Long-Term Exposure to Air Pollutants and Cognitive Function in Taiwanese Community-Dwelling Older Adults: A Four-Year Cohort Study

Background: Previous studies have assessed limited cognitive domains with relatively short exposure to air pollutants, and studies in Asia are limited. Objective: This study aims to explore the association between long-term exposure to air pollutants and cognition in community-dwelling older adults. Methods: This four-year prospective cohort study recruited 605 older adults at baseline (2011–2013) and 360 participants remained at four-year follow-up. Global and domain-specific cognition were assessed biennially. Data on PM2.5 (particulate matter≤2.5μm diameter, 2005–2015), PM10 (1993–2015), and nitrogen dioxide (NO2, 1993–2015) were obtained from Taiwan Environmental Protection Administration (TEPA). Bayesian Maximum Entropy was utilized to estimate the spatiotemporal distribution of levels of these pollutants. Results: Exposure to high-level PM2.5 (>29.98μg/m3) was associated with an increased risk of global cognitive impairment (adjusted odds ratio = 4.56; β= –0.60). High-level PMcoarse exposure (>26.50μg/m3) was associated with poor verbal fluency (β= –0.19). High-level PM10 exposure (>51.20μg/m3) was associated with poor executive function (β= –0.24). Medium-level NO2 exposure (>28.62 ppb) was associated with better verbal fluency (β= 0.12). Co-exposure to high concentrations of PM2.5, PMcoarse or PM10 and high concentration of NO2 were associated with poor verbal fluency (PM2.5 and NO2: β= –0.17; PMcoarse and NO2: β= –0.23; PM10 and NO2: β= –0.21) and poor executive function (PM10 and NO2: β= –0.16). These associations became more evident in women, apolipoprotein ɛ4 non-carriers, and those with education > 12 years. Conclusion: Long-term exposure to PM2.5 (higher than TEPA guidelines), PM10 (lower than TEPA guidelines) or co-exposure to PMx and NO2 were associated with poor global, verbal fluency, and executive function over 4 years.