Living alone or simply feeling lonely may raise a person's risk for a decline in health, two new studies show.

The studies, published in the Archives of Internal Medicine, are some of the largest to date to support the idea that being isolated from friends and family affects the quality and length of a person's life.

For the first study, researchers followed nearly 45,000 adults aged 45 and older who had heart disease. About 19% of people in the study said they lived alone. People who were on their own were significantly more likely to die during the four years of the study than people who didn't live by themselves. And it appeared to be a phenomenon that crossed cultures since people in the study hailed from 44 countries.

The risk of dying was highest for middle-aged adults. People who were 45 to 65 years old and lived alone were 24% more likely to die during the study than people in the same age group who lived with spouses or roommates.

By way of comparison, having type 2 diabetes has been shown to increase a heart patient's risk of dying by about 40%, says researcher Deepak L. Bhatt, MD, MPH, a cardiologist at Brigham and Women's Hospital in Boston and an associate professor at Harvard Medical School.

"This should send up a little red flag that maybe this patient needs a little bit more attention," he says. "Maybe we need to be a little more careful that this patient really does go to fill their prescription," or gets to regular checkups or is able to buy and eat healthy meals, Bhatt tells WebMD.

Other researchers agree that loneliness is an important but perhaps underappreciated risk.

"If we can actually target this, I think we have the potential to make a lot of difference. By actually engaging with your patients and talking about this, it makes a better alliance," says researcher Carla M. Perissinotto, MD, MHS, a geriatrician and assistant clinical professor of medicine at the University of California at San Francisco.
Tracking the Impact of Loneliness on Health

In the second study, Perissinotto and her team followed more than 1,600 seniors older than 60 for six years, from 2002 to 2008. Study participants were asked if they felt left out, isolated, or if they lacked companionship.

Forty-three percent of people in the study said they felt lonely at least some of the time. Nearly 63% of people who reported loneliness were married or had a partner.

People who said they were lonely were 45% more likely to die during the study than people who didn't feel isolated. Nearly 23% of lonely people died, compared to 14% of people who said they didn't feel lonely. That risk remained even after researchers adjusted their data to remove the influence of other factors known to affect life expectancy, such as depression, income, age, and race.