Caffeine, postmenopausal estrogen, and risk of Parkinson's disease.
BACKGROUND
Men who regularly consume caffeinated drinks have a lower risk of PD than do nondrinkers, but this relation has not been found in women. Because this sex difference could be due to hormonal effects, the authors examined prospectively the risk of PD according to use of postmenopausal hormones and caffeine intake among participants in the Nurses' Health Study.


METHODS
The study population comprised 77,713 women free of PD, stroke, or cancer at baseline, who were postmenopausal at baseline or reached menopause before the end of the study. During 18 years of follow-up the authors documented 154 cases of PD.


RESULTS
Overall, the risk of PD was similar in women using hormones and women who never used hormones (relative risk 1.02, 95% CI 0.69 to 1.52). Use of hormones, however, was associated with a reduced risk of PD among women with low caffeine consumption (RR 0.39, 95% CI 0.13 to 1.17), and with increased risk among women with high caffeine consumption (RR 2.44, 95% CI 0.75 to 7.86; p for interaction = 0.01). Among hormone users, women consuming six or more cups of coffee per day had a fourfold higher risk of PD (RR 3.92, 95% CI 1.49 to 10.34; p = 0.006) than did women who never drink coffee.


CONCLUSIONS
These results suggest that caffeine reduces the risk of PD among women who do not use postmenopausal hormones, but increases risk among hormone users. Clinical trials of caffeine or estrogens in women should avoid the combined use of these agents.
Ascherio
A
A
Department of Nutrition, Harvard School of Public Health, Boston, MA 02115, USA. Alberto.Ascherio@channing.harvard.edu
Chen
H
H
Schwarzschild
M A
MA
Zhang
S M
SM
Colditz
G A
GA
Speizer
F E
FE
D000328:Adult; D017668:Age of Onset; D000428:Alcohol Drinking / Q000453:epidemiology; D001628:Beverages / Q000706:statistics & numerical data; D002110:Caffeine / Q000008:administration & dosage; D003069:Coffee; D015331:Cohort Studies; D003278:Contraceptives, Oral, Hormonal / Q000008:administration & dosage; D004347:Drug Interactions; D015914:Estrogen Replacement Therapy / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008875:Middle Aged; D010298:Parity; D010300:Parkinson Disease / Q000453:epidemiology*; D011159:Population Surveillance; D017698:Postmenopause; D011446:Prospective Studies; D012307:Risk Factors; D012907:Smoking / Q000453:epidemiology; D011795:Surveys and Questionnaires
D003069:Coffee; D003278:Contraceptives, Oral, Hormonal; D002110:Caffeine