Drinking coffee may reduce the risk of Parkinson's disease, according to a recent study by investigators from the Mayo Clinic, in Rochester, Minnesota. The reason for the association is unclear, but the study warns that this "does not imply that coffee has a direct protective effect against Parkinson's disease."

In a report published in the November 14th issue of Neurology, Dr. Demetrius M. Maraganore and colleagues identified 196 subjects who developed Parkinson's disease (PD) from 1976 to 1995. "Each case was individually matched by age and sex to a general population control subject" who was "free of PD, other parkinsonism, or tremor of any type." The medical records of all subjects were reviewed to abstract exposure information.

The researchers found that "coffee drinking was significantly more common in control subjects than cases." The investigators noted a "significant trend of decreasing risk with increasing number of cups per day." Furthermore, PD patients who drank coffee experienced a later onset of the disease than those who did not. These findings, the authors mention, agree with other reports that have shown an inverse association between coffee use and PD.

"The inverse association with coffee remained significant after adjustment for education, smoking, and alcohol drinking and was restricted to PD cases with onset at age [younger than] 72 years and to men," the authors state.

An association between PD and tobacco use was also demonstrated. Tobacco chewing or snuff use was "significantly more common in control subjects than cases." The association with tobacco smoking was similar, but it did not reach statistical significance.

Also, significantly more alcoholics were identified among the control subjects than among the PD patients. Although previous reports have demonstrated a relationship between alcohol consumption and a lower risk of PD, no such association was observed in this study.

The investigators suggest a premorbid personality, stimulant intolerance, or an underlying olfactory deficit may explain the low use of stimulants seen in PD patients. Another possibility, the authors mention, is that coffee use, smoking, and drinking alcohol may have a direct protective effect against PD.

Caffeine has been shown in some studies to block adenosine receptors. "Interestingly, the adenosine A-2A receptor modulates the nigrostriatal dopamine system, and antagonists of that receptor have been proposed as therapy for PD," the authors report.

"Against a causal association between coffee, smoking, and possibly alcohol and PD is the lack of specificity. Caffeine, nicotine, and alcohol have different pharmacologic or metabolic effects on the brain," the authors state.

Reached for comment, Dr. Maraganore told Reuters Health that a study earlier this year showed similar findings. Many patients asked if they should be consuming more coffee, he said. Dr. Maraganore emphasized that one must look at the whole picture and not simply assume that coffee prevents PD.

(From Reuters)