In the Rocky Mountain and Great Plains region of the United States, pesticide and herbicide use at the county level is associated with increased risk of Parkinson disease (PD) in residents. Researchers plan to present their findings at the American Academy of Neurology annual meeting in Denver, Colorado, and online in April.

The study analyzed rates of PD among 21.5 million Medicare beneficiaries across the United States and compared them with regional levels of pesticide and herbicide use in farming.

“Our methods enabled us to identify parts of the nation where there was a relationship between most pesticides and PD and subsequently pinpoint where the relationship was strongest so we could explore specific pesticides in that region,” said study author Brittany Krzyzanowski, PhD, of the Barrow Neurological Institute in Phoenix, Arizona. “In the Rocky Mountain and Great Plains region, we identified 14 pesticides associated with PD.”

>>NEWS: Constant Stress Response Causes Cell Death in Neurodegenerative Disease

Among 65 pesticides and herbicides investigated in the region — which spans parts of Colorado, Idaho, Kansas, Montana, Nebraska, Nevada, New Mexico, North Dakota, Oklahoma, South Dakota, Texas, Utah, and Wyoming — the strongest associations involved the use of simazine, atrazine, and lindane, according to the study.

When researchers divided the region’s counties into 10 groups based on pesticide and herbicide use, people in counties with the highest use of the herbicide simazine were 36% more likely to have PD compared with those in counties with the lowest use. Counties with the highest simazine use had 411 new PD diagnoses per 100,000 people compared with 380 in the counties with the lowest use.

People in counties with the highest use of the herbicide atrazine were 31% more likely to have PD, and those in counties with the highest use of the insecticide lindane were 25% more likely to have PD, compared with people in counties with the lowest levels of use.

Per 100,000 people, counties with the highest atrazine use had 475 new PD diagnoses compared with 398 in counties with the lowest use. For lindane, counties with the highest use had 386 new PD diagnoses per 100,000 people compared with 349 in counties with the lowest use.

Adjustment for confounding factors, including exposure to air pollution, did not affect the results.

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

Reference

Study finds pesticide use linked to Parkinson’s in rocky mountain, great plains region. News release. American Academy of Neurology; February 27, 2024. Accessed March 15, 2024.