As we learned earlier today, marriage may make you fat, but a happy union may also help you live longer, according to a new study of heart patients. Patients who were married when they underwent coronary artery bypass surgery were more than twice as likely to survive for 15 years, compared with unmarried patients, and those who were in happier marriages were more likely to live longer.
Researchers at the University of Rochester followed 225 bypass patients of both genders who had surgery between 1987 and 1990. The day before surgery, researchers asked about the patients’ marital status; one year later, the participants were asked to rate their relationship satisfaction.
Then, using hospital data, the researchers assessed who was still alive 15 years later. Overall, 55% (124 patients) survived 15 years: 61% of the married patients and 30% of the singletons. The researchers adjusted for other factors associated with cardiovascular health, such as age, sex, education, smoking and depression.
The survival rates were even starker when parsed by marital satisfaction and gender. Fully 83% of men and women who said they had happy marriages were alive 15 years later, compared with 27% of women and 36% of men who were single. But among the unhappily married, only 29% of women had survived, compared with 60% of men.
In other words, women who reported dissatisfaction in their marriages had no survival benefit over women who had no marriage at all. The findings fall in line with previous studies suggesting that while men tend to benefit from marriage in general, women may benefit only when the unions are happy.
“Other research has shown that women are more physiologically sensitive to relationship distress than men, so an unhappy marriage can take a greater toll on their health,” said Harry Reis, one of the study’s authors and a professor of psychology at the University of Rochester, in a statement.
Still, the differences between married and unmarried women shrunk when the researchers adjusted for age, and there may have been too few women in the study sample — just 52, versus 173 men — to see a real effect.
There were other limitations. It’s possible that patients who were more likely to report relationship satisfaction were also those who had a sunnier disposition in general, and that could have contributed to better health outcomes. It’s also possible that healthier and happier people are more likely to get married in the first place.
Although the research didn’t explain why marriages may be helpful for long-term survival after bypass surgery, the researchers theorized that it has to do with social support. Spouses tend to encourage each other to make healthy lifestyle choices, like eating right, exercising and quitting smoking. A particularly happy relationship may provide even more spousal support — and a powerful impetus to stay alive.
The good news is that any effect on longevity that’s attributable to marriage probably applies to all long-term, supportive relationships, not just legal unions. “I don’t think it has to be [a] traditional marriage,” Kathleen B. King, professor emeritus in the School of Nursing at the University of Rochester and lead author of the study, told Health.com.
The study was published Monday online by the journal Health Psychology.
Meredith Melnick is a reporter at TIME. Find her on Twitter at @MeredithCM. You can also continue the discussion on TIME’s Facebook page and on Twitter at @TIME.