Married people have better survival rates after coronary bypass surgery than single people, researchers at the University of Rochester found in a new study.

While the study, released Monday, does not prove that being married causes patients to survive longer, it shows a strong relationship between the two. Specifically, married people are three times more likely than unmarried people to be alive 15 years after bypass surgery.

Intriguingly, women benefited only if their marriage was satisfying, whereas men benefited in satisfying and unsatisfying marriages alike. In satisfying marriages, however, women benefited even more strongly than men.

While unhappy marriages provide virtually no survival bonus for women, satisfying unions increase a woman's survival rate almost fourfold, according to a University of Rochester press release.

The study followed 225 patients who had bypass surgery between 1987 and 1990. One year after surgery, patients who were married were asked to rate their satisfaction with their marriage. After 15 years, 83 percent of women in satisfying marriages were alive, compared to only 28 percent of women in unhappy marriages and 27 percent of unmarried women. Men in satisfying relationships also had an 83 percent chance of survival, while men in unsatisfying marriages had a 60 percent chance and unmarried men a 36 percent chance.

If marriage does in fact lead to higher survival rates, it would probably be because spouses tend to encourage healthy living habits, like exercising more or quitting smoking, the press release said. Also, earlier research has shown that that people in happy marriages had less inflammation that could lead to heart disease.

There is something in a good relationship that helps people stay on track, the lead author of the study, Kathleen King, said.