Short-Term Exposure to Wildfire Smoke and ${\mathrm{PM}}_{2.5}$ and Cognitive Performance in a Brain-Training Game: A Longitudinal Study of U.S. Adults

Background: There is increasing evidence that long-term exposure to fine particulate matter [PM $\le 2.5\mu m$ in aerodynamic diameter (${\mathrm{PM}}_{2.5}$)] may adversely impact cognitive performance. Wildfire smoke is one of the biggest sources of ${\mathrm{PM}}_{2.5}$ and concentrations are likely to increase under climate change. However, little is known about how short-term exposure impacts cognitive function.

Objectives: We aimed to evaluate the associations between daily and subdaily (hourly) ${\mathrm{PM}}_{2.5}$ and wildfire smoke exposure and cognitive performance in adults.

Methods: Scores from 20 plays of an attention-oriented brain-training game were obtained for 10,228 adults in the United States (U.S.). We estimated daily and hourly ${\mathrm{PM}}_{2.5}$ exposure through a data fusion of observations from multiple monitoring networks. Daily smoke exposure in the western U.S. was obtained from satellite-derived estimates of smoke plume density. We used a longitudinal repeated measures design with linear mixed effects models to test for associations between short-term exposure and attention score. Results were also stratified by age, gender, user behavior, and region.

Results: Daily and subdaily ${\mathrm{PM}}_{2.5}$ were negatively associated with attention score. A ${10\mu g/m}^3$ increase in ${\mathrm{PM}}_{2.5}$ in the 3 h prior to gameplay was associated with a 21.0 [95% confidence interval (CI): 3.3, 38.7]-point decrease in score. ${\mathrm{PM}}_{2.5}$ exposure over 20 plays accounted for an estimated average 3.7% (95% CI: 0.7%, 6.7%) reduction in final score. Associations were more pronounced in the wildfire-impacted western U.S. Medium and heavy smoke density were also negatively associated with score. Heavy smoke density the day prior to gameplay was associated with a 117.0 (95% CI: 1.7, 232.3)-point decrease in score relative to no smoke. Although differences between subgroups were not statistically significant, associations were most pronounced for younger (18-29 y), older ($\ge 70y$), habitual, and male users.

Discussion: Our results indicate that ${\mathrm{PM}}_{2.5}$ and wildfire smoke were associated with reduced attention in adults within hours and days of exposure, but further research is needed to elucidate these relationships. https://doi.org/10.1289/EHP10498.