Individuals who have abnormal findings on Exercise stress testing are more likely to have lower than higher socioeconomic status, and these physiologic characteristics may help account for the correlation between low SES and a higher rate of death, according to a study in the February 15 issue of JAMA.

Previous research has found that lower socioeconomic status (SES) is associated with an increased risk for cardiovascular illness and death. Studies have suggested that individuals with lower SES may have fewer options for safe outdoor exercise, purchase less healthy foods, and have greater exposure to tobacco vendors and tobacco-related public advertisements, characteristics that have the potential to contribute to impaired functional capacity, according to background information in the article.

Mehdi H. Shishehbor, D.O., M.P.H., of The Cleveland Clinic, Cleveland, and colleagues examined whether specific abnormalities on Exercise stress testing, including functional capacity and heart rate recovery, are associated with lower SES and account for a portion of the higher risk of cardiovascular death.

The study, conducted between 1990 and 2002, included 30,043 patients who were referred for stress testing for evaluation of known or suspected coronary artery disease. Patient follow-up to determine the death rate continued through February 2004.

The researchers found that after adjusting for demographics, insurance status, smoking status, and clinical confounders, there was a strong association between a composite SES score based on census block data and functional capacity as well as heart rate recovery. Risk of death increased from 5 percent to 10 percent as SES decreased by quartile. Further analysis determined that functional capacity and heart rate recovery accounted for 47 percent of this association.

People in the lowest SES quartile had nearly twice the rate of death when compared to those in the highest SES quartile. The association between SES and death rate was particularly strong in people who had an impaired functional capacity.

“Our findings may have important public health implications. First, functional capacity and heart rate recovery may be particularly useful for identifying economically disadvantaged patients who are potentially at greatest risk,” the authors write. “Second, use of these physiological characteristics may also prove valuable as a means of monitoring the effectiveness of community-based interventions to reduce disparities in mortality. Third, given the link between functional capacity, heart rate recovery, and mortality, our data lend support to a public policy approach that invests in, for example, recreational facilities.”

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