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Air Pollution and Cardiovascular Risk

Exposure differences within cities matter, according to Women’s Health Initiative data.

The Women's Health Initiative Observational Study, a study of postmenopausal women age 50 to 79, gave investigators an opportunity to elucidate the effect of air pollution on the risk for cardiovascular disease (CVD). The current analysis included the 65,893 subjects who were free of CVD at baseline, returned a follow-up questionnaire annually, and could be matched by residence area to a nearby measurement of particulate matter (obtained by the Environmental Protection Agency).

During follow-up (median, 6 years), 1816 subjects had a first cardiovascular event (MI, revascularization, stroke, or death from either coronary heart disease or cerebrovascular disease). Each 10-µg/m³ increase in the level of PM_2.5 (particulate matter <2.5 µm in diameter) was associated with significantly increased risks for cardiovascular events (adjusted hazard ratio, 1.24) and death definitely linked to coronary heart disease (AHR, 2.21). Air pollution also was associated with increased risks for stroke and death from stroke.

Comment: This study substantially strengthens the evidence linking air pollution and CVD (e.g.,Journal Watch Cardiology Jan 7 2005). Prior studies have focused on differences between cities, whereas this study, which found substantial within-city variation, shows a strong association at the level of the individual. The mechanisms by which fine particulate matter may mediate vascular risk are yet to be understood, but these findings suggest that efforts to control air pollution might reduce cardiovascular risk.

— Harlan M. Krumholz, MD, SM

Published in Journal Watch Cardiology January 31, 2007

Citation(s):

Miller KA et al. Long-term exposure to air pollution and incidence of cardiovascular events in women. N Engl J Med 2007 Feb 1; 356:447-58.

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• Medline abstract (Free)

Dockery DW and Stone PH. Cardiovascular risks from fine particulate air pollution. N Engl J Med 2007 Feb 1; 356:511-3.

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• Medline abstract (Free)