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July 10, 2007 Smoking may reduce risk of Parkinson’s disease Joanna Carpenter Smokers are less likely to develop Parkinson’s disease, research suggests. According to a large-scale review of studies, a better understanding of how smoking protects from Parkinson’s disease could also lead to a better understanding of the condition, its prevention and treatment. About one in 500 people in Britain have Parkinson’s. Researchers have long suspected that there is a link between cigarette smoking and a reduced risk of Parkinson’s, a progressive neurological disease that affects movement. However, the number of participants in previous studies was too small for the results to be rigorously confirmed by the statistics. The research, published in the July issue of Archives of Neurology, overcame this by pooling data on 11,809 individuals involved in 11 previous studies conducted between 1960 and 2004. This larger sample size is big enough to make the study’s findings statistically significant. The authors found that smokers were less likely to get Parkinson’s, and those who smoked more seemed to have greater protection. These findings indicate that smoking may delay rather than prevent the onset of Parkinson’s, but that would have to be confirmed by a larger study. “Current smokers and those who had continued to smoke to within five years of Parkinson’s disease diagnosis exhibited the lowest risk, [but] a decrease in risk [of] 13 to 32 per cent was also observed in those who had quit smoking up to 25 years prior,” said Dr Beate Ritz, of the UCLA School of Public Health in Los Angeles, and her co-authors. While the research provides statistically significant evidence of associations between smoking and protection from Parkinson’s for the first time, it gives only clues as to what the mechanism might be. A potential explanation is the biochemistry of the brain. In Parkinson’s, nerve cells – dopaminergic neurons – are lost in the part of the brain that controls movement. Dr Ritz and coworkers speculate that a substance in cigarette smoke may protect those nerve cells. Genetics may also play a role. “The risk reductions we observed for white and Asian patients were not seen in Hispanic and African American patients,” the authors said. However, they could not rule out that this could be due to better diagnosis of the disease in white and Asian patients rather than genetic factors. ---------------------------------------------------------------------- To sign-off Parkinsn send a message to: mailto:[log in to unmask] In the body of the message put: signoff parkinsn