A study presented at the Alzheimer's Association International Conference (AAIC) 2024 has found that exposure to wildfire smoke may pose a greater risk for dementia than other sources of air pollution. The study, which followed more than 1.2 million southern Californians over a decade, suggests that the microscopic particulate matter (PM2.5) produced by wildfires is particularly hazardous to brain health.

Researchers from the University of Pennsylvania and the University of Washington analyzed the health records of 1,227,241 Kaiser Permanente southern California members aged 60 years or older between 2009 and 2019. None of the participants had been diagnosed with dementia at the beginning of the study. The team estimated each participant's exposure to PM2.5 from various sources, including wildfires, using air quality monitoring data, satellite imagery, and machine-learning techniques.

The study found that for every 1 μg/m3 increase in the 3-year average wildfire PM2.5 exposure, there was a 21% increase in the odds of dementia diagnosis. In comparison, for every 3 μg/m3 increase in the 3-year average of nonwildfire PM2.5 exposure, there was only a 3% increased risk of dementia diagnosis.

Holly Elser, MD, PhD, the study's first author and a neurology resident at the Hospital of the University of Pennsylvania, noted that wildfire smoke may be more hazardous than other pollutants due to several factors—including higher production temperatures, greater concentrations of toxic chemicals, and smaller particle diameters—compared to PM2.5 from other sources.

Heightened risks were most pronounced among individuals from racial and ethnic minority groups and those living in high-poverty areas. Joan A. Casey, PhD, senior author of the study and assistant professor at the University of Washington, emphasized that clinical and health policies aimed at preventing dementia-associated disparities should include efforts to reduce exposure to long-term wildfire and nonwildfire PM2.5.

To minimize the risk of exposure, the researchers recommend updating home air filtration systems, staying inside when the air quality is unhealthy (Air Quality Index of 100 or higher), and wearing an N95 mask when outdoors during such conditions.

As wildfires become more frequent and intense due to climate change, understanding the link between wildfire smoke and brain health is crucial. Further research is needed to determine the exact mechanisms by which wildfire PM2.5 may increase the risk of dementia.