New research from the US has suggested that patients with Parkinson’s disease were significantly more likely to have been exposed to pesticides than unaffected family members.

The study is published in the open access online journal BMC Neurology and is the work of investigators from the Duke University Medical Center in Durham, North Carolina, and the University of Miami Miller School of Medicine Morris K Udall Parkinson Disease Research Center of Excellence in Miami, Florida.

There are approximately 1 million Americans living with Parkinson’s disease, a common neurological disorder that typically starts in later years and whose symptoms include tremors and rigid muscles.

Some studies have found rare gene variants account for a small percentage of overall cases, but most are believed to arise from the interaction of genes with the environment.

Lead author Dr Dana Hancock explained that:

“Previous studies have shown that individuals with Parkinson’s disease are over twice as likely to report being exposed to pesticides as unaffected individuals.”

“But,” said Hancock, “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”.

By examining family members who shared a potential genetic predisposition to Parkinson’s, the investigators were able to look for differences in environmental exposure between those members that had the disease and those that did not.

Hancock and colleagues recruited 319 patients with Parkinson’s and over 200 of their relatives and interviewed them on the phone to find out how they might have been exposed to pesticides, such as from handling or being exposed to specific types, or by working or living on a farm, or drinking water from wells.

When they analysed the results they found a signficant link between pesticide exposure and Parkinson’s disease. The strongest link was between the disease and exposure to herbicides and pesticides like organochlorides and organophosphates.

No significant links were found between Parkinson’s and well-water drinking, or living or working on a farm, which are often described as “commonly used proxies for pesticide exposures”.

Commenting on the findings, Hancock said that many studies have suggested pesticides as a risk factor for Parkinson’s, but like this one, they lack the bilogical evidence.

She called for further studies to look more closely into the biological mechanisms linking pesticides to Parkinson’s, and that future genetic studies should consider the possibility that pesticides may trigger Parkinson’s in people with a genetic predisposition to the disease.

“Pesticide exposure and risk of Parkinson’s disease: a family-based case-control study.”
Dana B Hancock, Eden R Martin, Gregory M Mayhew, Jeffrey M Stajich, Rita Jewett, Mark A Stacy, Burton L Scott, Jeffery M Vance, William K Scott.
BMC Neurology 2008, 8:6.
Published online 28 March 2008.

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Source: Biomed Central Press release.

Written by: Catharine Paddock, PhD