Living Close to Busy Roads Increases Coronary Calcification

Lisa Nainggolan
July 16, 2007 (Essen, Germany) – A new German study has shown, for the first time, that living near very busy roads is associated with coronary atherosclerosis [1]. Dr Barbara Hoffman (University of Duisberg-Essen, Germany) and colleagues report their findings online July 16, 2007 in Circulation.
"What we found is that living close to heavy traffic is associated with higher calcification in the coronary arteries," Hoffman told heartwire.
"What has been studied previously is particulate matter and proximity to roads in relation to cardiovascular events, but with that, you never know whether it's a short-term effect or not. We are showing it not only triggers short-term effects but influences underlying pathology."
Fine particulate matter associated with CAC in those at home
The study of 4494 adults, age 45 to 74 years, is part of the Heinz Nixdorf Recall Study that is being conducted in three large, adjacent cities in the industrialized Ruhr area of Germany. Home address was used to estimate each person's exposure to urban air pollution. Participants were interviewed about risk factors such as diabetes and smoking, underwent extensive clinical examinations, and had their coronary artery calcification (CAC) measured by electron-beam computed tomography (EBCT).
Hoffman told heartwire that the participants were informed of their cardiology workup at baseline, but they were not told their CAC scores, as the idea was to look at how predictive these are for future events. "If we had told them their CAC scores, that could influence the future events," she noted, adding that Germany does not measure CAC scores routinely.
The researchers found that the closer the participant lived to heavy traffic, the higher the CAC. "People who live near a German freeway or federal highway, which can be traveled by 10 000 to 130 000 cars daily, have more atherosclerosis the closer they live to the road," Hoffmann says. "If you live at a distance of, for example, 100 meters from the freeway, then on average you have 7% more calcification in your coronary arteries than a person with the same cardiovascular risk profile who lives 200 meters away."
The fact that they showed a positive exposure-response relationship for increasing traffic exposure that persisted even after multivariable adjustment "strengthens our findings," the researchers say. Adjusted ORs for a CAC score above the age- and gender-specific 75th percentile for the total sample (n=4494)
Five-year follow-up in 2008
Hoffman and colleagues say their results concur with those from a recent study conducted in Los Angeles, which showed an increase in carotid intima-media thickness of 5.9% for an exposure contrast of 10 µg/m3 PM2.5.
"We examined small-scale differences in traffic exposure and used a different outcome, making quantitative comparisons of associations difficult," they note. "Both studies, however, show an association between long-term air pollution and well-established quantitative measures of atherosclerosis."
Nevertheless, the findings require corroboration in prospective studies, they state.
Hoffman told heartwire that her team is looking at other surrogate markers within the same German population, such as carotid intima-media thickness and ankle-brachial index. Also, next year they will have five-year follow-up data on the cohort, and they will be looking at progression of coronary atherosclerosis.
"Until then," she says, "politicians, regulators, and physicians need to be aware that living close to heavy traffic may pose an increased risk of harm to the heart.
"Potential harm due to proximity to heavy traffic should be considered when planning new buildings and roads. And clinicians and cardiologists need to be aware that a patient's proximity to heavy traffic may be a factor that should be considered when assessing patients with coronary artery disease."
Hoffman B, Moebus S, Mohlenkamp S, et al. Residential exposure to traffic is associated with coronary atherosclerosis. Circulation 2007; DOI: 10.1161/circulationaha.107.693622. Available at: http://circ.ahajournals.org.