North Carolina Menopause Study
The North Carolina Menopause Study is a prospective study designed to assess timing of menopause among women in relation to organochlorine exposures, with exposure measurements taken during the reproductive years. It is a follow-up study of the women (mothers) who originally participated in the North Carolina Infant Feeding Study, an NIEHS study conducted between 1978 and 1982. Women were enrolled during pregnancy (n=856) into the infant feeding study, and polychlorinated biphenyls (PCBs) and DDE levels were analyzed in blood and breast milk samples collected around delivery. In 1992-1997, the Puberty Follow-up study of 600 of these children was conducted to examine the potential effects of these chemicals on the onset of puberty.
Data for the new study of age at natural menopause were collected in 2003-2004 when the median age of the mothers was 51 years. Six hundred and one of the original cohort of women were found, and 514 of these women completed interviews for the North Carolina Menopause Study. A computer-assisted telephone interview focused on reproductive and menstrual history with additional information collected on demographic, social and behavioral factors that could affect timing of menopause. A blood sample was collected from 285 participants based on sampling strata that involved criteria relating to age and menopausal status. The blood samples will be used to measure follicle stimulating hormone and luteinizing hormone levels to classify menopausal status of women with different menopause experiences:
- women who had undergone a hysterectomy with retention of at least one ovary
- women who are currently using hormone replacement therapy and whose use began while still having periods
- 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 the research team to assess the correlation between current (2003-2004) and baseline (1978-1982) PCB and DDE measures.
Relatively little is known about the effect of potential toxicants, including organochlorines such as PCBs and DDE, the long-lasting breakdown product of the pesticide DDT. One recent study conducted by epidemiologists at NIEHS and at the University of North Carolina at Chapel Hill reported an association between elevated blood levels of DDE and earlier age at menopause, but this was based on a cross-sectional study design. The North Carolina Menopause Study will provide more information about the relationship between menopause and exposure to organochlorine.