A study by Iowa State University found a 6 percent higher probability of divorce for couples in which wives got sick compared with marriages in which wives remained healthy. However, a husband’s illness did not increase the risk for divorce.

Published in the March issue of the Journal of Health and Social Behavior, the study was conducted by Amelia Karraker, assistant professor of human development and family studies, and others. Karraker said the study didn’t spell out why the probability of divorce rose, but added that illness can add stress to a marriage.

For example, the healthy spouse is often the primary caregiver and may have to take sole responsibility of managing the household, Karraker said.

“There is a difference between feeling too sick to make dinner and needing someone to actually feed you.” Karraker said. “If your spouse is too sick to work, we know that financial strain is a major predictor of divorce in and of itself.”

Quality of care is another factor. Wives are generally less satisfied with the care from their husbands, Karraker said. That’s because men, especially older men, have not been socialized to be caregivers in the same way women have, and are less comfortable in that role.

Karraker and Kenzie Latham, an assistant professor at Indiana University-Purdue University Indianapolis, used data from the Health and Retirement Study, which does not indicate whether the husband or wife initiated the divorce. “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 relationship to begin with, and I’d rather be alone than be in a bad marriage.’ “