September 16, 2002 01:38 PM ET NEW YORK (Reuters Health) - A review of medical studies confirms previously reported associations between smoking, coffee drinking and a lower risk of Parkinson's disease.

The results do not suggest that smoking cigarettes or drinking coffee will prevent Parkinson's, which is marked by a loss of certain brain cells that leads to tremor, rigidity and problems with balance and coordination. Any benefit of smoking, the authors stress, "would be overwhelmed by its effects on cancer, heart disease, respiratory disease, and overall mortality."

But understanding the nature of the relationship can help to identify the cause of Parkinson's and help researchers to discover ways to prevent it.

"Further research on the specific mechanisms involved in either case might lead to advances in the prevention and treatment of Parkinson's disease," Dr. Miguel A. Hernan from Harvard School of Public Health in Boston, Massachusetts and colleagues conclude.

Their analysis included 48 studies on cigarette smoking and Parkinson's disease and 13 studies on coffee drinking and Parkinson's. The review found a 60% lower risk of the disorder among current smokers. Previous smokers were also protected, although less so than current smokers, report researchers in the September issue of the Annals of Neurology.

Drinking coffee was associated with a 30% lower risk of the disease. In general, each additional cup of coffee lowered the likelihood of having Parkinson's by 10%, although the effects differed by gender. In women, moderate coffee intake appeared to provide the greatest protection, whereas greater amounts were the most protective in men.

The findings are not surprising, Dr. Karen Marder from Columbia University in New York City and colleagues note in an accompanying editorial. But a biological explanation for the connection has remained elusive, and some researchers have suggested that smoking itself is not protective. Rather, they say, some genetic characteristics may underlie both Parkinson's and the tendency to smoke.

"The major issue is whether smoking and coffee are solely responsible for the observed protective effects or whether they are merely intermediates in the causal pathway," Marder and colleagues write.

They suggest that studies investigating the effect of the age of disease onset and gender--particularly the influences of hormones--may provide clues about genetic or environmental factors that influence the development of Parkinson's disease.

"It is unlikely that either smoking or coffee alone protect against the development of Parkinson's disease. However, that they play a role in the complex gene environment interaction that result in Parkinson's disease appears to be quite plausible," the editorialists conclude.

SOURCE: Annals of Neurology 2002;52:261-262, 276-284.

-- Anonymous, September 17, 2002