‘Til death do us part' is a popular marital promise that couples are finding it increasingly difficult to keep, especially when ‘In sickness and in health' becomes a reality.

Nearly 6,300 divorces happen in the United States—every day. And, despite the perception that younger pairings are more likely to split up, new research indicates that when a chronic illness enters the picture, even partners who've been hitched for decades can succumb to separation and divorce.

After analyzing health and relationship data on more than 4,700 couples, a group of Iowa State University (ISU) researchers found that marriages in which an older wife has a stroke, or develops cancer, heart problems or lung disease are six percent more likely to end in divorce than marriages in which the wife remains healthy. Marriages in which the husband encounters one of these health problems, however, were no more likely to end in divorce.

"Illness may initiate changes to spouses' roles—in particular, increasing caregiving responsibilities for the healthy spouse—which can tax marital relationship dynamics," write study authors in an article in the Journal of Health and Social Behavior.

Which conditions cause the most martial stress?

Certain illnesses appear to be more taxing to a marriage than others.

Stroke, for instance, has a higher probability of leading to long-term disability and thus may put more prolonged stress on a married couple's relationship, say the ISU researchers. There is also the potential for cognitive impairment following a stroke, which further compounds the strain experienced by spousal caregivers and their loved ones.

Previous studies have also come to the conclusion that divorce rates tend to increase when one spouse becomes seriously ill.

Scientists from the Seattle Cancer Care Alliance and the Huntsman Cancer Institute at the University of Utah, School of Medicine found that women are six times more likely than men to get divorced or separated following a diagnosis of cancer or multiple sclerosis. The marriages of twenty-one percent of female patients in the study ended in separation or divorce, compared to just three percent of the marriages of male patients.

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Is divorce more likely when men are caregivers?

The stress of a loved one's illness, combined with the challenging role reversal that can occur when husbands must take care of their ill wives—a role that many men aren't properly socialized for—can create a perfect storm for marital misery. There's also the potential for a large financial burden, caused by increased medical bills and a loss of income that can occur when a husband has to quit his job or take time off from work to look after his wife.

"If your spouse is too sick to work, we know that financial strain is a major predictor of divorce in and of itself," points out Amelia Karraker, lead study author and assistant professor of human development and family studies at ISU, in a press release.

Though the data didn't reveal which gender was more likely to be the initiator of a divorce, Karraker also notes that wives who were being cared for by their husbands were often disappointed in their spouse's caregiving skills—which could also contribute to higher divorce rates. "It could be that women are saying, ‘You're doing a bad job of caring for me. I'm not happy with this, or I wasn't happy with the relationships to begin with, and I'd rather be alone than in a bad marriage,'" she says.

The health consequences of divorce

Being in a supportive marriage can have significant health benefits for both husbands and wives.

Studies have indicated that happily married individuals may have a decreased risk for developing cancer, dementia and pneumonia, as well as a greater likelihood of engaging in healthy lifestyle behaviors. Divorce and unhappy marriages, on the other hand, have been associated with higher stress, a weakened immune system, and an increased risk for depression, heart disease and diabetes.

Unfortunately, when a chronic illness threatens to break apart a marriage, it not only impacts the physical and mental well-being of the couple, but their social health as well. "I think the research shows the potential vulnerabilities for people in society who are sick," Karraker says. "People in poor health may have less access to beneficial social relationships, which in turn can compromise their health further."

Support for spousal caregivers

Spousal caregivers make up about 17 percent of the family caregiver population, according to a recent AgingCare.com survey. This unique population of caregivers and care recipients requires a unique kind of support—one that focuses on helping husbands and wives navigate the nuances of a relationship that has been altered by illness.

There's no better source of information and inspiration for spousal caregivers than their peers—other men and women faced with the challenges of caring for a beloved life partner. Spousal caregivers offer each other countless words of wisdom on the AgingCare.com Caregiver Support Groups:

"The person we shared our lives with...even if it was just a short while....is not the same as a parent. A spouse is a partner, a friend...to see that person change and become a stranger is so hard."

"It is hard to except (for me anyway) that my husband will be dying in the near future and to watch his memory go as well. All I can say to everyone else is that we are not alone in this path we have taken on. One day at a time is the only thing that keeps me going and remembering that it is the disease not the person. Hang in there it is hard but survivable."

"I always hate it when people tell me I'm a saint or an angel. No, I'm a human being doing my best, which is often pretty darn good but never perfect. Fortunately we do not have to be saints to do a good job. And fortunately perfection is not required."

"The relationship does change at some point from one of great, passionate love to one of caring, friendship, and compassion. And, of course, by degrees I am assuming more and more control. Gradually, though, I am learning to take things as they come, and keep reminding myself that it is indeed the disease, not the person. And I make it a point to take good care of myself, as well, so that I can take care of him."

"Try to focus on what you can do and not what you can't. Put one fire out at a time. You can only do your best and that is all you can do. If you got married for Love that is what you need to focus on. That Love should be your strength."

Find support and help other spousal caregivers by joining the conversation.