Elderly men and women caring for spouses who have been hospitalized for serious illness are themselves at increased risk of dying prematurely, especially in the first few months afterward, researchers are reporting today.

The study, the most comprehensive to examine the health risks of caring for an ill partner, found that the risk to spouses was highest when the hospitalization was for a chronic, disabling illness like dementia or congestive heart disease, and lowest when it was for illnesses like terminal cancer. 

The study, appearing today in The New England Journal of Medicine, confirms what psychologists, gerontologists and public health researchers have long known: that the stress of caring for a family member, and especially a husband or wife, is itself a public health problem, bringing anxiety and endless chores at a time of life when people may be trying to manage their own health problems. 

"It's a very exciting article, and the finding of increased risk associated with hospitalization is new, suggesting there might be something else besides a loss of social support" that increases the health risks for care givers, said Joan Bloom, a professor in public health at the University of California, Berkeley, who was not involved in the study. 

Dr. Bloom said the article would challenge researchers to learn more about how exactly the stress of providing care raised the mortality risk. 

In the study, Dr. Nicholas Christakis of Harvard Medical School and Paul Allison, a sociologist at the University of Pennsylvania, studied the medical records of 518,240 married couples enrolled in Medicare in 1993, most of whom were over 70. They found that losing a spouse increased the risk of dying prematurely by 20 percent, to 6.7 percent from 5.6 percent for men, and to 3.1 percent from 2.6 percent for women, in the first year of the study. But having a husband or wife hospitalized also increased their mortality, by about a quarter as much as being widowed did. The researchers examined nine years of records of the couples.

"What it shows is that people are interconnected, and their health is interconnected, and seeing a person you love suffer, seeing them ill, harms you," Dr. Christakis said. 

Separating out the effects of specific diseases, that study found that fatal illnesses, like terminal cancer, were the least burdensome, perhaps because they are well defined, often predictable and tend not to rob people of their lucidity until the very end, the researchers said. 

The diseases that caused the highest increase in risk for spouses who were providing care were psychiatric disorders and dementia: men whose wives were hospitalized for these diseases had about a 20 percent increased risk of dying themselves - the same risk associated with being widowed. Women caring for similarly afflicted husbands were at a higher risk of dying than if their husbands died. 

It is no surprise, experts say, that the illnesses that produce the most stress are those, like dementia, that seem to leach away a loved one's intelligence and personality while leaving them physically functional for years - there but not there - a process that some have called ambiguous loss. 

"When something like this happens and you are alone, you're the only one, it's a very, very draining situation," Dr. Bloom said. 

The researchers said they were now analyzing the medical records to find out more about what caused the deaths of the caregivers. Stress-related illnesses appear to have been more common in the first months after a spouse fell ill, and loss of social support may have been more of a factor later on, they said.