In the study of 1,981 middle-age heterosexual couples in the US, researchers found that people with happy spouses were much more likely to report better health over time.
This occurred above and beyond the person's own happiness, researchers said.
"This finding significantly broadens assumptions about the relationship between happiness and health, suggesting a unique social link," said William Chopik, an assistant professor of psychology at Michigan State University.
"Simply having a happy partner may enhance health as much as striving to be happy oneself," said Chopik, principal investigator of the study.
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He said there are at least three potential reasons why having a happy partner might enhance a person's health, irrespective of one's own happiness.
Happy partners likely provide stronger social support, such as caretaking, as compared to unhappy partners who are more likely to be focused on their own stressors, researchers said.
Happy partners may get unhappy people involved with activities and environments that promote good health, such as maintaining regular sleep cycles, eating nutritious food and exercising, they said.
"Simply knowing that one's partner is satisfied with his or her individual circumstances may temper a person's need to seek self-destructive outlets, such as drinking or drugs, and may more generally offer contentment in ways that afford health benefits down the road," Chopik said.
The study examined the survey information of couples aged 50 to 94, including happiness, self-rated health and physical activity over a six-year period.
The results showed no difference between husbands and wives in the study.
Eighty-four per cent were white, 8 per cent were African-American, and 6 per cent were Hispanic.
The study was published in the journal Health Psychology.