Prevention of Parkinson's Disease
Epidemiological Studies
Overall, the results of case-control studies suggest that coffee and caffeine intakes are inversely associated with the risk of Parkinson's disease. 66 Several large prospective cohort studies have also found inverse associations between coffee and caffeine intakes and Parkinson's disease risk in men (Table 2). A study of more than 8,000 Japanese-American men found that those who did not drink coffee were 3–5 times more likely to develop Parkinson's disease over the next 24–30 years than those who drank at least 28 oz daily. 67 Caffeine intakes from coffee and other sources were also inversely associated with Parkinson's disease risk. Similarly, in the Health Professionals Follow-up Study, men who regularly consumed at least one cup of coffee daily had a risk of developing Parkinson's disease over the next 10 years that was about half that of men who did not drink coffee. 3 The consumption of tea and other caffeinated beverages was also inversely associated with Parkinson's disease risk. In contrast, inverse associations between coffee and caffeine consumption and Parkinson's disease risk over a 16-year period were not observed in the Nurses' Health Study. 3 Similarly, in the Cancer Prevention Study (CPS) II cohort of more than 500,000 men and women in the US, coffee consumption was inversely associated with Parkinson's disease mortality in men but not women. 68 The failure of prospective studies to find an inverse relationship between coffee consumption and Parkinson's disease in women may be due to the modifying effect of estrogen replacement therapy. 69 Further analysis of the Nurses' Health Study cohort revealed that coffee consumption was inversely associated with Parkinson's disease risk in women who had never used postmenopausal estrogen, but a significant increase in Parkinson's disease risk was observed in postmenopausal estrogen users who drank at least 6 cups of coffee daily. 70 In the CPS II cohort, a significant inverse association between coffee consumption and Parkinson's disease mortality was also observed in women who had never used postmenopausal estrogen, but not in those who used postmenopausal estrogen. 68 It is not clear how estrogen use modifies the effect of caffeine on Parkinson's disease risk. However, caffeine is largely metabolized by hepatic CYP1A2, and the use of postmenopausal estrogen replacement therapy has been found to inhibit CYP1A2-mediated caffeine metabolism. 71