Continued exposure to polluted air could cause indirect physical modifications in the brain that may lead to cognitive impairment and unnoticeable brain injury, according to a study published in the American Heart Association journal Stroke.
Fine particle air pollution, with a diameter of 2.5 millionth of a meter (PM2.5), is regarded as hazardous and usually comes from car exhaust, burning coal or wood, and factory and power station emissions.
The microscopic particles have previously been shown to cause lung damage and the narrowing of blood vessels in the brain. Previous research has related it to heart attacks and strokes.
"Long-term exposure to air pollution showed harmful effects on the brain in this study, even at low levels, particularly with older people and even those who are relatively healthy," stated Elissa H. Wilker, Sc.D., lead author of the study and research associate at the Harvard School of Public Health.
Scientists evaluated 943 adults in the Framingham Offspring Study, who were at least 60 years old, in relatively good physical shape and not diagnosed with stroke and dementia. The test subjects lived in and around Boston county and all over New York and New England, areas where levels of air pollution are relatively low compared to other locations in the world.
The researchers then examined satellite images to evaluate prolonged exposure to air pollution. They utilized magnetic resonance imaging (MRI) to look at the brain structures of the participants, and compared the images with the air pollution levels in the places where the participants lived.
The assessment included white matter volume, which can be a basis of measuring aging and pathology; hippocampal volume, which reveals changes in the region of the brain that manages memory; and total cerebral brain volume, an indicator of age-associated brain atrophy.
This is the first study to examine a link between air pollution, brain volume and the risk of silent strokes in a population of older adults, the researchers said.
The study discovered that an increase of only 2 micrograms per cubic meter of air in PM2.5, a quantity normally witnessed across U.S. cities, was linked to the occurrence of a 0.32 percent smaller total cerebral brain volume and ischemic stroke, comparable to nearly 12 months of brain aging.
These outcomes are consistent with previous research on the relationship between living close to high-traffic roadways, along with long-term exposure to traffic-related air pollution, and poorer cognitive functions and first-time stroke in elder adults.
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