WEDNESDAY, March 10, 2010 (HealthDay News) -- In an effort to understand the relationship between tobacco smoke and Parkinson's disease, researchers have found that smoking for many years may reduce risk for the disease but smoking a large number of cigarettes a day does not seem to reduce risk.
Previous research had suggested that smokers have a lower risk of developing Parkinson's disease.
The finding, however, comes with a caveat.
"Given the many adverse consequences of smoking, no one would suggest smoking in order to prevent Parkinson's disease," study author Dr. Honglei Chen, of the U.S. National Institute of Environmental Health Sciences, said in a news release from the American Academy of Neurology.
Rather, he said, the results "could guide the development of studies on various tobacco components with animal models to help understand the relationship between smoking and Parkinson's disease."
"Research to reveal the underlying chemicals and mechanisms is warranted," Chen said. "Such studies may lead to a better understanding of the causes of Parkinson's disease."
The study included 305,468 people, 50 to 71 years old, who provided information about their diet and lifestyle when they were enrolled and again 10 years later. In that span, 1,662 (about 0.5 percent) of the participants developed Parkinson's disease.
Compared with people who'd never smoked, current smokers were 44 percent less likely to have developed Parkinson's, and former smokers were 22 percent less likely. Further analysis revealed that the length of time people smoked affected their risk. Those who'd smoked for 40 years or more were 46 percent less likely to develop Parkinson's than those who'd never smoked, and the risk was 35 percent less for after 30 to 39 years of smoking and 8 percent less for those who'd smoked one to nine years.
The number of cigarettes a person smoked a day, however, did not affect the risk for developing Parkinson's disease, according to the study.
The study was published online March 10 in Neurology.
We Move has more about Parkinson's disease.