Although it’s known that air pollution is a major risk factor for cardiovascular disease and that some people can be more susceptible to its effects than others, it hasn’t been clear who, in particular, might be among those who are more susceptible and why.
Research by investigators from HMS and the Harvard T. H. Chan School of Public Health have now brought some clarity. Using data from a nationwide study of nurses to look for factors that made people more vulnerable to the effects of long-term exposure to particulate matter, the researchers found one that stood out: type 2 diabetes.
“We didn’t expect diabetes to be the strongest factor in determining susceptibility,” says study lead author Jaime Hart, an HMS assistant professor of medicine at Brigham and Women’s Hospital and an epidemiologist in the Channing Division of Network Medicine at Brigham and Women’s and the Department of Environmental Health at the Harvard Chan School. “We looked at age, family history of cardiovascular disease, weight, smoking status, and region of the country, but diabetes was the most consistent across diseases and across different size fractions of particulate matter.”
The findings appeared November 25, 2015, in the Journal of the American Heart Association.
The research team explored data from more than 100,000 participants in the Nurses’ Health Study, looking at rates of cardiovascular disease, specifically, the incidence of coronary heart disease and stroke. They assessed long-term exposure to three different sizes of particulate matter from 1989 to 2006.
Among women with diabetes, increased risk was statistically significant for all cardiovascular outcomes measured and across all sizes of particulate matter. By contrast, among women without diabetes, the researchers found that the increased risk of cardiovascular events as a result of long-term exposure to air pollution was statistically insignificant.
The team found that for each increase of 10 micrograms per cubic meter of air pollution, which is the equivalent of the difference in air quality in a city like Los Angeles, California, and a city like St. Louis, Missouri, a woman’s risk of cardiovascular disease increased by 44 percent if she had type 2 diabetes. The team found that these effects were also greater in women who were over the age of 70, obese, living in the U.S. Northeast or South, or had all of these factors.