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The study, published online May 13 in the Journal of Epidemiology and Community Health, involved more than 1,100 adults who were admitted to a Boston-area hospital after suffering a stroke between 1999 and 2004. Half of the participants lived within three-fifths of a mile of a major road. The rest lived up to six miles away.
Each patient underwent two tests to measure how well their kidneys were working. First, a blood test assessed their level of creatinine, a byproduct of muscle metabolism. Their glomerular filtration rate, which shows how well creatinine is filtered out of the body by the kidneys, also was analyzed. A low filtration rate indicates worse kidney function.
Patients who lived closest to a busy road had the lowest glomerular filtration rate, after their age, sex, race, smoking status, and previous treatment for heart disease or other underlying conditions were taken into account, according to a journal news release.
Although the study tied living near heavy traffic to possible harm to kidney function, it did not establish a cause-and-effect relationship.
"If causal, these results imply that exposures associated with living near a major roadway contribute to reduced renal function, an important risk factor for cardiovascular events," wrote Dr. Murray Mittleman, of the cardiovascular epidemiology research unit at Beth Israel Deaconess Medical Center in Boston, and colleagues.
Pollution caused by traffic can lead to the accumulation of arterial plaque and changes to peripheral arteries, the researchers said. The kidneys are very susceptible to the build-up of arterial plaque, they added. Impaired kidney function is a risk factor for cardiovascular disease. Therefore, the researchers suggested, living near a roadway with heavy traffic could contribute to negative effects of air pollution on heart health.
The authors estimated that living very close to a major road was associated with a 4 percent higher rate of cardiovascular death and a 1 percent greater risk of death from any cause compared to the risk of people living at least a few miles away.
"There is growing evidence that living near major roadways contributes to the incidence of vascular disease, and adverse prognosis among patients with prevalent cardiovascular disease," the researchers wrote.
-- Mary Elizabeth Dallas
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