A marriage is more likely to end in divorce when a wife is seriously ill, according to a new study.

The study, published in the Journal of Health and Social Behavior, found that a marriage was 6% more likely to end in divorce when a wife was diagnosed with serious illness than in marriages where the wife remained healthy. The study looked at data from more than 2,700 marriages with at least one partner over the age of 50. A husband’s illness did not affect the chances of divorce.

The study did not explain how illness may have led to divorce, but lead author Amelia Karraker said that illness can stress a marriage in many ways.

“Life-or-death experiences may cause people to re-evaluate what’s important in their lives,” said Karraker, an assistant professor at Iowa State University. “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.’”

Nearly a third of the marriages evaluated ended in divorce while nearly a quarter ended in the death of one spouse.

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Write to Justin Worland at justin.worland@time.com.