News Release

Caffeine and estrogen affect Parkinson's disease risk in postmenopausal women

Peer-Reviewed Publication

American Academy of Neurology

ST. PAUL, MN -- Women who consume little or no caffeine, but who take hormone replacement therapy, may reduce their risk of developing Parkinson's disease, according to a study published in the March 11 issue of Neurology, the scientific journal of the American Academy of Neurology. However, HRT may increase disease risk in women who drink the equivalent of more than five cups of coffee per day.

Two large studies have previously shown that increased caffeine intake is associated with a lower risk of Parkinson's disease in men. Studies in women, which to date have not factored in use of hormone replacement therapy, have been contradictory and inconclusive. Parkinson's disease is less common in women, and some evidence suggests that estrogen may help protect the neurons that degenerate in this disease. Estrogen is the principal hormone in HRT, a common therapy in post-menopausal women.

Eighteen years of data from more than 77,000 were drawn from the Nurses' Health Study. Information on hormone use and caffeine intake was collected from survey data.

Parkinson's disease was diagnosed in 154 of the women during the study. Similar to some previous studies, there was no difference in the incidence of disease between women who did or did not use HRT, when that was the only variable considered. However, when caffeine consumption was also factored in, some unexpected results emerged. In women who drank less than half a cup of coffee per day, HRT use was associated with a 65 percent reduction in relative risk of developing Parkinson's disease, compared to those who did not use HRT. These results are in keeping with the hypothesis that estrogen may help protect women against the brain cell death that causes Parkinson's disease. However, at the other extreme, in women who drank the equivalent of more than five cups per day, HRT seemed to have the opposite effect:the risk of developing PD was150 percent higher among women who used HRT than in those who did not use it.

Within these extremes of caffeine intake, HRT use or nonuse had little effect on the risk of developing PD.

All these risks were calculated after accounting for differences in cigarette smoking, which has been repeatedly shown to be associated with decreased risk of developing PD.

It was not possible to determine from the study whether the increased risk from the caffeine-HRT combination could be lessened by stopping use of one or the other.

"These results suggest that caffeine reduces the risk of Parkinson's disease among women who do not use postmenopausal hormones, but increases risk among hormone users," according to Alberto Ascherio, MD, lead study author and associate professor of Nutrition and Epidemiology in the Department of Nutrition at the Harvard School of Public Health. "Our results suggest that the inconsistency of the association between use of postmenopausal hormones and the risk of PD in previous studies could be due to a caffeine-estrogen interaction."

The results of this study do not by themselves warrant a change in use of HRT among postmenopausal women, according to Ascherio. "The indications for HRT use are a complex and controversial issue, but are mostly dependent on the effects of HRT on risk of cancer and other conditions that are by far more common than Parkinson's disease," he says. "Short term use for relief of menopausal symptoms should be considered on an individual basis, and independently of caffeine intake."

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This study was supported by the National Institutes of Health and by a gift from the Kinetics Foundation.

The American Academy of Neurology, an association of more than 18,000 neurologists and neuroscience professionals, is dedicated to improving patient care through education and research. For more information about the American Academy of Neurology, visit its website at www.aan.com.


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