BRAIN health may be affected even by relatively low levels of air pollution, with Canadian researchers reporting poorer cognitive performance and higher odds of covert vascular brain injury among adults exposed to fine particulate matter and nitrogen dioxide.
Canadian Cohort Explores Environmental Effects on Brain Health
Air pollution is already recognised as a dementia risk factor, but its role in earlier cognitive dysfunction remains uncertain, particularly in countries with comparatively low pollution levels. Investigators therefore examined whether long-term exposure to common pollutants was associated with brain health outcomes in middle-aged adults living across Canada.
Cross-Sectional Analysis of Pollution and Cognitive Outcomes
This cross-sectional analysis used data from the Canadian Alliance for Healthy Hearts and Minds Cohort Study, which recruited adults between 2014 and 2018 across five Canadian provinces. Researchers included 6,878 participants with mean age 57.6±8.8 years, of whom 55.6% were women. Five-year average exposures before enrolment were calculated for fine particulate matter and nitrogen dioxide. Mean fine particulate matter concentration was 6.9 μg/m³ (SD 2.0; range 1.8–11.2), while mean nitrogen dioxide concentration was 12.9 parts per billion (SD 5.9; range 0.9–33.9). Cognitive outcomes included Montréal Cognitive Assessment and Digit Symbol Substitution Test scores, while covert vascular brain injury was measured using MRI.
Higher Pollution Exposure Associated With Poorer Scores
Adjusted analyses showed that each 5 μg/m³ increase in fine particulate matter was associated with 0.44-point lower Montréal Cognitive Assessment scores (95% CI −0.62 to −0.25) and 1.31-point lower Digit Symbol Substitution Test scores (95% CI −2.41 to −0.22). Each 5 parts per billion increase in nitrogen dioxide exposure was associated with 0.12-point lower Montréal Cognitive Assessment scores (95% CI −0.17 to −0.07) and 0.38-point lower Digit Symbol Substitution Test scores (95% CI −0.70 to −0.05). Nitrogen dioxide exposure was additionally associated with increased odds of covert vascular brain injury, with adjusted odds ratio 1.08 (95% CI 1.00–1.17). Cardiovascular risk factors and greenspace did not significantly alter these associations.
Implications for Public Health and Prevention
The findings suggest that long-term exposure to common pollutants may negatively influence brain health even in lower-pollution environments. Researchers highlighted the need for longitudinal studies to determine whether reducing air pollution exposure could help prevent cognitive decline and protect neurological health over time.
Reference
Azab SM. Association of air pollution with brain health: a cross-sectional analysis in adults living in Canada. medRxiv. 2025;2025-10.
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