Pesticide exposure increases the risk of Parkinson’s disease 

A preliminary study has established a significant link between pesticide exposure and the incidence of Parkinson’s disease in the Rocky Mountain and Great Plains regions of the United States. 

The research was led by Dr. Brittany Krzyzanowski of the Barrow Neurological Institute in Phoenix, Arizona. The results highlight the complex interplay between environmental factors and neurological health.

Regional levels of pesticide use

“We used geographic methods to examine the rates of Parkinson’s disease across the United States and compared those rates to regional levels of pesticide and herbicide use,” said Dr. Krzyzanowski.

“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.” 

“In the Rocky Mountain and Great Plains region, we identified 14 pesticides associated with Parkinson’s disease.”

Focus of the study

Dr. Krzyzanowski said the most affected region includes parts of Colorado, Idaho, Kansas, Montana, Nebraska, Nevada, New Mexico, North Dakota, Oklahoma, South Dakota, Texas, Utah and Wyoming. This part of the country emerged as a focal point due to its alarming association with Parkinson’s disease.

For the investigation, Dr. Krzyzanowski and her team analyzed the health records of 21.5 million individuals enrolled in Medicare in 2009. The goal was to compare the regional Parkinson’s disease rates with the use of 65 different pesticides. 

Clear and concerning trend

The findings are alarming: pesticides and herbicides such as simazine, atrazine, and lindane were strongly linked to increased rates of Parkinson’s disease. 

Simazine

In particular, the study revealed that residents in counties with the highest levels of simazine application were 36% more likely to develop Parkinson’s disease compared to those in areas with minimal exposure. 

According to the results, in the counties with the highest exposure to simazine, 411 new Parkinson’s disease cases developed per every 100,000 people. This is significantly higher than the rate of 380 cases in the counties with the lowest exposure.

Atrazine

The results also showed that individuals exposed to the highest amount of the herbicide atrazine were 31% more likely to have Parkinson’s disease compared to those with the lowest exposure. 

In the counties with the highest exposure to atrazine, 475 new Parkinson’s disease cases developed per every 100,000 people compared to 398 cases in the counties with the lowest exposure.

Lindane

Furthermore, individuals with the greatest exposure to the insecticide lindane were 25% more likely to develop the disease. 

Across counties with the highest exposure to lindane, 386 new Parkinson’s disease cases developed per every 100,000 people compared to 349 cases in the counties with the lowest exposure.

Further research is urgently needed 

The researchers said that even after they adjusted for other factors that could affect the risk of Parkinson’s disease, such as air pollution exposure, the results remained the same.

“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,” said Dr. Krzyzanowski. 

“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.”

The study was supported by Michael J. Fox Foundation for Parkinson’s Research. The results will be presented at the 76th Annual Meeting of the American Academy of Neurology, scheduled from April 13–18, 2024.

Parkinson’s disease

Parkinson’s disease is a progressive neurological disorder that primarily affects movement, leading to symptoms that worsen over time. 

The disease is caused by the degeneration and loss of neurons in the brain, particularly in an area called the substantia nigra, which is crucial for controlling movements. These neurons produce dopamine, a neurotransmitter that plays a key role in sending messages to the part of the brain that controls movement and coordination. 

As Parkinson’s disease progresses, the amount of dopamine produced in the brain decreases, leaving a person unable to control movement normally.

Symptoms

The symptoms of Parkinson’s disease are varied and can include tremors (shaking), bradykinesia (slowness of movement), limb rigidity, and problems with balance and coordination. These symptoms can lead to difficulty with walking, talking, and completing simple tasks. 

Parkinson’s can also cause non-motor symptoms, including sleep disturbances, mood disorders, cognitive impairment, and autonomic dysfunction, which can affect blood pressure, bowel and bladder function, and sexual performance.

Possible causes

The exact cause of Parkinson’s disease is unknown, but it’s believed to be a combination of genetic and environmental factors. 

Exposure to certain toxins, such as pesticides, has been linked to an increased risk of developing the disease, and some genetic mutations have been identified that contribute to its development, though these are less common.

Treatments

There is currently no cure for Parkinson’s disease, but treatments are available to help manage its symptoms. Medication therapy, most notably levodopa combined with carbidopa, is used to increase dopamine levels in the brain or mimic its actions, helping to control motor symptoms. 

Other treatments can include deep brain stimulation (DBS), physical therapy, and occupational therapy, aimed at improving quality of life.

Ongoing research 

Research into Parkinson’s disease is ongoing, with scientists looking for better ways to treat the disease, manage its symptoms more effectively, and ultimately find a cure. 

Experts like Dr. Krzyzanowski are studying the potential links between pesticide exposure and other environmental factors and the development of Parkinson’s disease. This may ultimately lead to the development of new treatment options that target the underlying causes of the disease rather than just its symptoms.

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