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Parkinson's Disease and Pesticide Exposure: New Research

by aseligmann — last modified Jul 21, 2010 12:00 AM

Parkinson's disease affects mostly older people and is characterized by tremors, rigidity, slow movements, and poor balance. It appeared to be a new disease when it was first described as a "shaking palsy" almost 200 years ago.

Parkinson's disease affects mostly older people and is characterized by tremors, rigidity, slow movements, and poor balance. It appeared to be a new disease when it was first described as a "shaking palsy" almost 200 years ago.

The interest in pesticides and Parkinson's disease started in the early 1980s when a doctor treated a younger patient who suddenly displayed symptoms of Parkinson's. He and another doctor who encountered this scenario linked these symptoms to the chemical MPTP in a botched batch of synthetic heroin. The realization that the chemical structure of MPTP was very similar to paraquat, a widely-used herbicide, set off frenzy of research.

Since then, scientists have examined both genetic and environmental factors in the development of Parkinson's disease. Pesticide exposure has been a top focus for environmental factors. Laboratory studies of animals have shown how Parkinson's might be linked to some specific pesticides including paraquat (herbicide), rotenone (insecticide), dieldrin (insecticide), and maneb (fungicide). Figuring out the picture for humans is more complicated.

Researchers have undertaken surveys of human health in order to see who is more likely to get Parkinson's disease. While these health studies have had conflicting conclusions regarding pesticide exposure, many have indicated a relationship between Parkinson's and pesticides.

Two new surveys bolster the evidence that pesticide exposure increases the risk of Parkinson's disease.

Mayo Clinic

Researchers at the Mayo Clinic identified people who were diagnosed with Parkinson's disease over a 19-year period in Olmsted County, Minnesota. They compared each of these people to another resident of the same sex and age who did not have the disease. Through interviews, they questioned the 270 participants about their exposure to chemical products in either occupational or non-occupational settings.

The results showed that men who were exposed to pesticides - in their work or elsewhere - were 2.4 times more likely to have Parkinson's disease than men who didn't use pesticides.

In this study, women who were exposed to pesticides did not have a higher risk of Parkinson's. Researchers noted that women are generally less exposed to pesticides than men, but factors such as estrogen might have a protective effect.

Harvard School of Public Health

A much larger study examined data from over 140,000 people who were participating in a study sponsored by the American Cancer Society. In a 1982 questionnaire, they had reported on their occupations and on their exposure to certain chemicals and dusts. Over 7,800 reported exposure to pesticides in occupational or non-occupational settings.

Between 1992 and 2001 they responded to more study surveys. In the 2001 survey, they were asked for the first time if they had Parkinson's disease. Researchers were then able to compare information about people with Parkinson's to the rest of the study group.

Farming would be expected to be a risk factor for Parkinson's because of higher pesticide exposure. Analysis of data in this study showed that men and women who had been classified as "farmer, rancher, or fisherman" in 1982 did not appear to be at higher risk for Parkinson's disease than non-farmers.

However, as a group, all people who reported any pesticide exposure were 70% more likely to have Parkinson's disease than those who reported no exposure to pesticides. This was true for both men and women.

It appeared that home and garden pesticide use was a risk factor for people who were not exposed in their jobs.

Conclusion

Scientists are not saying that pesticide exposure 'causes' Parkinson's disease. Evidence is showing that Parkinson's disease is likely influenced by a combination of various genetic and risk factors.

 


NEWS STORIES

Study concludes that pesticide use increases risk of Parkinson's in men.
Lucier, Lisa, Mayo News Bureau. June 14, 2006
http://www.mayoclinic.org/news2006-rst/3496.html

Pesticides exposure associated with Parkinson's disease.
Datz, Todd, Harvard School of Public Health. June 26, 2006.
http://www.hsph.harvard.edu/press/releases/press06262006.html

Research bolsters link of pesticides to Parkinson's
Cone, Marla (Los Angeles Times)
Seattle Times. December 8, 2005.
http://seattletimes.nwsource.com/html/nationworld/2002671171_parkinsons08.html

ARTICLES

Frigerio, R, et al. 2006. Chemical exposures and Parkinson's disease: a population-based case-control study. Movement Disorders 21(10):1688-1692

Ascherio, A et al. 2006. Pesticide exposure and risk of Parkinson's disease. Annals of Neurology 60:197-203