Air Pollution Linked to PD, With Some Parts of US More Affected Than Others

Living in areas of the United States with higher levels of air pollution is associated with an increased risk of Parkinson disease, according to preliminary study results.

The study will be presented at the American Academy of Neurology’s 75th Annual Meeting happening April 22 to 27 in Boston.

Other research has indicated links between pollution and neurological diseases such as PD and also dementia.

The current study looked at fine particulate matter, PM_2.5, which is less than 2.5 microns in diameter. Fine particles come from motor vehicle exhaust, the burning of fuels by power plants and other industries and forest and grass fires.

The researchers used geographic methods to examine PD rates across the the country and then compared those rates to regional levels of air pollution.

Inidividuals exposed to the highest levels of fine particulate matter had an increased risk of PC compared with people exposed to the lowest levels.

Using a database of more than 22.5 million Medicare beneficiaries in 2009, the researchers identified 83,674 people with PD.

Locations of study participants were mapped across the United States and researchers calculated PD rates for various regions.

Average air pollution exposure levels were calculated at the ZIP code and county level using an air pollution data source on average annual concentrations of fine particulate matter.

Researchers then divided participants 4 groups based on average exposure to air pollution. People in the highest exposure group had an average annual exposure of 19 micrograms per cubic meter (µg/m3) of fine particulate matter. People in the lowest exposure group had an average annual exposure of 5 µg/m3.

Researchers found the strongest association between air pollution and PD in the Rocky Mountain region, which includes Lake County, Colorado, which is southwest of Denver, and its surrounding counties. The risk for PD in those counties increased by 16% when moving up from one level of fine particulate matter exposure to the next level.

In the highest exposure group, 434 new Parkinson’s disease cases developed per every 100,000 people compared with 359 cases in the lowest exposure group.

After adjusting for other factors that could affect PD risk, such as age, smoking, and use of medical care, researchers found an association between PD and average annual exposure to fine particulate matter, with people in the highest exposure group having a 25% increased risk of Parkinson’s disease compared with people in the lowest exposure group.

For geographic analysis, researchers divided fine particulate matter exposure into 10 levels.

Air pollution was also associated with higher rates of PD in the Mississippi-Ohio River Valley hot spot, which includes Tennessee and Kentucky, but the association was weaker in these areas, with a 4% increase in risk when moving up one level of fine particulate matter exposure to the next

“Finding a relatively weaker association where we have some of the highest Parkinson’s disease risks and fine particulate matter levels in the nation is consistent with the threshold effect we observed in our data,” said author Brittany Krzyzanowski, PhD, of the Barrow Neurological Institute in Phoenix, Arizona, in a statement. “In the Mississippi-Ohio River Valley, for example, Parkinson’s disease risk increases with increasing air pollution exposure until about 15 µg/m3 of fine particulate matter, where Parkinson’s disease risk seems to plateau.”

“By mapping nationwide levels of Parkinson’s disease and linking them to air pollution, we hope to create a greater understanding of the regional risks and inspire leaders to take steps to lower risk of disease by reducing levels of air pollution,” she added.

A limitation of the study was that it focuses on fine particulate matter, which contains a variety of airborne pollutants, some of which may be more toxic than others. Air pollution is also associated with a variety of other health risks, including dementia, that might diminish the likelihood of PD diagnosis and this may explain the relatively weaker association between PD and particulate matter in the Mississippi-Ohio River Valley.

Reference

Study finds air pollution exposure linked to Parkinson’s risk, identifies U.S. hot spot. American Academy of Neurology. February 23, 2023. Accessed February 23, 2023. https://www.eurekalert.org/news-releases/980433