How Air Pollution Causes Stroke and Shrinks Brain, Revealed

Researchers have finally uncovered the mysterious link between air pollution and stroke that could serve a wakeup call for urban population world over.

The study conducted by researchers at Harvard T.H. Chan School of Public Health and Beth Israel Deaconess Medical Center between 1995 and 2005 through magnetic resonance imaging (MRI) showed that for every two microgram per cubic meter of air increase in particulate matter measuring 2.5 microns or less (PM _2.5) brain cerebral volume shrunk by 0.32 percent and an risk of deep infarcts, silent precursors to stroke, increased by an alarming 46 percent. The rate of increase in PM _2.5 that researchers used to calculate risk exists in many metropolitan cities across the globe.

"We found that people who live in areas where there are higher levels of air pollution had smaller total cerebral brain volume and were more likely to have evidence of covert brain infarcts," said lead author Elissa H. Wilker.

"The magnitude of association that we observed for brain volume was similar to approximately one year of brain aging," Wilker added.

Infarcts deep in brain have been linked to poor memory and cognition besides hampering functioning of the smallest of the vessels that could lead to stroke without symptoms.

According to WHO nearly seven million people were killed by air pollution in 2012 of which 40 percent of the deaths were caused by stroke.

The study has been published in the journal Stroke.