Connection between air pollution and cardiovascular disease

Researchers at the University of Washington will direct the largest study of its kind to explore the connection between air pollution and the No. 1 cause of death in the United States: cardiovascular disease.

"We're going to be looking at questions vital to our understanding of the health effects of air pollution and cardiovascular disease," said Dr. Joel Kaufman, principal investigator on the project and associate professor in the Department of Environmental and Occupational Health Sciences in the UW School of Public Health and Community Medicine.

"There's a lot yet to be understood about what explains cardiovascular disease besides the known factors such as high cholesterol, hypertension and diabetes. There are still many unexplained variations in who gets heart disease, and when they get it. Some of the explanation is likely to come from studying environmental factors," Kaufman said. "We hope this study will really define the contribution of particulate air pollution to cardiovascular disease."

The $30 million grant will be funded over 10 years by the United States Environmental Protection Agency (please see companion news release).

"We have a national strategy to dramatically improve America's air quality," said EPA Administrator Mike Leavitt. "An important component of this strategy is to improve our understanding of the health risks from long-term exposure to particulate pollution, particularly as it relates to coronary heart disease, the leading cause of death in our country."

This is the first major prospective cohort study designed to look at the chronic impacts of long-term exposure to air pollution on cardiovascular health. The study will look at both subclinical measures of atherosclerosis -- by ultrasound of the carotid arteries and CT scan of the coronary arteries -- as well as clinical cardiovascular events such as heart attacks and strokes. Exposure to air pollution will be calculated using state-of-the-art measurements from monitors in several communities and questionnaires from subjects.

Participants will be followed for 10 years. About 8,700 people will be recruited in nine communities in California, Illinois, New York, North Carolina, Maryland and Minnesota. Many of the people expected to participate are already enrolled in other studies of cardiovascular health.

Prior studies that included pollution and cardiovascular disease were originally designed to study other factors. They were either not originally designed to study heart disease or not originally designed to study air pollution, Kaufman said. For example, previous studies have focused on studying the effect of air pollution on the respiratory system or on cancer, with cardiovascular effects studies as a secondary element.

But despite their shortcomings, these prior studies show enough of an effect that clearly warrants nationwide action to limit exposures and conduct further investigation, Kaufman said. The results from the new study should also form a very firm foundation for the most appropriate public health actions, including government regulation of air quality.

"You could look at those previous studies and say it's as simple as 'Shouldn't we just have less pollution?' In a sense it is really that simple -- and the current scientific evidence is clear enough to take action for cleaner air. But some people have raised questions about whether the existing studies really form a strong enough scientific basis to be regulating against pollution. This study is designed to answer those questions," Kaufman said.

The study will be based at the UW in Seattle, and will include faculty from the UW departments of Environmental and Occupational Health Sciences, Biostatistics and Epidemiology in the School of Public Health and Community Medicine, as well as the departments of Medicine, Statistics, Geography and Civil and Environmental Engineering.

Collaborating institutions include the University of California, Los Angeles; Columbia University; Northwestern University; University of Minnesota; Johns Hopkins; Wake Forest; University of Vermont; Tufts-New England Medical Center; and the University of Michigan.

Kaufman, an attending physician in internal medicine, is also director of the UW Occupational and Environmental Medicine Program, associate professor of medicine, and an adjunct associate professor of epidemiology. Kaufman is a member investigator of the School of Public Health's existing EPA Northwest Research Center for Particulate Air Pollution and Health. The new study is built on the foundation of the National Institutes of Health's Multi-Ethnic Study of Atherosclerosis (MESA) study, whose coordinating center is directed by Dr. Richard Kronmal of the school's Department of Biostatistics.

The 6,600 participants currently involved in the MESA study will be approached for recruitment into this new study. Some new subjects will also be recruited in specific communities in California and New York. The recruiting method has not been announced.

The study will be able to take into account dietary information, family health history, smoking history, exposure to second-hand tobacco, and other factors known or suspected related to cardiovascular disease.

One of the weaknesses of most previous studies was that their researchers could only assume everyone in a particular city has the same exposure to pollution, Kaufman said. In fact, that's not true. Exposures vary within a metropolitan area. Pollution varies in a community depending on such variables as wind direction, geographic features and proximity to highways or other sources of pollution. The study will use existing air quality monitors in the cities under study, but also use new monitoring networks to characterize air pollution exposures down to the level of the neighborhood. The researchers will use a limited number of home and even personal monitors to estimate participants' pollution exposures. For example, the researchers will test exposures by putting monitors outside the homes of about 3,600 participants at certain times.

The new study will make unprecedented efforts to pinpoint the air pollution exposures of people involved in the study. The researchers will look at how much time participants spend outside in various activities throughout the day, and how that affects their exposures.

By employing state-of-the-art scientific methods, this study will result in a tremendous amount of new information on the effects of air pollution, and contribute to efforts to prevent heart disease in the future, the researchers hope.