Air pollution is a major risk factor for cardiovascular disease, and some people may be more susceptible to its effects than others. Investigators from Brigham and Women's Hospital (BWH) and Harvard T. H. Chan School of Public Health used data from a nationwide study of nurses to look for factors that made people more vulnerable to the effects of long-term air pollution exposure. One factor in particular stood out to the researchers: type 2 diabetes. The team reports its findings in a paper published November 25 in the Journal of the American Heart Association Report.
"We didn't expect diabetes to be the strongest factor in determining susceptibility," said study lead author Jaime E. Hart, Sc.D., an epidemiologist in the Channing Division of Network Medicine at BWH and the Department of Environmental Health at 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 research team explored data from more than 100,000 participants in the Nurses' Health Study (NHS), looking at rates of cardiovascular disease, specifically incidence of coronary heart disease and stroke. They assessed long-term exposure to three different sizes of particulate matter air pollution 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. (For the general population of women in the study, the researchers found that long-term exposure to air pollution led to small, but not statistically significant, increases in risk of cardiovascular events.)
The team found that for each increase of 10 micrograms per cubic meter of air pollution (the equivalent of the difference in air quality between a city like Los Angeles, CA and a city like St. Louis, MO), a woman's risk of cardiovascular disease increased by 44 percent if she had type 2 diabetes. The team found that these effects were greater in women over the age of 70, obese, and/or living in the northeast or south.
The researchers note that exposure data may be less accurate for earlier time points in their study due to fewer air pollution monitoring stations before 1999, and that these results are based on participants' residential addresses, which may not necessarily be where they spent most of their time. In addition, since the NHS is predominantly made up middle-aged to elderly white women, further studies will be needed to determine if these patterns are also seen in men and in racially and socioeconomically diverse populations.
"Continuing to identify subgroups that are most susceptible to the effects of air pollution is critically important for setting pollution standards and regulations so that those who are most vulnerable can be protected," said Hart. "Individuals, especially those who may be at greater risk, can also take precautions to help limit their exposure. And we would always recommend that individuals don't smoke, eat a healthy diet, and get regular exercise to reduce their risk for cardiovascular disease." Senior author Francine Laden, ScD, Professor in the Departments of Environmental Health and Epidemiology at Harvard Chan School, added, "We are currently working to determine if individuals who make healthier lifestyle choices are less susceptible to the adverse impacts of air pollution, and to determine if similar patterns of susceptibility are seen in men."
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Other researchers who contributed to this work include Robin C. Puett, Ph.D.; Kathryn M. Rexrode, M.D., M.P.H.; Christine M. Albert, M.D., M.P.H.; and Francine Laden, Sc.D. This work was supported by the National Institutes of Health (grants R01 ES017017, UM1 CA186107, R01 HL034594, and R01 HL088521) and American Heart Association Science (Development Grant #13SDG14580030).
Brigham and Women's Hospital (BWH) is a 793-bed nonprofit teaching affiliate of Harvard Medical School and a founding member of Partners HealthCare. BWH has more than 4.2 million annual patient visits, nearly 46,000 inpatient stays and employs nearly 16,000 people. The Brigham's medical preeminence dates back to 1832, and today that rich history in clinical care is coupled with its national leadership in patient care, quality improvement and patient safety initiatives, and its dedication to research, innovation, community engagement and educating and training the next generation of health care professionals. Through investigation and discovery conducted at its Brigham Research Institute (BRI), BWH is an international leader in basic, clinical and translational research on human diseases, more than 1,000 physician-investigators and renowned biomedical scientists and faculty supported by nearly $600 million in funding. For the last 25 years, BWH ranked second in research funding from the National Institutes of Health (NIH) among independent hospitals. BWH continually pushes the boundaries of medicine, including building on its legacy in transplantation by performing a partial face transplant in 2009 and the nation's first full face transplant in 2011. BWH is also home to major landmark epidemiologic population studies, including the Nurses' and Physicians' Health Studies and the Women's Health Initiative as well as the TIMI Study Group, one of the premier cardiovascular clinical trials groups. For more information, resources and to follow us on social media, please visit BWH's online newsroom.
Harvard T.H. Chan School of Public Health brings together dedicated experts from many disciplines to educate new generations of global health leaders and produce powerful ideas that improve the lives and health of people everywhere. As a community of leading scientists, educators, and students, we work together to take innovative ideas from the laboratory to people's lives--not only making scientific breakthroughs, but also working to change individual behaviors, public policies, and health care practices. Each year, more than 400 faculty members at Harvard Chan School teach 1,000-plus full-time students from around the world and train thousands more through online and executive education courses. Founded in 1913 as the Harvard-MIT School of Health Officers, the School is recognized as America's oldest professional training program in public health.
Contact: Haley Bridger
Brigham and Women's Hospital
617-525-6383, hbridger@partners.org
Contact: Todd Datz
Harvard T.H. Chan School of Public Health
617-432-8413, tdatz@hsph.harvard.edu