MONDAY, Feb. 23, 2026 (HealthDay News) -- Fine particulate matter (PM2.5) exposure is directly associated with an increased risk for Alzheimer disease (AD), according to a study published online Feb. 17 in PLOS Medicine.
Yanling Deng, from Rollins School of Public Health at Emory University in Atlanta, and colleagues examined whether common comorbidities such as hypertension, stroke, and depression modify the association between PM2.5 exposure and incident AD in a nationwide cohort study including 27.8 million U.S. Medicare beneficiaries aged 65 years and older.
The researchers identified about 3.0 million incident AD cases. In the overall population, PM2.5 exposure (five-year moving average prior to AD onset) was associated with an increased risk for AD (hazard ratio [HR] per interquartile range [IQR] increase, 1.085). In individuals with stroke, the association was slightly stronger (HR per IQR increase, 1.105); little effect modification was seen for hypertension or depression. Higher risks for hypertension, depression, and stroke were seen in association with PM2.5 exposure, all of which were linked to increased AD risk. However, minimal mediation effects were seen, with 1.6, 4.2, and 2.1 percent of the association between PM2.5 and incident AD mediated by hypertension, stroke, and depression, respectively.
"Our findings suggest that reducing air pollution could benefit cognitive health broadly across older adults, while targeted interventions may be especially important for those with cerebrovascular disease or multiple chronic conditions," the authors write.