Years of being trapped in a bad marriage can literally break your heart, scientists have discovered.
A study found that people who have experienced decades of conflict with their spouse are more likely to develop heart disease than those in good marriages.
The finding was especially true for wives - possibly because women tend to internalise negative feelings more than men.
It suggests that relationship counselling should be directed at older couples as well as those starting out on the marital journey, say the US researchers.
Sociologist Hui Lui, from Michigan State University, said: "Marriage counselling is focused largely on younger couples. But these results show that marital quality is just as important at older ages, even when the couple has been married 40 or 50 years."
Dr Lui's team analysed five years of data from around 1,200 married men and women who were aged 57 to 85 at the start of the study.
All were participants in a major US investigation, the National Social Life Health and Aging Project which included questions on marital quality and looked at rates of heart attack, stroke, and high blood pressure.
The study, published online in the Journal Of Health And Social Behavior, found that bad marriages tainted by rows, criticism and demands were more harmful to the heart than good supportive ones were beneficial.
It also showed that the effect of marital quality on heart and artery disease risk became much stronger at older ages.
Over time, stress from a bad marriage may become more harmful because of declining immune function and frailty, the researchers believe.
Women, but not men, also appeared to experience a decline in marital quality as a result of suffering heart disease.
This may reflect the fact that wives are more likely to provide support and care to sick husbands than the other way round, said the scientists.
"In this way, a wife's poor health may affect how she assesses her marital quality, but a husband's poor health doesn't hurt his view of marriage," said Dr Liu.