Air pollution and cognitive outcomes in older adults: a systematic review.

The rising prevalence of cognitive decline and dementia imposes substantial burdens on individuals, families, and society. Air pollution has increasingly been linked to adverse cognitive outcomes, but findings vary across pollutants, study designs, and exposure-assessment methods. This review summarizes epidemiological evidence on ambient air pollution and cognitive outcomes among older adults, identifies research gaps, and outlines priorities for future investigation. PubMed was searched through February 2025 for peer-reviewed, English-language observational studies published from January 2000 onward that examined ambient air pollution and cognitive outcomes among adults aged 50 years and older. A total of 36 studies met the inclusion criteria. Fine particulate matter (PM2.5) was the most frequently studied pollutant, and most studies reported associations between higher PM2.5 exposure and poorer global or domain-specific cognitive function, faster cognitive decline, or increased risk of cognitive impairment and dementia. Evidence for other pollutants generally suggested adverse associations, although ozone (O3) findings were the most inconsistent. Differences in exposure assessment methods, cognitive assessment, study designs, confounding control, and population susceptibility likely contributed to heterogeneity. Overall, the accumulated evidence suggests that long-term ambient air pollution exposures may contribute to poorer cognitive outcomes in later life. These findings underscore the importance of strengthening air quality standards to protect brain health and developing targeted interventions for vulnerable older populations.