The Relationship between Long-Term Air Pollution Exposure and Cognition in Older Adults

Abstract

BACKGROUND AND AIM: Accumulation of evidence has raised concern regarding the harmful effect of air pollution on cognitive function, but results are diverging. We aimed to investigate whether long-term exposure to air pollutants may have an adverse effect on cognitive function in older adults residing in an urban area. METHODS: Data were obtained from the Swedish National Study on Aging and Care in Kungsholmen (SNAC-K). Cognitive impairment, no dementia (CIND) was assessed by a comprehensive neuropsychological battery (scoring ≥1.5 standard deviations below age‐specific means on ≥1 cognitive domain). We assessed long-term residential exposure to particulate matters (PM2.5 and PM10) and nitrogen oxides (NOx) with dispersion modeling. The association with CIND was estimated using Cox proportional hazards models with time-varying air pollution exposure. We further estimated the effect of long-term air pollution exposure on the progression of CIND to dementia. RESULTS:Among 2499 cognitively intact participants, 351 individuals developed CIND during the 12-year follow-up. A 1-μg/m³ increment in PM2.5 exposure was associated with a 63% increased risk of CIND incidence (HR=1.63, 95%CI: 1.44-1.86). Weaker associations were found for PM10 (HR=1.06, 95%CI: 1.01-1.11) and NOx (HR=1.01, 95%CI: 1.00-1.02). Among those with CIND at baseline (n=607), 118 participants developed dementia during follow-up. Moreover, PM2.5 exposure might increase the risk of progression from CIND to dementia in individuals with prevalent CIND at baseline (HR=1.24, 95%CI: 0.88-1.74). CONCLUSIONS:We found suggestive evidence of an association between long-term exposure to ambient air pollutants and incidence of CIND and its progression to dementia in older adults. Further research should focus more on the underlying mechanisms. KEYWORDS: Long-term exposure, Neurodegenerative outcomes, Traffic-related