HEALTH NEWS

Study Title:

Air Pollution Increases the Rate of Atherosclerosis

Study Abstract

Background
Cross-sectional studies suggest an association between exposure to ambient air pollution and atherosclerosis. We investigated the association between outdoor air quality and progression of subclinical atherosclerosis (common carotid artery intima-media thickness, CIMT).

Methodology/Principal Findings
We examined data from five double-blind randomized trials that assessed effects of various treatments on the change in CIMT. The trials were conducted in the Los Angeles area. Spatial models and land-use data were used to estimate the home outdoor mean concentration of particulate matter up to 2.5 micrometer in diameter (PM2.5), and to classify residence by proximity to traffic-related pollution (within 100 m of highways). PM2.5 and traffic proximity were positively associated with CIMT progression. Adjusted coefficients were larger than crude associations, not sensitive to modelling specifications, and statistically significant for highway proximity while of borderline significance for PM2.5 (P = 0.08). Annual CIMT progression among those living within 100 m of a highway was accelerated (5.5 micrometers/yr [95%CI: 0.13–10.79; p = 0.04]) or more than twice the population mean progression. For PM2.5, coefficients were positive as well, reaching statistical significance in the socially disadvantaged; in subjects reporting lipid lowering treatment at baseline; among participants receiving on-trial treatments; and among the pool of four out of the five trials.

Conclusion
Consistent with cross-sectional findings and animal studies, this is the first study to report an association between exposure to air pollution and the progression of atherosclerosis – indicated with CIMT change – in humans. Ostensibly, our results suggest that air pollution may contribute to the acceleration of cardiovascular disease development – the main causes of morbidity and mortality in many countries. However, the heterogeneity of the volunteering populations across the five trials, the limited sample size within trials and other relevant subgroups, and the fact that some key findings reached statistical significance in subgroups rather than the sample precludes generalizations to the general population.

From press release:

Swiss, California and Spanish researchers have found that particulates from auto exhaust can lead to the thickening of artery walls, possibly increasing chances of a heart attack and stroke.

In a study reported this week in the journal PLoS ONE, the researchers used ultrasound to measure the carotid artery wall thickness of 1,483 people who lived near freeways in the Los Angeles area. The researchers took these measurements every six months for approximately three years, and correlated them with estimates of outdoor particulate levels at the study participants' homes.

They found that the artery wall thickness among those living within 100 meters (328 feet) of a highway increased by 5.5 micrometers – one-twentieth the thickness of a human hair – per year, or more than twice the average progression observed in study participants.

"For the first time, we have shown that air pollution contributes to the early formation of heart disease, known as atherosclerosis, which is connected to nearly half the deaths in Western societies and to a growing proportion of deaths in the rapidly industrializing nations of Asia and Latin America," said study co-author Michael Jerrett, UC Berkeley associate professor of environmental health sciences. "The implications are that by controlling air pollution from traffic, we may see much larger benefits to public health than we thought previously."

"This study fills an important gap between studies linking mortality to air pollution and those that have reported short-term changes in blood pressure," he added.

Study Information

1.Nino Künzli, Michael Jerrett, Raquel Garcia-Esteban, Xavier Basagaña, Bernardo Beckermann, Frank Gilliland, Merce Medina, John Peters, Howard N. Hodis, Wendy J. Mack.
Ambient Air Pollution and the Progression of Atherosclerosis in Adults
PLoS One
2010 February
Division of Environmental Health Sciences, School of Public Health, University of California, Berkeley, California, United States of America.