A new study suggests divorce risk rises if the woman falls ill, but the same is not true if the husband gets sick.

"Married women diagnosed with a serious health condition may find themselves struggling with the impact of their disease while also experiencing the stress of divorce," Amelia Karraker, a researcher at the University of Michigan Institute for Social Research, said in a news release.

The researchers looked at 20 years-worth of data from 2,717 marriages, when the study started at least one member of each couple was over the age of 50.

The team looked at how "cancer, heart problems, lung disease and stroke," affected marriages in older couples.

Over 31 percent of the participants' marriage ended in divorce; during the study period more husbands than wives developed serious health problems.

"We found that women are doubly vulnerable to marital dissolution in the face of illness," Karraker said. "They are more likely to be widowed, and if they are the ones who become ill, they are more likely to get divorced."

The study did not conclude why divorce is more common in the face of female illness, but the researchers have a few ideas.

"Gender norms and social expectations about caregiving may make it more difficult for men to provide care to ill spouses," Karraker said. "And because of the imbalance in marriage markets, especially in older ages, divorced men have more choices among prospective partners than divorced women.

"We did not have information on who initiated divorce in this study. But it's important to keep in mind that in most cases, it's women who do so. So it could be that when women become ill and their husbands are not doing a very good job caring for them, they would rather that he just go and they rely on friends and family who will take care of them," she said.

The researcher believes policymakers should be aware of these statistics.

"Offering support services to spousal caregivers may reduce marital strain and prevent divorce at older ages," she said. "But it's also important to recognize that the impetus for divorce may be health-related and that sick ex-wives may need additional care and services to prevent worsening health and increased health expenditures."