April is Parkinson’s disease Awareness Month.

SEATTLE — Parkinson’s disease is now considered the fastest-growing neurodegenerative disease in the U.S. 

Researchers are also finding environmental factors — even our drinking water — may play a bigger role than we thought.

Parkinson’s disease usually begins with tremors and muscle stiffness, leading to limited mobility. Those battling the disease may ask: What caused this? And could this have been prevented? The answer isn’t easy.

“It seems like every six minutes we diagnose someone with Parkinson’s in the U.S.,” said Dr. Pravin Khemani, a neurologist at Providence Swedish specializing in movement disorders.

He says older age is the biggest known risk factor for developing Parkinson’s, with cases rising sharply after age 65. 

But when asked about several studies over the years linking environmental pollutants as a risk factor — for example, chemicals that leach into the groundwater, or exposure to certain pesticides — Khemani notes these studies show correlation, not direct causation.

“The neurodegenerative process takes 10 to 20 years to happen. It’s very difficult to do a study for that long and prove causation because people also up and move from one area to the other,” he said.

However, Khemani acknowledges that several studies do show significance. 

A 2018 study out of Eastern Washington found that exposure to certain weed killers — such as glyphosate and paraquat — is associated with a higher risk of premature death from Parkinson’s disease.

“So now we are generating a list of these contaminants that seem to be linked to Parkinson’s. And how do we prove that? We can’t prove that in humans. But in labs, in laboratory studies, animals in animal models, when they’re exposed to these chemicals, they quickly see neurodegeneration, which can be observed under a microscope,” Khemani said.

Khemani adds, however, that patients could look beyond potential risk factors, as lifestyle can be a powerful preventative tool.

“So now we know that exercise, good sleep, good diet, social engagement and cognitive engagement and maintaining a good mood are critical in lowering the risk, but also potentially in improving symptoms of Parkinson’s,” he said.