The Pharmaceutical Journal
Vol 270 No 7240 p358
15 March 2003

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Parkinson's disease, hormone therapy and caffeine intake — is there a link?

A protective effect of caffeine against the onset of Parkinson's disease may be reversed in women who use hormone replacement therapy (HRT).

So found United States scientists investigating why caffeine appears to protect men but not women against Parkinson's disease. Proposing that hormonal effects could be to blame, they examined the risk of the disease according to both use of HRT and caffeine intake. They used the records of over 77,000 women who had been followed up for 18 years as part of the US Nurses Health Study.

Overall, the risk of Parkinson's disease was similar in women who had used hormones postmenopausally and those who had never done so. However, use of HRT reduced the risk of the disease in women with low caffeine consumption (relative risk 0.39, 95 per cent confidence interval 0.13–1.17). High caffeine consumption and HRT use increased the risk of Parkinson's disease (2.44, 0.75–7.86, P=0.01 for interaction). Women using HRT who drank six or more cups of coffee per day were four times more likely to develop the condition.

The authors say that inconsistencies in studies looking at HRT and Parkinson's disease could be due to a caffeine-oestrogen interaction. They conclude that clinical trials of caffeine or oestrogens in women should avoid the combined use of these agents.

They note that conversion of caffeine to its primary metabolite is markedly inhibited by oestrogen in oral contraceptives or HRT products (Neurology 2003;60:790).