Caffeine and risk of Parkinson's disease in a large cohort of men and women.

Caffeine consumption has been associated with a reduced risk of Parkinson's disease (PD). The association is strong and consistent in men, but uncertain in women, possibly because of an interaction with hormone replacement therapy (HRT). We sought to confirm these findings using data on PD incidence in the Cancer Prevention Study II Nutrition Cohort (CPS II-Nutrition), a large, prospective study of men and women. We conducted a prospective study of caffeine intake and risk of PD within the CPS II Nutrition Cohort. Intakes of coffee and other sources of caffeine were assessed at baseline. Incident cases of PD (n = 317; 197 men and 120 women) were confirmed by treating physicians and medical record review. Relative risks (RRs) were estimated using proportional hazards models, adjusting for age, smoking, and alcohol consumption. After adjustment for age, smoking, and alcohol intake, high caffeine consumption was associated with a reduced risk of PD. The RR comparing the 5th to the 1st quintile of caffeine intake was 0.43 (95% confidence interval [CI]: 0.26, 0.71; P trend = <0.002) in men, and 0.61 (95% CI: 0.34, 1.09; P trend = 0.05) in women. Among women, this association was stronger among never users of HRT (RR = 0.32) than among ever users (RR = 0.81; P interaction = 0.15). Consumption of decaffeinated coffee was not associated with PD risk. Findings from this large, prospective study of men and women are consistent with a protective effect of caffeine intake on PD incidence, with an attenuating influence of HRT in women. © 2012 Movement Disorder Society.