While it is known that an unhappy marriage leads to broken hearts, it may come as a surprise that a broken heart can manifest into something far more real than mere emotional distress. A new study published this weekclaims that a bad marriage can in face increase the risk of heart disease, especially in women.

Researchers from the Michigan State University investigated the connection between marriage quality and heart health over an extended period of time. The study was funded by the National Institutes of Health, and is reputed to be among the first of its kind.

Researchers analyzed five years of data from 1,200 married U.S. women and men of ages 57 to 85  to determine their heart health as shown by a range of factors including incidences of heart attacks and strokes and measurements of cholesterol levels.

The participants were part of a U.S. investigation called the National Social Life Health and Aging Project. In followup sessions, researchers questioned the wives and husbands on how close they felt for their current mate, how demanding they felt their spouses were, and how happy they thought their marriages were.

The researchers said that individuals with spouses who were more demanding or excessively critical were found to be more likely of developing heart diseases than those with supportive life partners. They also found that with age the harmful impact on the health of the heart because of a bad marriage increased. The effect of marital quality on the heart became much stronger with age. The same happens with the risk of artery diseases probably because the stress related to marriage might be able to stimulate more intense and more cardiovascular responses because of decline of the immune function and fragility as people age.

"Married people seem healthier because marriage may promote health," said sociologist and lead study investigator Hui Liu. "But it's not that every marriage is better than none. The quality of marriage is really important." Liu stressed that both good and bad marital qualities were taken into consideration in the study, since "some people really love each other and have a lot of happiness, but at other times they may have a lot of arguments."

Women were also found to be more affected by the bad marriage and likely suffer more health problems. They also found that heart problems tend to lead to a decline in marriage quality only for women. This corresponds to the belief that wives are more likely to support and take care of sick men, while husbands are less likely to do the same for their wives.

"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," Liu explained. "Marriage counseling 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,"

As to why females felt the effects of a bad marriage more, Liu said women are more inclined to internalize feelings and be more sensitive than their male partners in a relationship.

The study also indicated that when women were stricken with heart disease, it actually lowered the quality of a marriage, but not so when men were sick.

The research team concluded that being in an unhappy marriage caused stress, which in turn can be harmful to cardiovascular health - and the negative impact was even more pronounced in women and older adults over the long haul.

"It's not like you have contact with your spouse and the next day you have heart disease," said Liu. "It really takes time. That may explain why it's stronger for older people. Your body will remember the effect."

The study was published in the Journal of Health and Social Behavior.