The study shows that, compared to married heart disease patients, being unmarried was associated with a higher risk of dying.
Scientists have known that divorcees are at increased risk for death in general.
Few studies have evaluated the relationship between adverse cardiovascular outcomes and marital status in patients with known or suspected coronary artery disease.
The study, published in the Journal of the American Heart Association, of 6,051 patients, with an average age of 63 undergoing cardiac catheterisation for coronary artery disease, is the first to show poor outcomes specifically among those who were divorced, separated, widowed or never married.
Patients were followed for 3.7 years.
Researchers found that compared to married patients, being unmarried was associated with a 24 per cent higher risk of death from any cause; a 45 per cent higher risk of death from cardiovascular disease; and a 52 per cent higher risk of cardiovascular death or heart attack.
The risk of cardiovascular death or heart attack was 40 per cent higher for those who were never married; 41 per cent higher for those who were divorced or separated; and 71 per cent higher for those who had been widowed.
Lead researcher Professor Arshed Quyyumi, of Emory University in the United States, said: “I was somewhat surprised by the magnitude of the influence of being married has on heart patients.
“Social support provided by marriage, and perhaps many other benefits of companionship, are important for people with heart disease.”
He said the unmarried people in the study were more likely to be female and black, have high blood pressure, heart failure, or high cholesterol and less likely to be smokers compared with the married patients.
The researchers suggest that it may be important to consider marital status in treating coronary artery disease patients.
Psychological conditions associated with being unmarried and potentially more aggressive follow-up and therapy needs to be considered in future studies.
Patients with severe heart valve damage, anemia, congenital heart disease, cancer or active inflammatory disease were excluded from the study.
Marital status was determined from self-administered questionnaires. Divorced and separated people were combined into one group for the study.
Prof Quyyumi, said the findings can’t be applied to the general population without cardiovascular disease.