The University of Michigan study challenges previous studies have documented negative health effects of family caregiving.

"The current results show that it is time to disentangle the presumed stress of providing help from the stress of witnessing a loved one suffer," lead author Stephanie Brown said in a statement.

Brown and colleagues reviewed seven years of data from the University of Michigan Health and Retirement Study. The analysis focused on 1,688 couples, all of whom lived on their own and were age 70 or older.

In 1993, the couple reported on how much each received help from the spouse in everyday activities such as eating, dressing and bathing and managing money.

The study, published in Psychological Science, found about 81 percent said they received no help at all from their spouse.

Over the course of the study, 909 people died and after controlling for health, age, race, gender, education, employment status and net worth, the study found spouses who provided at least 14 hours of care a week to their spouses were significantly less likely to have died during the study period than those who provided no spousal care.