New clue may explain link between traffic pollution and heart risks


New clue may explain link between traffic pollution and heart risks

For the first time, a study suggests that being exposed to high levels of traffic pollution is linked to changes in the mass and size of the right chamber of the heart. The researchers believe this may contribute to the known connection between air pollution exposure and heart disease.

Lead author Dr. Peter Leary, of the University of Washington Medical Center in Seattle, and colleagues report their findings in the American Journal of Respiratory and Critical Care Medicine.

Dr. Leary, who cites right ventricular failure among his research interests, says while previous studies have already established links between traffic pollution and changes to the left ventricle, heart failure and death from cardiovascular diseases, connections between air pollution and the right ventricle have not been so well studied.

But right heart failure is known to be a cause of common and rare heart and lung diseases, as well as deaths from them, he and his colleagues note in their study report:

"Using exposure to nitrogen dioxide as a surrogate for exposure to traffic-related air pollution, we were able to demonstrate for the first time that higher levels of exposure were associated with greater right ventricular mass and larger right ventricular end-diastolic volume. Greater right ventricular mass is also associated with increased risk for heart failure and cardiovascular death."

For their study, the researchers examined data on over 3,800 participants taking part in the Multi-Ethnic Study of Atherosclerosis.

The participants, who were free of clinical cardiovascular disease, all underwent heart MRI scans.

The researchers then compared the results of the MRI scans with estimates of the participants' exposure to outdoor oxides of nitrogen in the 12 months leading up to the scans.

Oxides of nitrogen, including nitrogen dioxide or NO2, are a family of highly reactive gases that form when fuel is burned at high temperatures and are emitted mainly by motor vehicles and stationary sources, such as electric utilities and industrial boilers.

More exposure to oxides of nitrogen tied to increase in right ventricle mass, volume

The researchers found increased exposure to NO2 was linked with a 5% increase (about 1.0 g) in right ventricular mass and a 3% (4.1 mL) increase in right ventricular end-diastolic volume (the volume of blood in the chamber at the end of filling).

They also found similar relationships between these right ventricle changes and estimates of exposure to overall levels of oxides of nitrogen.

These links remained even after they took into account other things that influence the link, such as differences in the participants' cardiovascular risk factors, the mass and volume of the right side of their hearts, inflammation markers, lung disease and their socioeconomic situation.

The authors are careful to point out certain potential weaknesses in their study. For example, using estimates of air pollution is not always reliable, and it is also possible that it is not air pollution itself but something related to it that could be confounding the analysis and creating the link.

So they conclude while the study does not prove that traffic-related air pollution caused the changes they observed, it strongly points in that direction.

Dr. Leary says their findings add to a growing body of evidence supporting a connection between traffic-related air pollution and cardiovascular disease, and adds:

The many adverse effects of air pollution on human health support continued efforts to reduce this burden."

In April 2013, Medical-Diag.com reported a study by another team of researchers in the US that found over time, increased exposure to air pollution is linked to faster atherosclerosis or hardening of the arteries, a leading cause of heart attacks and strokes. In that study, the team used fine particulate matter, PM2.5, as a measure of air pollution.

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Section Issues On Medicine: Cardiology