The findings suggest that both genetic and environmental factors may influence the development of Parkinson's, a progressive neurodegenerative disease marked by trembling of the arms and legs, stiffness and rigidity of the muscles and slowness of movement.

Previous studies have suggested that smokers and coffee drinkers have a lower risk of developing Parkinson's disease. However, this is the first study to look specifically at cigarette smoking and caffeine consumption within families affected by the disease, the researchers said.

Smoking cigarettes and consuming copious amounts of caffeine carry their own risks and should not be taken up in an attempt to avoid developing Parkinson's disease, cautions study investigator Burton L. Scott, M.D., Ph.D., associate professor of medicine.

The findings were published in the April 2007 issue of the journal Archives of Neurology. The research was funded by the National Institute of Neurological Disorders and Stroke.

The researchers studied the associations between smoking, caffeine and Parkinson's disease in 356 Parkinson's disease patients and 317 family members without the disease.

Individuals with Parkinson's disease were half as likely to report ever smoking and a third as likely to report current smoking compared with unaffected relatives, the researchers found.

Individuals with Parkinson's disease were also less likely to drink large amounts of coffee, the researchers found.

The biological mechanisms through which smoking and caffeine might work in individuals at risk of Parkinson's disease are still not clear, said study co-investigator Mark A. Stacy, M.D., associate professor of medicine and director of the Duke Movement Disorders Center.

"Smoking and caffeine may modify underlying genetic susceptibilities that exist in families with Parkinson's disease, but further work is needed to see how this interaction ultimately plays out," Stacy said.

Source: Duke University Medical Center