Mar. 23 --

TUESDAY, July 10 (HealthDay News) -- Long-term and current smokers have a lower risk of Parkinson's disease than the general population, researchers say in a report that confirms previous observations that people with Parkinson's disease were less likely to be smokers.

Dr. Beate Ritz of the University of California, Los Angeles, School of Public Health and colleagues analyzed data from 11,809 people involved in 11 studies conducted between 1960 and 2004. Of those, 2,816 individuals had Parkinson's disease.

The data showed that current smokers and those who had continued to smoke within five years of Parkinson's disease diagnosis had the lowest risk. People who quit smoking up to 25 years before diagnosis also had a reduced risk. Other tobacco products such as cigars, pipe tobacco and chewing tobacco showed reduced risk as well.

The association between tobacco use and Parkinson's disease disappeared for people older than 75, however. And while the association was strong for people of Caucasian or Asian ancestry, it did not hold for Hispanics or blacks.

The researchers wrote that the biochemical basis for the effect is not well understood, but that either nicotine or carbon monoxide may, in fact, protect brain cells that produce dopamine. Dopamine is a chemical produced in the brain that enables the body to coordinate movement. Once 80 percent of the neurons that produce dopamine begin to fail, the symptoms of Parkinson's disease appear. Symptoms include tremors in hands and feet and a lack of flexibility or balance.

Writing in the July issue of the Archives of Neurology, the researchers called or further research to understand what chemicals in cigarettes and tobacco might be protective against Parkinson's disease.

More information

To learn about Parkinson's disease, visit the Parkinson's Disease Foundation.

SOURCE: Archives of Neurology, news release, July 9, 2007