Exploring Wildfire Smoke Exposure and Risk of Dementia in an Older Patient Population: Joan A. Casey, PhD & Holly Elser, MD, PhD, MPH

WATCH TIME: 7 minutes

"For every one unit increase in the concentration of wildfire PM 2.5 over a 3-year average window, there was a roughly 21% increase in the odds of a new dementia diagnosis."

Previous studies have shown an association between long-term exposure to ambient air pollution, including fine particulate matter less than 2.5μm in diameter (PM2.5), and incident dementia. In a new retrospective open cohort study, results suggested that long-term exposure to PM2.5, both wildfire and non-wildfire, may be an important risk factor for dementia.¹ In the study, investigators explored this association among Kaiser Permanente Southern California patients aged at least 60 years between 2009 and 2019 in California. At baseline, the study participants were dementia-free. Authors identified incident dementia in the electronic health record by utilizing the International Classification of Diseases 9 and 10 codes.

Researchers had estimations for rolling 3-year average concentrations of wildfire and non-wildfire PM2.5 assigned to each patient based on census tract of residence, which they updated quarterly. Investigators then used pooled logistic regression to predict the odds of dementia diagnosis associated with a one μg/m3 increase in the 3-year average of wildfire and non-wildfire PM2.5. All of the models used in the study included fixed effects for calendar year and were adjusted for age, sex, race and ethnicity, marital status, smoking status, Charlson Comorbidity Index (minus dementia), and census tract poverty and population density.

Among 1,227,241 participants, authors reported that approximately half were women (53%) and were married (54%). Additionally, a majority of patients self-identified as non-Hispanic White (49%) or Hispanic (26%). During the study, the mean wildfire PM2.5 concentration was 0.09 (IQR, 9.6–12.4). Following adjustment for covariates, the odds of dementia diagnosis were 10% higher for every 1 μg/m3 higher 3-year average wildfire PM2.5 concentration (OR, 1.10; 95%CI, 0.96-1.25). Notably, the odds of dementia diagnosis were 1 higher for every 1 μg/m3 higher 3-year average exposure (OR = 1.01; 95%CI, 1.00-1.01) for non-wildfire PM2.5.

These results were presented at the 2024 Alzheimer’s Association International Conference, July 28 to August 1, in Philadelphia, Pennsylvania, by lead author Holly Elser, MD, PhD, MPH, neurology resident at the Hospital of the University of Pennsylvania, and senior author Joan A. Casey, PhD, assistant professor in the department of environmental and occupational health sciences at the University of Washington. Prior to the meeting, the duo sat down with NeurologyLive^® in an interview to discuss how wildfire PM 2.5 compared with non-wildfire PM 2.5 in terms of its impact on dementia risk. Elser and Casey also talked about steps that individuals can take to mitigate the risk of dementia associated with poor air quality. Furthermore, the 2 experts spoke about how health systems might adapt to address the increased burden of disease associated with wildfire events.

Click here for more coverage of AAIC 2024.

REFERENCES
1. Elser H, et al. Long-term Wildfire Smoke Exposure and Incident Dementia in a Large California Cohort. Presented at: 2024 Alzheimer’s Association International Conference; July 18 to August 1; Philadelphia, Pennsylvania. Abstract 86179.