Ambient Air Pollution and Long-Term Trajectories of Episodic Memory Decline among Older Women in the WHIMS-ECHO Cohort

BACKGROUND: Episodic memory decline varies by age and underlying neuropathology. Whether ambient air pollution contributes to the heterogeneity of episodic memory decline in older populations remains unclear. OBJECTIVES: We estimated associations between air pollution exposures and episodic memory decline according to pollutant, exposure time window, age, and latent class subgroups defined by episodic memory trajectories. METHODS: Participants were from the Women’s Health Initiative Memory Study–Epidemiology of Cognitive Health Outcomes. Older women ([Formula: see text]; 74–92 years of age) completed annual (2008–2018) episodic memory assessments using the telephone-based California Verbal Learning Test (CVLT). We estimated 3-y average fine particulate matter [PM with an aerodynamic diameter of [Formula: see text] ([Formula: see text])] and nitrogen dioxide ([Formula: see text]) exposures at baseline and 10 y earlier (recent and remote exposures, respectively), using regionalized national universal kriging. Separate latent class mixed models were used to estimate associations between interquartile range increases in exposures and CVLT trajectories in women [Formula: see text] and [Formula: see text] , adjusting for covariates. RESULTS: Two latent classes were identified for women [Formula: see text] ([Formula: see text]), “slow-decliners” {[Formula: see text] [95% confidence interval (CI): [Formula: see text] , [Formula: see text]] and “fast-decliners” [[Formula: see text] (95% CI: [Formula: see text] , [Formula: see text])]}. In the slow-decliner class, but not the fast-decliner class, [Formula: see text] exposures were associated with a greater decline in CVLT scores over time, with a stronger association for recent vs. remote exposures [[Formula: see text] (95% CI: [Formula: see text] , [Formula: see text]) per [Formula: see text] and [Formula: see text] (95% CI: [Formula: see text] , 0.01) per [Formula: see text] , respectively]. Among women [Formula: see text] ([Formula: see text]), the largest latent class comprised “steady-decliners” [[Formula: see text] (95% CI: [Formula: see text] , [Formula: see text])], whereas the second class, “cognitively resilient”, had no decline in CVLT on average. [Formula: see text] was not associated with episodic memory decline in either class. A [Formula: see text] increase in recent [Formula: see text] was associated with nonsignificant acceleration of episodic memory decline in the [Formula: see text]-y-old fast-decliner class [[Formula: see text] (95% CI: [Formula: see text] , 0.04)], and in the [Formula: see text] cognitively resilient class [[Formula: see text] (95% CI: [Formula: see text] , 0.03)] and steady-decliner class [[Formula: see text] (95% CI: [Formula: see text] , 0.05)]. Associations with recent [Formula: see text] exposure in women [Formula: see text] were stronger and statistically significant when 267 women with incident probable dementia were excluded [e.g., [Formula: see text] (95% CI: [Formula: see text] , [Formula: see text]) for the cognitively resilient class]. In contrast with changes in CVLT over time, there were no associations between exposures and CVLT scores during follow-up in any subgroup. DISCUSSION: In a community-dwelling U.S. population of older women, associations between late-life exposure to ambient air pollution and episodic memory decline varied by age-related cognitive trajectories, exposure time windows, and pollutants. https://doi.org/10.1289/EHP7668