luteinizing hormone will be measured in these samples in order to classify menopausal status of women who had undergone hysterectomy with retention of at least one ovary, women who are currently using hormone replacement therapy whose use began while still having periods, and women who report very short, very long, or irregular menstrual cycle lengths during the past 12 months. PCB and DDE levels will also be determined in these samples, allowing us to assess the correlation between current and baseline (1978-1982) PCB and DDE measures. The purpose of this study is to assess the association between the baseline organochlorine measurements and timing of natural menopause. A secondary aim will be to conduct exploratory analyses of the association between specific factors (e.g., pregnancy history, weight change) and rate of change in organochlorine levels.