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 ages 50–71 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 (OR) and 95% confidence intervals (CI) 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 ages 50–54 years, the ORs were 1.18, (95% CI 0.78–1.79) for women with natural menopause at ages <45, 1.19 (0.88–1.61) for ages 45–49, and 1.33 (0.91–1.93) for ages 55 or later. We found that oral contraceptive use for ≥10 years (vs. never use) was associated with lower PD risk (OR=0.59; 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 of <5 years showed a higher risk of PD (OR=1.52; 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.