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People with lower incomes, lower education levels have higher death rates

June 18, 2008

ROCHESTER, Minn. -- Researchers have long suspected that socioeconomic factors like education level and income also might affect survival rates following heart attack. In the June issue of Mayo Clinic Proceedings, Mayo Clinic researchers present new data suggesting that people with lower incomes and education levels are more likely to die after heart attack than more affluent, educated people. Over the past several decades, medical research has helped identify a list of factors that increase a person's risk for myocardial infarction, the disruption of blood flow to the heart commonly known as heart attack. These factors include behaviors such as smoking or inactivity, and a variety of physical characteristics, including high blood pressure, high blood cholesterol and obesity. Today, better awareness of heart attack signs and symptoms and improved treatments help many survive that first heart attack.

Mayo authors examined medical records from 705 patients residing in Olmsted County, Minn. -- the location of Mayo Clinic -- who were treated for heart attack between Nov. 1, 2002 and May 31, 2006. Researchers recorded the years of schooling completed (self-reported by the patients via a questionnaire) and neighborhood income (obtained by linking the participant address to the 2000 U.S. Census Bureau data) for each participant. Participants were divided into three income groups and three education groups. Researchers analyzed survival data across these different groups.

Among the 155 deaths recorded during the study period, one-year survival estimates across income groups were lowest for people with the lowest income. Seventy-five percent were survivors among people earning $28,732 to $44,665; 83 percent survived among people earning $49,435 to $53,561; and 86 percent survived among people earning $56,992 to $74,034. Similarly, the survival rates were lowest for participants with less education. Sixty-seven percent were survivors among those who had fewer than 12 years of education; 81 percent survived among people with 12 years of education; and 85 percent survived among people with greater than 12 years of education.

The authors say that while many previous studies have sought to link socioeconomic status and poor outcomes following heart attack, this study design has yielded some unique results.

"Interestingly, despite the higher-than-average socioeconomic status of this population, the associations of individual education and neighborhood income with death after heart attack were stronger than those reported in many previous studies," notes Mayo Clinic cardiovascular researcher Yariv Gerber, Ph.D., the study's lead author. "We think our approach of evaluating two different and complementary indicators of socioeconomic status allowed us to capture a wider spectrum of this complex theory."

Mayo researchers believe that the association observed for education could be related to education's positive effect on factors that include job opportunities, income, housing, access to nutritious foods and health insurance.

"Higher levels of education also could directly affect health through greater knowledge acquired during schooling and greater empowerment and self-efficacy," writes Dr. Gerber. "As recently reported, education is strongly associated with health literacy, which in turn affects one's ability to obtain, process, and understand basic health information and services needed to make appropriate health decisions."

Mayo researchers also point out that more specific mechanisms linking low socioeconomic status to survival following heart attack could also be related to the greater difficulty that poorer individuals with lower education levels have in attending cardiac rehabilitation programs and adhering to medications and lifestyle recommendations.

Mayo Clinic