Most doctors agree that smoking cigarettes poses a significant health danger and should be avoided, however, new data suggest that the habit may have a least one health benefit--it may lower the risk of developing Parkinson's disease. In a study of over 300,000 adults, researchers found that the more years people smoked, the lower their risk of Parkinson's disease. Among smokers who used at least a pack a day for less than 10 years, there was a 4 percent reduction in the risk of developing Parkinson's. Those who smoked for 30 years or more, meanwhile, were 41 percent less likely to develop the disease than non-smokers.