High nitrogen dioxide days linked to faster cognitive decline
Comparing the 75th percentile with the median of nitrogen dioxide exceedance days, 14-year decline was -0.09 SD for memory and -0.10 SD for fluency.
medRxiv
In a cohort of 12,235 community-dwelling adults in England aged 50 and older, researchers examined whether days exceeding World Health Organization air quality guidelines were linked to cognitive aging. Using data from the English Longitudinal Study of Ageing, the authors tracked episodic memory and verbal fluency over a median follow-up of 8.3 years. Daily exposure to nitrogen dioxide (NO2), PM2.5, and PM10 was estimated at residential locations during the calendar year before baseline.
Exceedance days showed no association with baseline cognitive performance after adjusting for annual mean pollutant levels. However, a higher number of NO2 exceedance days was associated with faster 14-year decline in both memory and verbal fluency. Days exceeding guidelines for PM2.5 or PM10 were not associated with cognitive decline.
Why it matters
The findings suggest that recurrent short-term exposure to high pollution levels may accelerate cognitive aging independently of annual average exposure. This highlights how intermittent environmental insults could shape brain health trajectories across late life.
Caveats
The study is an observational preprint that has not undergone peer review. In addition, air pollution was modeled from residential addresses rather than measured using personal exposure monitors, which does not account for indoor air quality or participant mobility.
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medRxiv · 29 Sep 2026 · Preprint, not peer-reviewed