In women who’ve passed menopause, use of estrogen replacement determines whether drinking caffeine protects against Parkinson’s disease or not, new research indicates.

Numerous studies, including one by the current research team, have shown an association between caffeine intake and a decreased risk of Parkinson’s disease. However, this apparent benefit of caffeine was diminished or absent in women.

The gender difference might be explained by estrogen, and this prompted Dr. Alberto Ascherio, from the Harvard School of Public Health, and colleagues to analyze data from subjects who participated in the Cancer Prevention Study II, which began in 1982 and included more than 1 million participants.

“During follow-up, 60,631 men and 37,486 women died from any cause,” the researchers report in the American Journal of Epidemiology. Of these subjects, 909 men and 340 women had Parkinson’s disease listed as the cause of death.

Consistent with previous reports, the overall analysis showed that the risk of death due to Parkinson’s fell as coffee intake increased in men, but not in women. However, on further analysis, women who had never used estrogen replacement therapy did seem to experience the anti-Parkinson’s benefits of caffeine.

Among women who never used estrogen, drinking 4 or more cups of coffee per day reduced the risk of dying from Parkinson’s disease by 53 percent compared with never drinking coffee. On the other hand, coffee intake made no difference among women who used estrogen.

This report “suggests that it may be important to investigate the mechanisms of a possible interaction between estrogen and caffeine in the (cause) of Parkinson’s disease,” the authors conclude.

SOURCE: American Journal of Epidemiology, November 15, 2004.