• Posted February 28, 2024

Pesticides Linked to Parkinson's Cases in Midwest, Western U.S.

Pesticides and herbicides used in farming appear to increase people's risk of Parkinson's disease, a new, preliminary study finds.

People exposed to pesticides and herbicides are 25% to 36% more likely to develop Parkinson's, according to a study to be presented at the American Academy of Neurology's upcoming annual meeting in April.

The Parkinson's risk was specifically higher in the Rocky Mountains and Great Plains region of the country, researchers said.

“Our methods enabled us to identify parts of the nation where there was a relationship between most pesticides and Parkinson's disease and subsequently pinpoint where the relationship was strongest, so we could explore specific pesticides in that region,” said researcher Brittany Krzyzanowski of the Barrow Neurological Institute in Phoenix.

The region where farm chemicals are most strongly linked to Parkinson's includes parts of Colorado, Idaho, Kansas, Montana, Nebraska, Nevada, New Mexico, North Dakota, Oklahoma, South Dakota, Texas, Utah and Wyoming.

Parkinson's disease is a progressive degenerative disease of the nervous system. Patients become less and less able to control their body, suffering from tremors, leg stiffness and gait and balance problems.

For the study, researchers reviewed records of 21.5 million people enrolled in Medicare in 2009 to determine the rate of Parkinson's disease in various parts of the country.

The team then looked for a possible relationship between those rates of Parkinson's and the use of 65 different pesticides.

“In the Rocky Mountain and Great Plains region, we identified 14 pesticides associated with Parkinson's disease,” Krzyzanowski said in a meeting news release.

The pesticides and herbicides simanzine, atrazine and lindane had the strongest relationship with Parkinson's disease, researchers found.

People living in counties with the highest farm use of the herbicide simanzine were 36% more likely to have Parkinson's than those living in counties with the lowest use, results show.

The herbicide atrazine was associated with a 31% greater likelihood of Parkinson's in counties with the heaviest use, and the insecticide lindane with a 25% greater risk.

The risk remained elevated even after researchers adjusted for other risk factors for Parkinson's, like air pollution exposure.

“It's concerning that previous studies have identified other pesticides and herbicides as potential risk factors for Parkinson's, and there are hundreds of pesticides that have not yet been studied for any relationship to the disease,” Krzyzanowski said.

“Much more research is needed to determine these relationships and hopefully to inspire others to take steps to lower the risk of disease by reducing the levels of these pesticides,” she added.

Because the findings were presented at a medical meeting, they should be considered preliminary until published in a peer-reviewed journal.

More information

The Parkinson's Foundation has more on Parkinson's disease.

SOURCE: American Academy of Neurology, news release, Feb. 27, 2024