Parkinson's disease nerve cells, illustration
Credit: Kateryna Kon / Science Photo Library

Researchers at the Barrow Neurological Institute have found that people living in regions that have median levels of air pollution have a 56 percent greater risk of developing Parkinson’s disease compared with those who live in areas with the lowest levels of air pollution. The study, which was conducted to look for patterns of Parkinson’s disease across the U.S. and region-specific associations with fine particulate matter also found that the relationship between development of the disease and air pollution varies by region.

“Previous studies have shown fine particulate matter to cause inflammation in the brain, a known mechanism by which Parkinson’s disease could develop,” said Brittany Krzyzanowski, PhD, a researcher at Barrow Neurological Institute who led the study published in the journal Neurology. “Using state-of-the-art geospatial analytical techniques, we were, for the first time, able to confirm a strong nationwide association between incident Parkinson’s disease and fine particulate matter in the U.S.”

For their population-based geographic study, the investigators used a Medicare dataset that contained information from 22 million people, of which 90,000 were diagnosed with Parkinson’s diseases. The records of those with Parkinson’s disease were then tracked and grouped to their neighborhoods where they lived, which allowed the researchers to determine disease incidence rates in different regions. The team adjusted their findings to allow for other known risk factors that included age, sex, race, smoking history, and healthcare utilization rates to then identify each person’s previous exposure to fine particulate matter and risk of developing Parkinson’s disease.

Some regions in the U.S. were identified as hotspots of Parkinson’s disease development including the Mississippi-Ohio River Valley, central North Dakota, parts of Texas, Kansas, eastern Michigan and the tip of Florida. Conversely, people who live in the western half of the U.S. were found to have a reduced risk of Parkinson’s disease development compared with the rest of the country.

Krzyzanowski noted that these regional differences may be a result not of the levels of fine particulate matter in the air, but rather the composition of particulate matter, with some regions have fine particulate matter that is more toxic than other areas. While the current study did not analyze the different sources of pollution in different regions, Krzyzanowski noted that the Mississippi-Ohio River Valley has both a highly developed networks of roads, while also containing areas of the country considered part of the “rust belt.”

“This means that the pollution in these areas may contain more combustion particles from traffic and heavy metals from manufacturing which have been linked to cell death in the part of the brain involved in Parkinson’s disease,” she said.

Previous studies have explored the environmental risk factors of Parkinson’s disease, but most have zeroed in on a person’s exposure to pesticides. With the new findings investigators hope their data can be employed to develop new policies to control air pollution that can lower the risk of Parkinson’s disease along with other associated illnesses.

“Population-based geographic studies like this have the potential to reveal important insight into the role of environmental toxins in the development and progression of Parkinson’s, and these same methods can be applied to explore other neurological health outcomes as well,” concluded Krzyzanowski.

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