Heterogeneous associations of air quality improvement with domain‐specific cognitive function in older women

Abstract

AbstractBackgroundAir pollution is associated with increased risk of cognitive decline and dementia. However, whether and how air quality (AQ) improvement is associated with better cognitive performance across multiple domains is unknown.MethodParticipants included 2,114 women (aged 74‐92 at the enrollment) from the US‐based Women’s Health Initiative Memory Study‐Epidemiology of Cognitive Health Outcomes. Cognitive domains evaluated annually included episodic memory (EM; sum of scores by immediate and delayed recalls of East Boston Memory Test and the word list of modified Telephone Interview for Cognitive Status), language (Verbal Fluency‐Animals), working memory (WM, sum of scores from forward and backward Digit Span Tests), and attention/executive function (AEF, log‐transformed ratio of the time spent in Part A over Part B for Oral Trails Making Test), all standardized using corresponding baseline measure. Annual PM2.5 (fine particulate matter) and NO2 were estimated using regionalized universal kriging models and aggregated to 3‐year average at 10 years (remote) and immediately (recent) before enrollment. AQ improvement was defined as reduction from remote to recent exposures. We examined associations between AQ improvement and domain‐specific cognitive trajectories using linear mixed effect models, adjusting for sociodemographic, lifestyle, clinical covariates, and time‐varying propensity scores to account for selective attrition.ResultsAQ improved significantly over 10 years for both PM2.5 (13.3±2.7µg/m3 to 10.6±2.0µg/m3) and NO2 (15.7±7.1ppb to 10.4±4.9ppb). Over a median of 6.2 (inter‐quartile‐range [IQR]=5.1) years of follow‐up, cognitive performance declined significantly in all domains. Women residing in locations with greater PM2.5 improvement (per IQR=1.77µg/m3) had better performance in EM (βPM2.5=0.069, p=0.002), WM (βPM2.5=0.050, p=0.01), and AEF (βPM2.5=0.044, p=0.01), but not in language (βPM2.5=0.013, p=0.57). Similar findings with stronger associations were observed with improved NO2 (βNO2=0.065∼0.073 per IQR=3.89ppb for EM, WM and AEF, all p≤0.002). Slower declines in cognitive trajectories across EM, Language and AEF were found with improved AQ, but only the association between improved NO2 and slower EM decline was statistically significant (βNO2=0.010/year, p<0.001).ConclusionsImproved AQ of PM2.5 and NO2 was associated with better performance of EM, WM and AEF, but not language. In addition, improved NO2 was associated with slower decline of EM over time in older women.