Long-term exposure to air pollution damages brain: Study

Exposure could lead to smaller brain structure and covert brain infarcts

Long-term exposure to air pollution can cause damage to brain structure and impair cognitive function in middle-aged and older adults, scientists, including one of Indian-origin, have found.

Scientists from Beth Israel Deaconess Medical Center and Boston University School of Medicine in the US studied more than 900 participants of the Framingham Heart Study.

They found that long-term exposure to air pollution could lead to smaller brain structure and covert brain infarcts, a type of "silent" ischemic stroke resulting from a blockage in the blood vessels supplying the brain.

The study evaluated how far participants lived from major roadways and used satellite imagery to assess prolonged exposure to ambient fine particulate matter, particles with a diameter of 2.5 millionth of a metre, referred to as PM2.5.

These particles come from a variety of sources, including power plants, factories, trucks and automobiles and the burning of wood.

They can travel deeply into the lungs and have been associated in other studies with increased numbers of hospital admissions for cardiovascular events such as heart attacks.

"This is one of the first studies to look at the relationship between ambient air pollution and brain structure," said Elissa Wilker, a researcher in the Cardiovascular Epidemiology Research Unit at Beth Israel Deaconess Medical Center.

"Our findings suggest that air pollution is associated with insidious effects on structural brain ageing, even in dementia- and stroke-free individuals," Wilker said.

Study participants were at least 60 years old and were free of dementia and stroke.

The evaluation included total cerebral brain volume, a marker of age-associated brain atrophy; hippocampal volume, which reflect changes in the area of the brain that controls memory; white matter hyperintensity volume, which can be used as a measure of pathology and ageing; and covert brain infarcts.

The study found that an increase of only 2 microgram per cubic meter in PM2.5, a range commonly observed across metropolitan regions in New England and New York, was associated with being more likely to have covert brain infarcts and smaller cerebral brain volume, equivalent to approximately one year of brain ageing.

"This study shows 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," said Sudha Seshadri, a Professor of Neurology at Boston University School of Medicine and Senior Investigator, the Framingham Study.

"They also had a 46% higher risk of silent strokes on MRI," Seshadri said.

The study is published in the journal Stroke.