Something is in the air
Pollution tied to Alzheimer's in brain tissue, study finds
People who inhale higher concentrations of tiny airborne particulates, like from diesel exhaust, are more likely to have signs of Alzheimer's disease in their brains, according to a new study, the latest in a growing body of research that shows a link between air pollution and cognitive decline.
For the study, published recently in the journal Neurology, researchers examined the association between concentrations of ambient air pollution and signs of Alzheimer's disease in the brain. They found that people who were exposed to higher concentrations of fine particulate matter air pollution, also known as PM2.5, at least a year before their death were more likely to have higher levels of plaques — abnormal clusters of protein fragments built up between nerve cells, which is a sign of Alzheimer's in brain tissue. The research also found a strong association between the pollution and signs of the disease for people who were not already genetically predisposed to Alzheimer's.
“This suggests that environmental factors like air pollution could be a contributing factor to Alzheimer's disease, especially in patients in which the disease cannot be explained by genetics,” said Anke Huels, the lead author of the study and an assistant professor at Emory University's School of Public Health. While the study does not prove that air pollution causes Alzheimer's disease, it found an association between exposure to specific kinds of pollution and signs of the disease.
Researchers examined tissue from 224 donors in Atlanta's metropolitan area who, before their deaths, donated their brains to research.
“Donors who lived in areas with particularly high levels of traffic-related air pollution showed more plaques related to Alzheimer's disease at death than donors who lived in areas with lower air pollution concentrations,” Huels said.
What that told researchers, she added, is that being exposed to high levels of the pollution increases your risk for Alzheimer's disease.
More than half of the donors had what's known as the APOE gene, the strongest genetic risk factor for Alzheimer's disease. But for the donors who were not already genetically predisposed, researchers found a stronger association between traffic-related air pollution and signs of Alzheimer's disease.
Experts have long been known that concentrations of PM2.5 can trigger short-term respiratory problems. That's because the particulates are so small — measuring 2.5 microns and smaller in diameter — that they enter the bloodstream after being inhaled. Breathing in smoke can also irritate your sinuses, throat and eyes, according to the Centers for Disease Control and Prevention. In severe cases, exposure is linked to heart attacks, stroke, lung cancer and damage to cognitive functions.
Gaurab Basu, the director of education and policy at Harvard's centre for climate, health and the environment, said the study spotlights the dangers of ambient air pollution.
“We often think about air pollution in the lungs, but it's critical that we put the brain at the forefront of the conversation of the ways that air pollution impacts our health,” Basu said.