A focus on air pollution
Existing research in examining the etiology of Parkinson’s mainly focused on exposure to pesticides,* Dr. Krzyzanowski explained, and “consists of studies using relatively small populations and low-resolution air pollution data.” Genetics is another possible cause, she noted, but only explains some Parkinson’s disease cases.
“Our work suggests that we should also be looking at air pollution as a contributor in the development of Parkinson’s disease,” she said.
Dr. Ray Dorsey
Ray Dorsey, MD, professor of neurology at the University of Rochester (N.Y.), who was not involved with the study, said that evidence is mounting that “air pollution may be an important causal factor in Parkinson’s and especially Alzheimer’s disease.”
“This study by a well-regarded group of researchers adds epidemiological evidence for that association,” he said. Another strength is that the study was conducted in the United States, as many epidemiological studies evaluating air pollution and Parkinson’s disease have been performed outside the country because of “a dearth of reliable data sources.”
“This study, along with others, suggest that some of the important environmental toxicants tied to brain disease may be inhaled,” Dr. Dorsey said. “The nose may be the front door to the brain.”
Dr. Krzyzanowski said the next step in their research is further examination of different types of air pollution. “Air pollution contains a variety of toxic components which vary from region to region. Understanding the different components in air pollution and how they interact with climate, temperature, and topography could help explain the regional differences we observed.”
One potential limitation in the study is a lag between air pollution exposure and development of Parkinson’s disease, Dr. Dorsey noted.
“Here, it looks like (but I am not certain) that the investigators looked at current air pollution levels and new cases of Parkinson’s. Ideally, for incident cases of Parkinson’s disease, we would want to know historical data on exposure to air pollution,” he said.
Future studies should include prospective evaluation of adults as well as babies and children who have been exposed to both high and low levels of air pollution. That kind of study “would be incredibly valuable for determining the role of an important environmental toxicant in many brain diseases, including stroke, Alzheimer’s, and Parkinson’s,” he said.
Dr. Krzyzanowski and Dr. Dorsey reported no relevant financial disclosures. This study was supported by grants from the Department of Defense, the National Institute of Environmental Health Sciences, and The Michael J. Fox Foundation for Parkinson’s Research.
*Correction, 4/14/23: An earlier version of this article mischaracterized the disease that was the subject of this research.