People who are socially isolated are more likely to die prematurely, regardless of their underlying health issues, according to a study of the elderly British population.
The findings, published online Monday in the Proceedings of the National Academy of Sciences, showed that when mental and physical health conditions were factored out, the lack of social contact continued to lead to early death among 6,500 men and women tracked over a seven-year period.
"They're dying of the usual causes, but isolation has a strong influence," said study author Andrew Steptoe, an epidemiologist at University College London.
The study also appeared to diminish the role that subjective feelings of "loneliness," as opposed to the lack of social contact, may have on a person's life span. Both lead to higher mortality risks, the study noted, but the effect of feeling lonely diminishes once demographic and health factors are taken into account.
Regardless of the distinction, the study reinforces the need to increase social support for the elderly, even as it adds to debate over the intertwined effects of social contact and feelings of loneliness in old age. A similar look at retired Americans in 2012 reinforced multiple studies that link loneliness to numerous illnesses, including heart trouble and high blood pressure.
Both studies come as British and U.S. populations have become more solitary. People living alone compose more than a quarter of U.S households, and the proportion of Americans who said they had no one to talk to about important matters grew from 10% in 1985 to 25% in 2004, according to authors of the British study. A 2010 European survey revealed that more than a quarter of Europeans aged 50 and over reported that they met friends, colleagues or family less than once a month.
Separating the effects of loneliness from those of isolation, however, has not been easy for those who study rates of illness and death. While isolation can be measured directly — by how many friends you have or how often you have contact with family — loneliness is more subjective, measured through survey questions about whether social needs and expectations are being met.
Anyone familiar with Henry David Thoreau knows that isolation does not necessarily lead to loneliness, while the story of Marilyn Monroe shows that a strong social life can still leave you lonely.
A 1992 study of 2,000 heart patients suggested that having a confidant was more important than social links alone. It showed that relative mortality nearly tripled among those who had neither a partner nor a confidant, compared with those who had confidants (whether they were married or unmarried), according to the author of that study, Redford Williams, director of the behavioral medical research center at Duke University.
"There is something about not having social support — that is not acting through loneliness, nor through other health problems — that is contributing to mortality," Williams said.
Confusing the picture are studies that show loneliness leading to poor health, including higher blood pressure, heightened reaction to stress and altered immune responses, all of which can lead to higher mortality risk.
"Unfortunately in our study, we can't tell which comes first," Steptoe said. "We did know that lonely people did have more illnesses."
Last year's report on loneliness, based on the U.S. Health and Retirement Study, showed that loneliness appeared to increase mortality risk over a six-year period, an association that could not be attributed to social relationships or health behaviors, such as smoking and drinking.
Isolation may encourage poor lifestyle choices such as smoking, inactivity and unhealthy diets, which factor into mortality rates, said John Cacioppo, director of the Center for Cognitive and Social Neuroscience at the University of Chicago, an author of the 2012 study. He suggested that the British tradition of a "stiff upper lip" may mean Britons who live alone "are less likely to admit to feeling lonely than are residents of the U.S."
Nonetheless, Cacioppo said, "Whether or not loneliness predicts mortality in the UK, it most certainly does predict lower well-being, increased depressive symptomatology, and decreased cognitive functioning in older adults in the UK as well as in the U.S. This makes it important to address in the UK whether or not it predicts mortality."
Richard Suzman, director of the National Institute on Aging's division of behavioral and social research, said: "It may be that loneliness and ill health are much more entangled. The question is, does loneliness lead to ill health or is it that when you get ill you get more lonely — you don't get out, or people don't visit as much."
The National Institute on Aging, part of the National Institutes of Health, funded both the British study and last year's report on U.S. retirees.
Loneliness and isolation "should get lots of attention because they may be as important, as joint factors, as smoking," Suzman said.
Studies that involve interventions would help separate the different effects of loneliness and isolation, he added. "Isolation wins out this time, but I'd want an experiment to verify that."