According to researchers in the U.S. older couples who argue and row harm their hearts.
The researchers say the fighting results in artery disease both for wives and husbands.
It seems hardening of the coronary arteries is more likely in wives when they and their husbands express hostility during marital disagreements, and more common in husbands when either they or their wives act in a controlling manner.
The study by Professor Tim Smith and other psychologists from the University of Utah looked at 150 healthy, older, married couples, mostly in their 60s.
Professor Smith says they found that the levels of dominance or control in women or their husbands were not related to women's heart health, but women who are hostile are more likely to have atherosclerosis, especially if their husbands are hostile too.
He says in men, the hostility either their own or their wives hostility during the interaction also wasn't related to atherosclerosis, but their dominance or controlling behavior - or their wives dominance - was related to atherosclerosis in husbands.
Smith suggests that a poor or low-quality relationship, is a risk factor for cardiovascular disease.
The study began in 2002 and ended in 2005 and involved 150 married couples with at least one member between 60 and 70 years of age and the other one no more than five years older or younger.
The couples were recruited through newspaper advertisements and a polling firm and had no history of cardiovascular disease and were not taking medicine for it.
Each husband and wife was paid $150 to participate, and also received free of charge a $300 CT scan to look for calcification in their coronary arteries - the arteries that supply the heart muscle and that can cause a heart attack when clogged.
Smith says that in otherwise healthy people, calcification represents hardening and narrowing of the arteries that puts them at risk for later heart attack.
Each couple were instructed to pick a topic that was the subject of disagreements in their marriage, then, while sitting in comfortable chairs and facing each other across a table, they discussed the chosen topic for six minutes while they were videotaped.
Psychology graduate students coded the videotaped conversations so that "each comment that reflected a complete thought" was given a code indicating the extent to which it was friendly versus hostile, and submissive versus dominant or controlling.
According to Smith some of the marital discussions were calm and peaceful, but in some cases, the couples were so hostile, that the observers referred them to marriage counseling.
The researchers made the assumption that a couple's behavior during the discussion reflected their long-term pattern of behavior at home, if somewhat moderated.
Two days after their discussion, each couple underwent a CT scan of the chest at the University of Utah's Center for Advanced Medical Technologies to check each person's level of coronary artery calcification.
As the participants were all healthy, none of the "silent" atherosclerosis revealed by the CT scans amounted to a medical emergency, but says Smith there were people who had scores high enough to need to discuss it with their doctor, because statistically it placed them at a high risk of a coronary event.
In a nutshell the research reveals that hostility during marital disputes is bad for women's hearts, while controlling behavior during marital disputes is bad for men's hearts.
Smith says disagreements are an unavoidable fact of relationships, but it is clear that the way we talk during disagreements has an effect.
He says for men's heart health, couples need to find ways to talk about disagreements without trying to control each other, while for women's heart health couples need to find ways to have disagreements that are not hostile.
Spouses concerned about each other should avoid both hostility and controlling behavior during disagreements says Smith.
Previous research has indicated that close relationships are good for heart health and places people at less risk than feeling lonely and isolated does; but Smith says the new study suggests that the quality of those relationships is important.
Smith says a common factor is anger: wives' anger from feeling hostility or being subject to hostility; and husband's anger from experiencing or at least perceiving a challenge to their sense of control.
Smith does say as a word of warning, that people get heart disease for many reasons, and the most important form of protection for heart health remains - not to smoke, to exercise and follow a sensible diet.
But he says somewhere on the list should be, 'pay attention to your relationships'.
The findings were presented at the annual meeting of the American Psychosomatic Society, which deals with the influence of psychological factors on physical health.