Exposure to ambient fine particulate matter (PM2.5) is associated with cardiovascular and inflammatory pathways implicated in neurodegeneration. However, epidemiologic findings linking PM2.5 exposure to dementia incidence remain heterogeneous. We conducted a systematic review and meta-analysis of existing cohort studies evaluating the association between PM2.5 exposure and incident dementia. A literature search yielded 909 records, of which 15 cohort studies, including approximately 65 million participants in Europe, Asia, and North America, were included in the meta-analysis. Hazard ratios were standardized to a 1 μg/m3 increase in PM2.5 exposure using logarithmic transformation. Effect estimates were then pooled using a random-effects model. Long-term PM2.5 exposure was associated with an increased risk of incident dementia (pooled HR 1.04, 95% confidence interval 1.01-1.06). Substantial heterogeneity was observed across studies (I2 = 88.3%). These findings support growing evidence that chronic exposure to fine particulate air pollution may contribute to the development of dementia and highlight air pollution as a potentially modifiable environmental risk factor for neurodegenerative disease.
Rocheeld et al. (2026) studied this question.