A new study led by scientists from Beth Israel Deaconess Medical Centre and Boston University School of Medicine suggests that long-term exposure can cause damage to brain structures and impair cognitive function in middle-aged and older adults.

Researchers studied over 900 participants of the Framingham Heart Study and found evidence of smaller brain structure and of covert brain infarcts, a type of "silent" ischemicstroke resulting from a blockage in the blood vessels supplying the brain.

Elissa Wilker, ScD, a researcher at Beth Israel Deaconess Medical Centre said that the study was one of the first to look at the relationship between ambient air pollution and brain structure, and the findings suggest that air pollution was associated with insidious effects on structural brain aging, even in dementia- and stroke-free individuals.

Professor Sudha Seshadri, MD added that it showed that for a 2 microgram per cubic meter of air increase in PM2.5, a range commonly observed across major US cities, on average participants who lived in more polluted areas had the brain volume of someone a year older than participants who lived in less polluted areas. They also had a 46 percent higher risk of silent strokes on MRI. "This is concerning since we know that silent strokes increase the risk of overt strokes and of developing dementia, walking problems and depression. We now plan to look at more the impact of air pollution over a longer period, its effect on more sensitive MRI measures, on brain shrinkage over time, and other risks including of stroke and dementia."