A new study indicates that competing in the world with little education and low job status can contribute to heart disease survival, but living alone doesn't appear to matter.
Both scenarios social isolation and low socioeconomic status have been discussed for years in the cardiology community as potential contributors to heart disease, and studies to tease out their impact have been contradictory.
Researchers at Duke University Medical Center in Durham, N.C., with the help of scientists in eight other countries, conducted two separate analyses on more than 10,000 patients and found that:
Living alone is not responsible for increased death rates among patients initially treated at a hospital for a heart attack. What does matter is the age of the patient, and since many elderly patients live by themselves, only a thorough analysis could weigh the relative impact of those two factors, the researchers said.
A patient's level of education and occupational status, on the other hand, significantly predict whether he or she will survive a heart attack over the long term. Investigators found that patients with the least education had a death rate one year after hospitalization that was more than five times higher than patients with more than 16 years of education.
The study, which included patients in the United States, Canada, United Kingdom, Germany, Australia, Sweden, Poland, New Zealand and Italy, was prepared for presentation Sunday at the 22nd annual congress of the European Society of Cardiology.
Dr. Conor O'Shea, a cardiologist at the Duke Clinical Research Institute who led the analysis, said the research offers several "take home" messages.
It's "good news" for patients who worry that living by themselves increases their health risk, he said.
But physicians need to be aware that education and job are risks factors for early death in patients who have suffered a heart attack, O'Shea said. Treatment that lessens stress or reduces the higher risk of mortality could help, he said.
Other studies have shown an association between socioeconomic status and higher rates of death from heart disease in general, but this study looked at whether that correlation persisted among patients who were being treated for a heart attack. It is the largest, most detailed study of its kind, and is also the first to include patients internationally, O'Shea said.
The analysis was based on information gathered during the worldwide GUSTO III clinical trial, which compared two different clot-busting drugs (t-PA and r-PA) in patients who had a heart attack. During the trial, which ran from 1995 to 1997, 10,838 patients completed information on their education and job status.
The research team, which includes investigators from the United States, Canada, Australia and England, examined that data as well as the clinical outcomes of patients to see if there was any correlation. They then "adjusted" those figures for important risk factors age, systolic blood pressure, heart rate and location of heart attack to see if education and occupation were independently important.
Both were found to be statistically significant factors in and of themselves, although the two factors "naturally" relate to each other, O'Shea said. "Laborers and homemakers in this study generally were less educated."
The investigators found that the death rate one year after hospitalization for patients with fewer than eight years of education was 19.8 percent, compared to 3.5 percent for those who had more than 16 years of education. Similarly, 5.1 percent of patients who described themselves as "laborers" died after a month, compared to 3.8 percent of patients in "management" positions.
"In all the countries we studied, it appears that a person's socioeconomic class determines how well they will do after a heart attack," O'Shea said. "Job status and educational level are both independent risk factors."
"Patients in this study who had fewer than eight years of education were older and had more diabetes," O'Shea said. "There is something about a person's level of education that leads to poorer outcomes. It could be an unlimited number of factors, including increased stress, poor understanding of the disease process and not making the necessary lifestyle changes needed to promote a better outcome."
The researchers did not determine whether a patient's level of insurance contributed to the results, although such information may only relate to U.S. patients, O'Shea said. "In Canada, Britain and Europe, health care is universally offered, so that shouldn't be a factor."
Previous research has made the case that "social isolation" can affect patient health in several ways. Living alone can promote bad health habits, such as poor diet, smoking and failure to follow medical advice. And it offers no buffer from depression and other psychosocial stresses.
Many of the studies suggesting that social isolation increases the long-term risk of cardiac mortality, however, were based on small numbers of patients and did not adequately consider "confounding factors" such as age and general health, O'Shea said. Because past research on this topic has been limited to patients in the United States and Canada, little is known about the importance of social isolation "in other areas of the world where people have substantially different lifestyles and cultural influences," he said.