(Beyond Pesticides, March 31, 2008) Researchers studying related individuals who share environmental and genetic backgrounds find an association between pesticide use and Parkinson’s disease. The strongest links were between the disorder and use of herbicides and insecticides, such as organochlorines and organophosphates. The study, “Pesticide exposure and risk of Parkinson’s disease: a family-based case-control study,” was published March 28 online in the journal BMC Neurology.
The research team from Duke University Medical Center and the University of Miami Miller School of Medicine Morris K. Udall Parkinson Disease Research Center of Excellence recruited 319 patients and over 200 relatives. They used telephone interviews to obtain histories of pesticide exposure, living or working on a farm, and well-water drinking. No association was found between Parkinson’s disease and well-water drinking or living or working on a farm, which are two commonly used proxies for pesticide exposures.
Parkinson’s disease is a common neurological disorder affecting about 1 million people in the U.S. The disorder typically develops in later life resulting in symptoms such as tremors and muscle rigidity. Although variations in several genes have been identified that contribute to the disease, these rare genetic defects account for a small proportion of the overall prevalence of the disorder. The majority of Parkinson’s disease cases are thought to be due to an interaction between genetic and environmental factors.
“Previous studies have shown that individuals with Parkinson’s disease are over twice as likely to report being exposed to pesticides as unaffected individuals” says the study’s lead author, Dana Hancock, “but few studies have looked at this association in people from the same family or have assessed associations between specific classes of pesticides and Parkinson’s disease.”
Previous studies have also supported pesticides as a risk factor for Parkinson’s disease. A Harvard School of Public Health study of more than 140,000 adults found that those exposed to long-term, low levels of pesticides had a 70 percent higher incidence of Parkinson’s. Researchers have found that the risk factor for developing Parkinson’s increases with high levels of pesticide exposure. Low-level exposure to dieldrin, a banned but persistent organochlorine pesticide lingering in the environment, appears to accelerate changes in the brain that can potentially lead to the onset of Parkinson’s disease symptoms years or even decades before they might naturally develop, according to a 2006 study. Among the literature that links paraquat to Parkinson’s is an April 2007 study that finds farm workers exposed to paraquat have twice the expected risk of developing Parkinson’s. For more information on pesticides’ link to Parkinson’s disease, click here.