A contentious new study has found that people who live near golf courses may face a higher risk of Parkinson's disease.

That does not mean that golf courses are directly causing Parkinson's, but the authors of the study, led by Brittany Krzyzanowski of the Barrow Neurological Institute in the US, have a hypothesis. They think that rampant pesticides on fairways and greens may be exposing nearby residents to toxic chemicals via the air and water.

That's a scary prospect, to be sure, but independent experts at the non-profit Parkinson's UK, who were not involved in the current research, have called these suspicions "reductive".

Parkinson's disease is a complex neurological condition without known cause, and in recent years, intense debate has raged over whether certain pesticides may increase the risk of neurodegeneration.

Farmers, for instance, tend to face higher risks of Parkinson's, as do those who live in historically industrial regions. Studies in the lab suggest some pesticides and air pollutants can be toxic to brain cells.

But while human-made chemicals may be a factor in Parkinson's disease, so could genetics. The evidence at this point is not clear-cut.

"Many studies have investigated whether pesticides increase the risk of developing Parkinson's in different populations around the world," says Katherine Fletcher, lead researcher at Parkinson's UK.

"The results have been varied, but overall suggest that exposure to pesticides may increase the risk of the condition. However, the evidence is not strong enough to show that pesticide exposure directly causes Parkinson's."

The newest research from Krzyzanowski and colleagues at the Mayo Clinic, the University of Rochester, and the University of Kansas adds to the debate.

Their population-based study compared 419 Parkinson's cases with 5,113 healthy individuals, matched for sex, age, and demographics.

After adjusting for various neighborhood characteristics, the team found that living within a mile (1.6 kilometers) of a golf course was associated with a 126 percent increased risk of developing Parkinson's, compared to those living more than 6 miles (nearly 10 kilometers) away.

What's more, people living within water service areas containing a golf course were found to have nearly double the odds of developing Parkinson's compared to those living in golf-free areas.

These correlations have led Krzyzanowski and colleagues to argue that golf courses are a possible risk factor for Parkinson's disease, and that pesticides in the air and in the groundwater may contribute to that risk.

"Public health policies to reduce the risk of groundwater contamination and airborne exposure from pesticides on golf courses may help reduce risk of Parkinson's disease in nearby neighborhoods," argue Krzyzanowski and her team.

But Fletcher and her colleague, David Dexter, at Parkinson's UK are unconvinced. The new study never tested for groundwater contamination near golf courses, or pollutants in the air, nor did the researchers properly control for other sources of urban air pollution, like that kicked up by road traffic.

What's more, groundwater data on pesticides around golf courses is limited, and a 2024 study found that airborne pesticides are of "limited concern" to golfers, even after playing an 18-hole course purposefully sprayed with chemicals.

"Parkinson's starts in the brain 10 to 15 years before diagnosis, and the study didn't only use subjects who permanently lived in the area," adds Dexter in an independent comment.

"This would not only affect participants' exposure, but also suggests their Parkinson's could have started before they moved around a golf course."

The current research elevates recent concerns around pesticides, but it is hardly a hole-in-one. Researchers will need to take quite a few more swings to prove that pesticides from golf courses are leaching into groundwater and raising the risk of Parkinson's for those living nearby.

The study was published in JAMA Network Open.