Long-Term Air Pollution Exposure Increases Dementia Risk

Earlier this week, researchers in JAMA Internal Medicine published an investigation analyzing the impacts of air pollution from varying sources on dementia risk in the United States. Researchers determined long-term exposure to fine particulate matter (PM₂.₅) increases dementia incidence.

In recent years, researchers have explored the detrimental effects of air pollution, specifically the impacts of particulate matter. These particles, comprised of nitrates, carbons, sulfates, or mineral dust, have been linked to adverse health impacts, including altered lung function and development, cardiovascular or respiratory disease, and some cancers.

In particular, PM₂.₅ has been associated with arterial calcification and impaired blood vessel function. Exposure to PM₂.₅ in the womb can yield lower birth weights and alter brain development or function.

"As we experience the effects of air pollution from wildfires and other emissions locally and internationally, these findings contribute to the strong evidence needed to best inform health and policy decisions," said Richard J. Hodes, MD, director National Institute on Aging (NIA), part of NIH, in the NIH press release. "These results are an example of effectively using federally funded research data to help address critical health risks."

Knowing the detrimental impacts of particulate matter and its effects on cognition, researchers conducted this population-based cohort study using data from the Environmental Predictors of Cognitive Health and Aging study.

That study collected survey results from patients in the Health and Retirement study between January 1, 1998, and December 31, 2016. Researchers in JAMA Internal Medicine analyzed results between January 31, 2022, and May 1, 2022.

Alongside data from over 27,000 patients, the investigators used insight from the Environmental Protection Agency (EPA) and other studies or variables to estimate PM₂.₅ exposure. Nine distinct emission sources were identified: agriculture, road traffic, non-road traffic, coal combustion for energy production, other energy production, coal combustion for industry, other industry, open fires, and windblown dust.

Approximately 15% of patients in the study developed dementia, with most dementia incidence found in communities with greater PM2.5 levels. Other factors associated with increased dementia risk included being part of a minority race/ethnicity, lower economic status, and less formal education.

After adjusting for many factors, the study leaders estimated that PM₂.₅ exposure increased dementia incidence by 8%. The most significant correlation between dementia risk and PM₂.₅ exposure was from agricultural and wildfire emissions, with a 13% and 5% increased risk, respectively.

"This level of specificity is new and useful," said Jonathan W. King, PhD, NIA project scientist for HRS. "As NIA continues to conduct and fund studies on risk factors for dementia, these results will help inform future research and, potentially, policy interventions."