Air pollution, even at moderate levels, may raise your risk of having a stroke, past studies have shown. Now, a new study suggests air pollution may have other damaging effects, at least for middle-aged and older adults. Long-term exposure to air pollution appears to damage brain structures and impair mental function, the researchers found, in older people without dementia or stroke.

“For this study, we looked at exposure over only one year in a population of people over the age of 60,” Dr. Elissa Wilker of the Cardiovascular Epidemiology Research Unit at Beth Israel Deaconess Medical Center told Medical Daily. While she dares not speculate whether air pollution similarly harms younger people, she and her colleagues are “trying to understand what this means over time,” since “this probably is about longer-term exposures” to air pollution.

The research tracked more than 900 Framingham Heart Study participants — all were at least 60 years old and free of dementia and stroke. The researchers evaluated how far participants lived from major roadways and then used satellite imagery to assess prolonged exposure to ambient fine particulate matter or PM2.5 — particles with a diameter of 2.5 millionth of a meter. Then the researchers examined each participant’s total cerebral brain volume, which is linked to age-associated brain atrophy.

Additionally, they looked at participants’ hippocampus, the area of the brain that controls memory, and the volume of their white matter hyperintensity, which scientists use to measure brain pathology. Finally, they scanned for covert brain infarcts, lesions frequently detected on MRIs that have resulted from a blockage in the blood vessels supplying the brain. Commonly seen as the marks of “silent” stroke, these infarcts are associated with the onset of dementia.

Silent Stroke

The study found that the range of PM2.5 commonly observed across metropolitan regions in New England and New York was linked to participants having smaller cerebral brain volume — equivalent to that of someone one year older — and also linked to the likelihood of participants having brain infarcts.

In fact, those living in these more polluted areas had a 46 percent higher risk of silent strokes.

A variety of sources produce PM2.5. Power plants, factories, trucks and automobiles, and the burning of wood all generate this fine level of particulate matter, which can travel deeply into the lungs. In other studies, PM2.5 has been linked to an increased number of hospital admissions for heart attacks and strokes.

“These findings suggest that relatively low urban background levels of particulate air pollution may contribute to the acceleration of atrophic changes and small-vessel disease in older adults,” the authors wrote in the conclusion of the study.

Asked if people should run from their cities, Wilker laughed. “No,” she said, “instead I always say the most important thing is to try to live a healthy life style.” Keep doing your best!

Source: Wilker E, Preis SR, Beiser AS, et al. Long-Term Exposure to Fine Particulate Matter, Residential Proximity to Major Roads and Measures of Brain Structure. Stroke. 2015.