Long-Term Exposure to Wildfire Smoke and Dementia Risk: What’s the Link?

The risk for dementia may significantly increase with extended exposure to fine particulate matter (PM) less than 2.5μm from wildfire or other non-wildfire sources, according to study results presented at the Alzheimer’s Association International Conference (AAIC) 2024 Annual Meeting, held in Philadelphia, Pennsylvania, from July 28 to August 1.

The increasing intensity of wildfire seasons driven by climate change may elevate the risk for dementia and other diseases linked to PM_2.5 exposure, further emphasizing the established connections between long-term air pollution and diseases like dementia, heart disease, and asthma.

Researchers conducted a retrospective cohort study to determine the relationship between prolonged exposure to wildfire and non-wildfire PM_2.5 and the subsequent risk for dementia.

The primary outcome of interest was the incidence of dementia.

Researchers also assessed demographics, smoking status, health comorbidity, poverty level, and population density.

The researchers collected data from electronic health records of Kaiser Permanente Southern California members between 2009 and 2019. Individuals were eligible for inclusion if they were aged 60 and older and had no previous dementia diagnosis (N=1,227,241; women, 53%; non-Hispanic White, 49%).

The average PM_2.5 concentration resulting from wildfires was measured at 0.09 μg/m³.

A 1 μg/m³ increase in the 3-year average of PM_2.5 from wildfires was associated with a 10% higher likelihood of developing dementia (odds ratio [OR], 1.10; 95% CI, 0.96-1.25). In contrast, a similar 1 μg/m³ increase in the 3-year average of non-wildfire PM_2.5 was linked to a 1% rise in the risk of developing dementia (OR, 1.01; 95% CI, 1.00-1.01).

“Long-term exposure to PM_2.5, both wildfire and non-wildfire, may be an important risk factor for dementia,” the researchers concluded.