Elderly people who are socially isolated and lonely may be at greater risk of early death, British researchers report.
Lack of social contact might be an even bigger risk factor than loneliness, they added. Why, however, isolation is such a powerful predictor of death isn't clear.
"Social contact is a fundamental aspect of human existence. The scientific evidence is that being socially isolated is probably bad for your health, and may lead to the development of serious illness and a reduced life span," said lead researcher Andrew Steptoe, director of the Institute of Epidemiology and Health Care at University College London.
There is also research suggesting that loneliness has similar associations with poor health, he said.
Lack of contact 'deadly'
"In many ways, social isolation and loneliness are two sides of the same coin. Social isolation indicates a lack of contact with friends, relatives and organisations, while loneliness is a subjective experience of lack of companionship and social contact," Steptoe said.
The investigators found that social isolation was a more consistent predictor of not surviving than was loneliness, and was related to greater risk of dying even after age and background health were taken into account, he said.
One expert said the findings were a little unexpected.
"You would think that loneliness would compound the risk for mortality, as opposed to just isolation -- it's a bit of a surprise," said Dr Bryan Bruno, acting chair of psychiatry at Lenox Hill Hospital in New York City, who was not involved with the study.
However, Steptoe explained, "Knowing about how lonely participants felt did not add to our ability to predict future mortality. This is not to say that loneliness is unimportant, or that we should not strive to reduce loneliness in older men and women," he said.
"But, we need to keep an eye on the social connections of older people, since maintaining social contacts among seniors and reducing isolation may be particularly important for their future survival," Steptoe added.
'A significant factor'
Bruno agreed that isolation is a significant factor in both reduced quality of life and mortality. "It is a difficult, challenging problem," he said.
"For my elderly patients, I often do a lot of education about the risk associated with being isolated and encourage them to spend as much time with other people as possible, whether it be family, friends or joining groups, community organisations or doing volunteer work," Bruno noted.
To look at the risks of loneliness and social isolation on dying, Steptoe's team collected data on 6 500 men and women aged 52 and older who took part in the English Longitudinal Study of Aging in 2004.
People who had limited contact with family or friends or community were classified as socially isolated. The researchers used a questionnaire to assess loneliness, which was described in background information in the study as a person's "dissatisfaction with the frequency and closeness of their social contacts, or the discrepancy between the relationships they have and the relationships they would like to have."
During nearly eight years of follow-up, 918 people died and social isolation and loneliness both predicted an early death.
Social isolation, however, increased the risk of dying regardless of one's health and other factors, while loneliness increased the risk of dying only among those with underlying mental or physical problems, the researchers found.
For more on social isolation, visit AARP.