Days exceeding NO2 guidelines linked to faster cognitive decline
Comparing the 75th percentile with the median of NO2 exceedance days, 14-year cognitive decline was -0.09 SD for memory and -0.10 SD for fluency.
medRxiv
In a prospective cohort study of 12,235 community-dwelling adults aged 50 and older in England, researchers examined whether annual days exceeding World Health Organization air quality guidelines were associated with cognitive aging. Using data from the English Longitudinal Study of Ageing, the authors estimated daily residential exposure to nitrogen dioxide (NO2), PM2.5, and PM10 during the calendar year preceding baseline cognitive assessments.
After adjusting for annual mean pollutant exposures, exceedance days were not linked to baseline memory or verbal fluency. However, a higher number of NO2 exceedance days was associated with faster 14-year cognitive decline in both episodic memory and verbal fluency. Exceedance days for PM2.5 and PM10 showed no association with cognitive decline.
Why it matters
The findings suggest that recurrent daily spikes in ambient NO2 exposure may accelerate cognitive aging trajectories even when annual average pollution levels appear low. This indicates that short-term environmental fluctuations, rather than annual averages alone, could influence late-life neurocognitive decline.
Caveats
The observational design cannot establish causality and relies on modeled residential air pollutant estimates rather than personal exposure monitoring. Exposure was also characterized across a single pre-baseline calendar year, and the report is a preprint that has not yet completed peer review.
The paper
Daily Exceedance of World Health Organization Air Pollutant Guidelines and Cognitive Aging
University College London
medRxiv · 29 Sep 2026 · Preprint, not peer-reviewed