Objective: Prior evidence linking fine particulate matter (PM2.5) and cognitive decline is mixed, possibly due to incomplete assessment of follow-up exposure and PM2.5 metal components. We examined associations of baseline and cumulative follow-up PM2.5 mass and metal components with cognitive decline in the Adult Changes in Thought (ACT) cohort.

Methods: This analysis included 5,673 adults aged ≥65 years in the Greater Seattle area, with a median of 5 cognitive assessment over 8 years of follow-up. Spatiotemporal estimates of PM2.5 mass and metal components were linked to residential histories. Linear mixed-effects models with inverse probability of censoring weighting (IPCW) included either baseline exposure × time or cumulative follow-up exposure × time to model rate of change in the outcome. Models were adjusted for baseline age, gender, race/ethnicity, marital status, education, enrollment cohort, neighborhood SES, baseline smoking, natural splines for calendar year, and time interactions for all covariates.

Results: Preliminary results showed PM2.5 mass had largely null associations with cognitive decline, although there was evidence of a small decrease in rate of decline for executive function in the pre-baseline 2-year exposure window (β=0.002, 95% CI: 0.000, 0.004). In contrast, several metal components were associated with domain-specific decline. Sulfur was associated with accelerated decline in executive function (β = −0.033, 95% CI: −0.064 to −0.001) and language (β = −0.041, 95% CI: −0.075 to −0.008). Vanadium was associated with faster decline in visuospatial function (β = −3.652, 95% CI: −6.688 to −0.616). We also observed faster memory decline associated with lead, and accelerated visuospatial decline associated with zinc, silicon, sulfur, and bromine. Copper, in contrast, was associated with a slower rate of memory decline.

Conclusion: Specific PM2.5 metal components, rather than total PM2.5 mass, were associated with accelerated domain-specific cognitive decline. These findings highlight the importance of considering pollutant composition when evaluating the neurodegenerative risk of air pollution.