A new study from the Icahn School of Medicine at Mount Sinai quantifies the cardiovascular risk posed by exposure to specific environmental factors, showing, for example, that air pollution heightens the risk of heart disease mortality by 17 percent.
The research, published June 24 in PLOS ONE, is the first to examine the impact of multiple environmental risk factors on cardiovascular mortality and may lead to increased patient screening and preventive measures to improve chances of survival.
According to the Institute for Health Metrics and Evaluation, an independent population health research organization based at the University of Washington School of Medicine, environmental hazards were responsible for an estimated 11.3 million deaths in 2019, and 5.1 million of them were from cardiovascular disease.
“This study advances our understanding of which environmental factors may be most detrimental to cardiovascular health,” says first author Michael Hadley, MD, a Fellow in Cardiology and incoming Assistant Professor of Medicine (Cardiology) at the Icahn School of Medicine at Mount Sinai. “By combining many environmental factors in a single model, we could better control for interactions between risk factors, and identify which environmental risk factors matter most for cardiovascular health.”
The study, known as the Golestan Cohort Study, took place in Iran between 2004 and 2008. Participants were from Golestan Province, a lower-income, multi-ethnic, and mostly rural area where cardiovascular disease is the leading cause of death.
Researchers from Mount Sinai Health System and NYU Grossman School of Medicine led this international, multi-center study. They analyzed data from more than 50,000 participants, all over age 40, who completed a detailed lifestyle questionnaire and a physical exam. Within this group, there were more than 2,700 cardiovascular deaths and nearly 6,000 all-cause deaths during a 10-year follow-up period.
Investigators used environmental data from the National Aeronautics and Space Administration along with geographical information systems technology to create maps of eight environmental risk factors across Golestan: ambient fine particulate matter air pollution; how households cooked, heated, and ventilated their homes; how close they lived to traffic; proximity to hospitals that perform percutaneous coronary intervention; neighborhood socioeconomics; population density; the type of land they live on; and whether their location is bright at night. They assigned exposures to participants based on where they lived on these risk maps, and did a statistical analysis to identify associations between death and environmental risk factors, while controlling for traditional risk factors such as obesity, physical inactivity, diabetes, tobacco use, and hypertension.
They found those exposed to the highest levels of outdoor air pollution were 17 percent more likely to die from heart disease compared to those unexposed, and 20 percent more likely to experience all-cause mortality. Participants exposed to indoor burning of wood, dung, or other biomaterials without ventilation were 36 percent more likely to die from heart disease and 23 percent more likely to experience all-cause mortality. People exposed to indoor kerosene burning without ventilation were 19 percent more likely to die from heart disease and nine percent more likely to die from all-cause mortality. For every six miles participants lived away from a catheterization lab, risk of cardiovascular death went up by 2 percent and all-cause mortality by 1 percent; the researchers estimated that most people in this region lived more than 50 miles away from these clinics. Living within roughly .06 miles of a small roadway and .25 miles from a large highway was associated with a 13 percent increased risk of all-cause mortality. Socioeconomic status, population density, nighttime light, and land were not associated with increased risk of death; most other results showed borderline statistical significance.
The researchers also calculated that the burden of heart disease attributed to indoor and outdoor pollution was equivalent to the burden of cardiovascular disease linked to smoking tobacco.
“Our work demonstrates how publicly available data can be used to create risk maps for individual communities, even in rural, low-income settings. Eventually, we expect health systems to use similar approaches to create environmental risk maps for the communities they serve. The data can empower physicians to estimate environmental risks posted to their patients and offer individualized recommendations to mitigate risk,” Dr. Hadley says.
Senior author Rajesh Vedanthan, MD, MPH, an Associate Professor in the Department of Population Health and the Department of Medicine at NYU Langone Health, adds: “For example, a cardiologist in California might screen their patients for risk of exposure to wildfire smoke. Physicians could then recommend key interventions for at-risk patients such as monitoring local air pollution levels, and staying indoors, wearing a mask, or using indoor air filtration to reduce exposures when pollution levels are elevated. Our findings help broaden the disease-risk profile beyond age and traditional personal risk factors.”
The National Heart, Lung, and Blood Institute, part of the National Institutes of Health, helped fund this study.