Cardiac patients who feel lonely are at heightened risk of dying within a year of being discharged from hospital, reveals research published online in the journal Heart.
Loneliness should be prioritised in public health initiatives and regarded as a legitimate health risk in people who have a serious illness, conclude the researchers.
Previous research suggests that loneliness and poor social support are associated with a heightened risk of developing, and dying from, coronary artery disease.
But it's not clear if other types of heart disease might also be influenced by feelings of loneliness, and if living alone might be as influential as feeling lonely.
To explore this further, the researchers looked at the 1-year health outcomes of patients admitted to a specialist heart centre with either ischaemic (coronary) heart disease, abnormal heart rhythm, heart failure or valve disease, over the course of a year in 2013-14.
Most of them (70%) were men, and their average age was 66.
On discharge from the centre, 13,443 (53% of the total) completed validated questionnaires on their physical health, psychological wellbeing, and quality of life (Short Form 12; HeartQoL) and their levels of anxiety and depression (HADS).
They were also quizzed about health behaviours, including smoking, drinking, and how often they took their prescribed medicines. National data were used to find out if they lived alone or with other people.
Those who said they felt lonely were nearly three times as likely to be anxious and depressed and to report a significantly lower quality of life as those who said they didn't feel lonely.
One year later, the researchers checked national registry data to see what had happened to the patients' cardiac health, as well as how many of them had died.
They found that irrespective of the diagnosis, loneliness was associated with significantly poorer physical health after a year.
After taking account of potentially influential factors, including health behaviours, lonely women were nearly three times as likely to have died from any cause after a year as women who didn't feel lonely. Similarly, lonely men were more than twice as likely to have died from any cause.
The significant differences in risk between those who felt lonely and those who didn't, suggest that health related behaviours and underlying conditions can't fully explain the associations found, say the researchers.
Although living alone wasn't associated with feeling lonely, it was associated with a lower risk of anxiety/depression than in those who lived with other people.
And it was associated with a higher (39%) risk of poor cardiac health among men. Previous studies indicate that women have larger social networks than men, so separation, divorce, or the death of a partner may disadvantage men more, suggest the researchers, by way of an explanation for this particular finding.
This is an observational study, and as such, can't establish cause. Reverse causality may also be at play, as it's not clear whether the illness or the feelings of loneliness came first.
"However, the findings are in line with previous research, suggesting that loneliness is associated with changes in cardiovascular, neuroendocrine and immune function as well as unhealthy lifestyle choices which impact negative health outcomes," write the researchers.
There are indications that the burden of loneliness and social isolation is growing," they add.
"Furthermore, increasing evidence points to their influence on poor health outcomes being equivalent to the risk associated with severe obesity. Public health initiatives should therefore aim at reducing loneliness," they conclude.
Peer reviewed? Yes
Evidence type: Observational