Wildfire Smoke Exposure and Incident Dementia

Area of Science:

• Environmental Health
• Neuroscience
• Epidemiology

Background:

• Long-term exposure to fine particulate matter (PM2.5) is a known risk factor for dementia.
• The specific impact of wildfire-generated PM2.5 on dementia risk remains less understood, despite its increasing prevalence.

Purpose of the Study:

• To investigate the association between long-term exposure to wildfire and non-wildfire PM2.5 and the risk of developing dementia.
• To assess potential disparities in dementia risk related to PM2.5 exposure.

Main Methods:

• An open cohort study utilized electronic health record data from 1.22 million Kaiser Permanente Southern California members (aged 60+) from 2008-2019.
• Exposure was assessed using 3-year rolling mean estimates of wildfire and non-wildfire PM2.5 at the census tract level.
• Incident dementia was identified via diagnostic codes, with analyses adjusted for demographic and socioeconomic factors.

Main Results:

• A 1-μg/m3 increase in 3-year mean wildfire PM2.5 exposure was linked to an 18% higher odds of dementia diagnosis (OR, 1.18).
• In contrast, a similar increase in non-wildfire PM2.5 exposure was associated with a 1% increase in dementia odds (OR, 1.01).
• Stronger associations between wildfire PM2.5 and dementia were observed in younger individuals (<75), racial/ethnic minority groups, and those in high-poverty areas.

Conclusions:

• Long-term exposure to both wildfire and non-wildfire PM2.5 is associated with increased odds of dementia diagnoses.
• Climate change-driven increases in wildfire PM2.5 may exacerbate dementia incidence and health inequities.
• Interventions targeting wildfire PM2.5 reduction could be crucial for dementia prevention efforts and addressing health disparities.