Lifetime exposure to estrogens and Parkinson's disease in California teachers

Abstract Introduction Parkinson's disease (PD) is consistently observed to occur less frequently in women than men, prompting investigation into whether estrogen protects against neurodegeneration of dopaminergic neurons. Methods We used baseline data in the California Teachers Study, a prospective cohort of women, to investigate whether reproductive factors indicating higher long-term estrogen levels are associated with PD using a nested case-control approach. We identified 228 PD cases and 3349 unaffected controls frequency matched by age and race. Results Women who reported using combined estrogen/progesterone therapy or progesterone only formulations had a 57% increase in PD risk (OR = 1.57, 95% CI = 1.06, 2.34) compared to never having used HT. Compared to women with menopause at 50–52 years, menopause at younger ( Conclusions These results provide some support for the hypothesis that lifelong high estrogen is protective in PD, suggesting that the level and persistence of exposure over the long term may be important in PD risk reduction.