Wildfire Smoke Exposure Significantly Increases Dementia Risk

Individuals exposed to wildfire smoke were found to have an increased likelihood of developing dementia. While other forms of ambient air pollution were also found to be harmful for brain health, wildfire fine particulate matter (PM_2.5) posed a significantly higher risk for the diagnosis of dementia, even at lower levels of exposure. The study findings were reported at the 2024 meeting of the Alzheimer’s Association International Conference (AAIC).

During the 10-year study period from 2009 to 2019, researchers examined the health records of 1,227,241 California residents aged ≥60 years from diverse socioeconomic backgrounds. All participants were free of a dementia diagnosis at baseline. Once total levels of PM_2.5 pollution were determined, the researchers used air quality monitoring data, satellite imagery and machine learning techniques to separate wildfire PM_2.5 from other sources of PM_2.5. Individual participant exposure was determined by census tract of residence.

• Wildfire PM_2.5 exposure increased the risk of dementia diagnosis by 10% for every increase of 1 μg/m3 higher 3-year average PM_2.5 concentration (OR, 1.10; 95%CI, .96 to 1.25).
• Non-wildfire PM_2.5 exposure increased the risk of dementia diagnosis by 3% for every increase of 3 μg/m3 higher 3-year average PM_2.5 concentration (OR, 1.01; 95%CI, 1.00 to 1.01).

“The findings appeared most pronounced among individuals from racially and ethnically minoritized groups and in high poverty areas,” said Joan A. Casey, PhD, Senior Study Author and Assistant Professor in the Department of Environmental and Occupational Health Sciences at the University of Washington, Seattle. “These findings underscore that clinical and health policies seeking to prevent dementia-associated disparities should include efforts to reduce exposure to long-term wildfire and non-wildfire PM2.5.”