Women on estrogen therapy who consume large amounts of caffeine are more at risk of Parkinson's disease, but those drinking little or no caffeine have a reduced risk.

An intriguing interaction between estrogen and caffeine has been uncovered by researchers for the Nurses' Health Study. This involves data gathered over 18 years from a group of more than 77,000 women.

The study throws up a difference in the risk of Parkinson's disease among women taking estrogen replacement therapy. Those who consumed little or no caffeine had a reduced risk of the disease, compared to women not on estrogen. But those drinking five or more cups of coffee, as their main caffeine intake, actually had a higher risk of Parkinson's, again compared to women not taking estrogen.

Previous research in men has shown that increased caffeine intake reduces the risk of Parkinson's disease. The condition is, in any case, less common among women. It is interesting to see that estrogen use has such an impact upon Parkinson's disease risk but, given that the hormone is known to affect brain function, this is perhaps not surprising. What is unexpected is how the effect of estrogen depends upon caffeine use.

Source

Neurology 11th March 2003