The Relationship of Socioeconomic Status and Health Status to Outcomes following Heart Attack

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The summary below is from the full report titled "Socioeconomic Status and Mortality after Acute Myocardial Infarction." It is in the 17 January 2006 issue of Annals of Internal Medicine (volume 144, pages 82-93). The authors are D.A. Alter, A. Chong, P.C. Austin, C. Mustard, K. Iron, J.I. Williams, C.D. Morgan, J.V. Tu, J. Irvine, and C.D. Naylor, for the SESAMI Study Group.

What is the problem and what is known about it so far?

Blockages in the blood vessels to the heart can limit blood flow. If low blood flow lasts long enough, a section of heart tissue dies. This condition is known as a myocardial infarction, which is commonly called a "heart attack." Researchers have observed that poorer people do worse after heart attack than wealthier people. One potential explanation for this observation is that poorer patients are more likely than wealthier patients to have risk factors for heart disease, such as smoking, diabetes, and high blood pressure. Some experts speculate that poorer patients have more stress, which might contribute to worse outcomes. Other explanations might be that poor patients do not have good access to health care or have difficulty making positive changes in their lifestyle after they have a heart attack.

Why did the researchers do this particular study?

To examine the relationships between health factors, income, and death within 2 years after a heart attack.

Who was studied?

3407 patients hospitalized for heart attacks between December 1999 and February 2003 in 53 large hospitals in Canada.

How was the study done?

The researchers collected information from patients about income, heart disease risk factors, and health conditions. They also collected information about the patients' health conditions and any deaths from administrative health records. The researchers then compared the rates of death within 2 years after the heart attack for patients with low, medium, and high incomes. Comparisons were made with and without adjustments for differences in health factors. The researchers used Canadian taxation levels to define the income groups.

What did the researchers find?

In the high income group, 7.1% of patients died within 2 years compared with 15.3% of those in the low income group. However, the difference became much smaller and was no longer statistically significant after the researchers adjusted for age, risk factors, and health conditions. This means that the difference was similar to the differences one would expect to see by chance alone rather than a true difference.

What were the limitations of the study?

Information on income and health conditions was gathered from patient self-reports and administrative data.

What are the implications of the study?

Differences in health conditions and risk factors seem to explain why poor people do worse than wealthy people after heart attack. Better management of risk factors and health conditions might improve heart attack outcomes in the poor.