The study, published in journal the Archives of Internal Medicine, found that loneliness increased the risk of death by almost 10 per cent in adults aged 60 years and above.
Feeling lonely was also linked with functional decline and a reduction in day-to-day activities, researchers at the University of California at San Francisco have found.
The researchers, led by Dr Carla Perissinotto, believe their findings could important public health implications.
"Loneliness is a common source of suffering in older persons. We demonstrated that it's also a risk factor for poor health outcomes including death and multiple measures of functional decline," the Daily Mail quoted the team as saying.
"Assessment of loneliness is not routine in clinical practice and it may be viewed as beyond the scope of medical practice. However, loneliness may be as an important of a predictor of adverse health outcomes as many traditional medical risk factors.
"Our results suggest that questioning older persons about loneliness may be a useful way of identifying elderly persons at risk of disability and poor health outcomes."
For their study, the team examined the relationship between loneliness and risk of functional decline and death in older individuals in a study of 1,604 participants in the US.
The participants, with an average age of 71, were asked if they felt left out, isolated or a lack of companionship. Of them, 43.2 per cent reported feeling lonely, which was defined as reporting one of the loneliness items at least some of the time, the researchers found.
Loneliness was associated with an increased risk of death over the six-year follow-up period, 22.8 per cent compared to 14.2 per cent.
The team also found isolated participants were twice as likely to experience a decline in daily activities with 24.8 per cent adversely affected compared to 12.5per cent of peers.
Meanwhile, 40.8 per cent of lonely people struggled with the stairs compared to 27.9 per cent of their more social peers, the study found. (More)