Daily Exceedance of World Health Organization Air Pollutant Guidelines and Cognitive Aging.

Abstract

Importance: Long-term exposure to higher average air pollutant concentrations is associated with poorer cognitive health, but annual averages can obscure substantial differences in dayto-day exposure. Whether recurrent high pollution days are associated with long-term cognitive aging trajectories among people with similar overall air pollution exposure is unclear.

Objective: To determine whether the annual number of days exceeding World Health Organization daily guideline values for nitrogen dioxide (NO₂) and particulate matter (PM_2.5 and PM₁₀) is associated with subsequent cognitive decline after accounting for annual mean air pollutant exposure.

Design: Prospective cohort study using data from waves 1-10 (2002-03 to 2021-23) of the English Longitudinal Study of Ageing.

Setting: Population-based cohort of community-dwelling adults in England.

Participants: 12,235 adults aged 50+ years at analytic baseline.

Exposures: Number of days exceeding World Health Organization daily guideline values ('exceedance days') for NO₂, PM_2.5, and PM₁₀, derived from residence-linked environmental estimates during the calendar year preceding the analytic baseline.

Main outcomes and measures: Baseline cognitive performance and model-estimated 14-year cognitive decline (corresponding to the 75th percentile of follow-up duration) in episodic memory and verbal fluency.

Results: Exceedance days were not associated with baseline memory or verbal fluency after adjustment for annual mean air pollutant exposure. More NO₂ exceedance days were associated with faster cognitive decline: comparing the 75th percentile with the median of NO₂ exceedance days, the difference in 14-year decline was -0.09 SD (95% CI, -0.17 to -0.01; p = 0.02) for memory and -0.10 SD (95% CI, -0.19 to 0.00; p = 0.04) for fluency. PM_2.5 and PM₁₀ exceedance days were not associated with cognitive decline.

Conclusions and relevance: In this cohort study of older adults, a higher number of NO₂ exceedance days was associated with faster subsequent cognitive decline after adjustment for annual mean air pollutant exposure. This suggests that daily exposure to high NO₂ concentrations may be related to accelerated cognitive aging even when offset by lower exposure on other days, potentially providing a new rationale for identifying and prioritizing areas with recurrent high NO₂ exposure and the local emission sources contributing to it.