Caffeine May Reduce the Risk of Parkinson's Disease in Some Women

Laurie Barclay, MD

November 10, 2004

Nov. 10, 2004 — Caffeine may reduce the risk of Parkinson's disease but estrogen therapy may inhibit that benefit, according to the results of a prospective cohort study published in the November issue of the American Journal of Epidemiology.

"Caffeine consumption is associated with a reduced risk of Parkinson's disease in men but not in women," write Alberto Ascherio, from the Harvard School of Public Health in Boston, Massachusetts, and colleagues. "This gender difference may be due to an interaction between caffeine and use of postmenopausal estrogens."

Using the Cancer Prevention Study II, a cohort of more than one million people enrolled in 1982, the investigators determined causes of death from death certificates in 1989 through 1998. In 909 men and 340 women, Parkinson's disease was listed as a cause of death.

Coffee consumption was inversely associated with Parkinson's disease mortality in men (P for trend = .01) but not in women (P = .60) after adjustment for age, smoking, and alcohol intake. In women, this association was dependent on postmenopausal estrogen use. Compared with nondrinkers of coffee, the relative risk for women drinking four or more cups (600 mL) of coffee per day was 0.47 (95% confidence interval [CI], 0.27 - 0.80; P = .006) among never-users of estrogen and 1.31 (95% CI, 0.75 - 2.30; P = .34) among users.

"These results suggest that caffeine reduces the risk of Parkinson's disease but that this hypothetical beneficial effect may be prevented by use of estrogen replacement therapy," the authors write. "This potential interaction should be considered in the design of randomized trials assessing the effects of caffeine or estrogen in the progression of Parkinson's disease."

Study limitations include the absence of information on Parkinson's disease diagnoses among surviving participants and on changes in coffee consumption or estrogen use during follow-up.

The National Institutes of Health and the Michael J. Fox Foundation and Kinetics Foundation supported this study.

Am J Epidemiol. 2004;160:977-984

Reviewed by Gary D. Vogin, MD


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