Exposure to estrogen and women's risk for Parkinson's disease: A prospective cohort study in Denmark

Background: Studies have suggested that estrogen is protective against Parkinson's disease; however, the results have been inconsistent. Methods: Our cohort comprised 27,466 women from the prospective Diet, Cancer and Health study. At inclusion, all the cohort members filled in questionnaires on diet and lifestyle, including reproductive factors, use of hormone products, and smoking habits. The cohort was followed up for Parkinson's disease in the Danish Hospital Register, and risks associated with indicators of exposure to estrogen were estimated in a Cox proportional hazards model. Results: No significant association was found between reproductive factors and risk for Parkinson's disease. Use of oral contraceptives was associated with a nonsignificantly increased risk (hazard ratio, 1.30; 95% confidence interval, 0.81-2.09), as was use of hormone replacement therapy (1.41; 0.90-2.21). Conclusions: Our data do not support the hypothesis of a protective effect of estrogen on the risk for Parkinson's disease in women. (C) 2013 Elsevier Ltd. All rights reserved.