The study, which will appear in the July issue of Annals of Neurology and also will appear online via Wiley Interscience, shows that individuals reporting exposure to pesticides had a 70 percent higher incidence of Parkinson's than those not reporting exposure. According to the study, no increased risk of Parkinson's was found from reported exposure to other occupational hazards, including asbestos, coal or stone, dust chemicals, acids or solvents.
The study also suggests that individuals who were exposed to pesticides used in gardens and backyards showed a higher risk of Parkinson's.
Previous studies suggested a link between Parkinson's and low-level exposure to pesticides, though the data remains inconclusive. The researchers, led by Alberto Ascherio, associate professor of nutrition and epidemiology at Harvard School of Public Health, used data from a study of the link between diet and cancer, begun in 1992. Of the volunteers who filled in the original data, 143,325 responded in 2001 to a follow-up survey to see how they had fared. Of these, 413 had developed Parkinson's since the start of the study.
Researchers found that 1,956 farmers, ranchers or fishermen were 14 times more likely to be exposed to pesticides compared with people in other occupations. Blue-collar workers had a two-fold higher risk of exposure to pesticides.
Even after adjustment of other risk factors including age, gender and smoking status, the risk of Parkinson's still was significant among those who were exposed to pesticides, 1.7 times higher than that for those who were not exposed.
Earlier this month, a study published in the journal Movement Disorders found that the men with Parkinson's were 2.4 times more likely to have had exposure to pesticides than those who did not have Parkinson's. Ascherio said that future studies will need to examine which specific pesticides or classes of pesticides are likely to cause Parkinson's disease.
An estimated 1.5 million Americans have Parkinson's, which is a chronic, progressive degenerative brain disorder. It causes shaking, rigidity and slowness of movement.
Actor Michael J. Fox, who is living with the disease, was one of the major financers of the study, which he did through the Michael J. Fox Foundation.
The article can be found at www3.interscience.wiley.com/cgi-bin/abstract/112660877/ABSTRACT?CRETRY=1&SRETRY=0.