Female reproductive factors, menopausal hormone use, and Parkinson's disease.

The objective of this study was to examine the associations of reproductive factors and exogenous hormone use with risk of Parkinson's disease (PD) among postmenopausal women. The study comprised 119,166 postmenopausal women aged 50 to 71 years in the NIH-AARP Diet and Health Study, who completed a baseline questionnaire in 1995-1996 and a follow-up survey in 2004-2006. A total of 410 self-reported PD diagnoses were identified between 1995 and 2006. Multivariate odds ratios (ORs) and 95% confidence intervals (CIs) were derived from logistic regression models. PD risk was not significantly associated with female reproductive factors including age at menarche, age at first live birth, parity, and age at menopause. For example, compared with women with natural menopause at age 50 to 54 years, the ORs were 1.18, (95% CI, 0.78-1.79) for women with natural menopause aged <45, 1.19 (95% CI, 0.88-1.61) for those aged 45 to 49, and 1.33 (95% CI, 0.91-1.93) for those aged 55 or older. We found that oral contraceptive use for ≥10 years (vs. never used) was associated with lower PD risk (OR, 0.59; 95% CI, 0.38-0.92), but shorter use showed no association. Use of menopausal hormone therapy showed inconsistent results. Compared with non-hormone users at baseline, current hormone users for <5 years showed a higher risk of PD (OR, 1.52; 95% CI, 1.11-2.08). However, no associations were observed for past hormone users or current users of ≥5 years. Overall, this large prospective study provides little support for an association between female reproductive factors and PD risk. Our findings on long-term oral contraceptive use and current hormone therapy warrant further investigations.