Most older adults who are married name their spouses to make health care decisions for them should they become incapacitated and unable to convey their wishes to care providers. The common way to do this is through a durable power of attorney for health care, also called a health care proxy. But how accurate are spouses at knowing what their spouse would want to do in a particular situation?

Spouses are often surprisingly inaccurate, according to a new study by University of Wisconsin researchers. Reviewing responses from 2,750 married couples who participated in the 2004 Wisconsin Longitudinal Study, the researchers concluded that individuals often incorrectly identified their spouse’s care preferences.

For example, 28 percent of the study respondents incorrectly named their spouse’s preferences when presented with a hypothetical scenario involving the spouse being in great paid and having a low chance of survival. And 14 percent incorrectly identified their spouse’s preferences if the spouse were in minimal pain but were cognitively impaired.

The researchers found support for their hypothesis that respondents were projecting their own end-of-life preferences onto their partner. "[Respondents] did not distinguish well between their own preferences and the preferences of their spouses," the researchers concluded.

But the researchers found no support for the hypothesis that women are more accurate predictors of their spouse’s wishes than are men.

Among the researchers’ possible explanations for the apparent lack of knowledge of a spouse’s end-of-life treatment preferences were: a wish to avoid thinking about a partner’s death; an attempt to shield loved ones from potentially distressing concerns; efforts to conceal preferences from one another if they think the spouse will disapprove or change the preference; and the assumption that loved ones know them well enough to make the right choices.