Association between long-term exposure to ambient PM_2.5 and NO₂ and cognitive function in the CARTaGENE cohort

Ambient air pollution is a recognized risk factor for cardiopulmonary disease, but its effects on cognition remain unclear, particularly at low exposure levels. This cross-sectional study assessed whether long-term exposure to fine particulate matter (PM_2.5) and nitrogen dioxide (NO₂) was associated with cognitive measures in the CARTaGENE cohort.

The analysis included 6659 participants aged 40-69 years from four urban areas in Quebec, Canada. Cognitive function was assessed from computerized tests of processing speed, working memory, and reasoning. Average exposures over the past 11 and 6 years were estimated by linking residential postal codes to PM_2.5 and NO₂ concentrations from satellite-based and land-use regression models, respectively. Associations with standardized cognitive scores were examined using mixed-effect models adjusted for potential confounders. Effect modification by sex, education, and smoking status was explored in subgroup analyses.

Each interquartile range increase in 11-year PM_2.5 exposure was associated with slower processing speed (β = -0.079; 95% CI: -0.121, -0.037). NO₂ exposure was associated with a poorer working memory (β = -0.053; 95% CI: -0.11, 0.004). Both pollutants were associated with better reasoning scores (β for PM_2.5 = 0.059; 95% CI: 0.031, 0.087 and β for NO₂ = 0.108; 95% CI: 0.053, 0.164). Results were similar for the 6-year exposure window. Associations between NO₂ and working memory were modified by the smoking status and education level.

Long-term exposure to low levels of ambient PM_2.5 was associated with slower reaction times and NO₂ to poorer visual working memory.