Air pollution linked to poorer memory, thinking skills — Study

New research has suggested that air pollution may be having subtle effects on the brain as well as the lungs, with links to reduced memory and thinking ability from everyday exposure.

A study from McMaster University, published in the journal Stroke, found that people living in areas with higher levels of air pollution performed worse on tests measuring memory, comprehension and mental processing speed.

The effects were observed even in regions where pollution levels are considered relatively low by international standards.

Researchers also observed that traffic-related pollution was associated with subtle structural changes in the brain on MRI scans, with a stronger signal seen among women.

The associations remained even after adjusting for major cardiovascular risk factors, including high blood pressure, diabetes and obesity, raising the possibility that air pollution may have a more direct effect on brain health.

The study analysed nearly 7,000 middle-aged adults across five Canadian provinces, drawing on one of the largest investigations of its kind in a country known for comparatively clean air. It focused on fine particulate matter (PM2.5) and nitrogen dioxide, pollutants largely produced by vehicle exhaust, industry and wildfire smoke.

Although previous research has tended to focus on heavily polluted regions, the findings suggest that even low-level, long-term exposure may be associated with measurable differences in cognitive performance.

Lead author Sandi Azab, assistant professor in McMaster University’s Department of Medicine, explained that while Canada’s air is often described as clean, even low levels of air pollution are linked to worse brain health in the study.

“These are changes that can occur quietly, years before any noticeable symptoms appear,” Azab said.

The research team stressed that dementia develops gradually over decades, making it important to identify early, potentially preventable risk factors that may shape brain health later in life.

While the study does not establish that air pollution causes dementia, it adds to a growing body of evidence suggesting that environmental factors may contribute to age-related cognitive decline.

Researchers noted that longer-term studies are needed to determine how sustained exposure affects the brain over time and whether improvements in air quality could help protect cognitive health.