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Smog Raises Heart Risks in Those With Diabetes, Study Says

Long-term study showed prolonged exposure linked to heart disease, stroke

By Maureen Salamon
HealthDay Reporter

WEDNESDAY, Nov. 25, 2015 (HealthDay News) -- Long periods of exposure to air pollution -- including dust and car exhaust -- heightens heart risks for women with diabetes, a large, new study indicates.

Building on prior research linking shorter exposures to air pollution to higher heart disease in the general population, the scientists found that those with diabetes are especially vulnerable.

"People respond differently to levels of air pollution, and our study was uniquely suited to look at this," said study author Jaime Hart, an assistant professor of medicine at Brigham and Women's Hospital in Boston.

"There's pretty robust literature about the short-term effects of air pollution suggesting those with diabetes are at risk, so it's nice that our results actually went along with [that]," she added.

The study was published Nov. 25 in the Journal of the American Heart Association.

Heart disease is a well-established major complication of diabetes, which affects 29 million people in the United States, and about 65 percent of those with diabetes die from heart disease and stroke, according to the U.S. National Institutes of Health.

Hart and her team analyzed more than 114,000 women (average age 64) who participated in the Nurses' Health Study, which was initiated in 1976. The researchers tallied the incidence of heart disease and strokes in relation to the impact of exposure to three different sizes of so-called "particulate matter" air pollution.

These "particulates" include fine pollutants smaller than a speck of dust and invisible to the human eye, such as those created from car and power plant combustion. Particulates larger than those are created from windblown dust, road dust, and crushed or ground matter. A third level of particulates contains a combination of the first two.

In the research, which encompassed 17 years of follow-up, women with diabetes had a 44 percent increase in cardiovascular disease and 66 percent increase in stroke with extended exposure to the smallest air pollutant particulates. Those heart disease risks were lower but still statistically significant for road dust-type air pollution exposure or exposure to a combination of particulate pollutants, the findings showed.

Hart pointed out that the smaller the particulate matter, the further it can get into an exposed person's lungs, spurring inflammation that can lead to blood vessel blockage. Evidence suggests that the smallest particulates can even cross from the lungs into the bloodstream, she said.

"They don't get cleared out of the system as easily," said Hart, also an assistant professor in the department of environmental health at the Harvard T.H. Chan School of Public Health in Boston. "Air pollution has adverse health effects for everyone, but people in these more sensitive groups may want to get more protection. If they live in areas with large amounts of industrial pollution, they should keep their windows closed."

Dr. John Day, director of heart rhythm services at Intermountain Medical Center Heart Institute in Murray, Utah, said the findings would probably also apply to men with diabetes, despite the fact that men weren't included in the research.

"This study is right in line with a number of other publications showing that air pollution is an important cause of heart disease," said Day. "Patients with diabetes are already at increased risk . . . and air pollution just further amplifies this risk."

Day pointed out that data about day-to-day air pollution levels in most major cities is easily available online and can be used to make decisions about indoor or outdoor activities.

"If particulate matter readings are particularly high, that's a day you probably want to stay inside -- especially for someone with diabetes -- with these types of findings," he said. "Conversely, when the air is good, it's a great opportunity to exercise outside."

Dr. C. Huie Lin, a cardiologist with Houston Methodist DeBakey Heart & Vascular Center in Texas, said he would counsel patients who are employed in fields with higher air pollution exposures to take measures to protect their health.

"It's important as a doctor to treat the whole patient," said Lin. "If they're exposed to particulate matter -- we're also talking about dust and rock dust -- then as a physician, it does compel me to make sure my patients take precautions."

More information

The U.S. Environmental Protection Agency offers more information on air pollution and particulate matter.

SOURCES: Jaime Hart, Sc.D., assistant professor, medicine, Brigham and Women's Hospital and Harvard Medical School, and assistant professor, department of environmental health, Harvard T.F. Chan School of Public Health, Boston; John Day, M.D., director, heart rhythm services, Intermountain Medical Center Heart Institute, Murray, Utah, and president, Heart Rhythm Society, Washington, D.C.; C. Huie Lin, M.D., Ph.D., cardiologist, Houston Methodist DeBakey Heart & Vascular Center, Houston; Nov. 25, 2015, Journal of the American Heart Association

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