March 12, 2003 -- Hormone replacement therapy reduces a woman's risk of Parkinson's disease -- if she's not a coffee drinker. A new study suggests caffeine reduces Parkinson's risk in women who don't take HRT -- but increases it in women who do take HRT.
The findings help explain a puzzling fact. Men who drink coffee have a lower Parkinson's risk. The same never seemed to be true of women. Why? It now seems that caffeine interacts with the female hormone estrogen, the main ingredient in HRT.
A research team led by Alberto Ascherio, MD, a professor at the Harvard School of Public Health, examined data from the Nurses' Health Study. This study collected data on more than 77,000 women over 18 years.
Reporting in the March 11 issue of Neurology, Ascherio's team found that HRT reduced a woman's already-small risk of Parkinson's disease by 65% -- if she drank less than a half cup of coffee a day. Women who used HRT and drank more than five cups of coffee a day had a 150% higher risk of Parkinson's.
"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," Ascherio says in a news release.
However, Ascherio notes that these findings are no reason for women to use -- or not to use -- HRT.
"Short-term use [of HRT] for relief of menopausal symptoms should be considered on an individual basis and independently of caffeine intake," he says.