People who are rarely or never visited by friends or family have a higher risk of dying, but a visit just once a month could ameliorate this, researchers from the University of Glasgow said.
The study, published in the journal BMC Medicine, identified five separate factors that each had an association with mortality, and found that some of these had interactive effects.
GPs seeking to identify people at risk should ask a variety of questions to identify those who are socially isolated, the researchers suggested.
Previous research has identified associations between all-cause mortality and both living alone and a sense of loneliness. But according to the authors, the combined impacts of different types of social interaction on premature death remained unclear. "A more detailed understanding of the health impact of different components of social connection, and their interactions, could help guide policy and interventions designed to increase and enhance social connectedness and improve related health outcomes," they stated.
Researchers Used Data From the UK Biobank
The study analysed data from 458,146 adults in the UK Biobank cohort, recruited between 2006 and 2010 at a mean age of 56.5 years. Participants completed a questionnaire when they were enrolled, and this included questions about five types of social interaction: whether they had someone close to confide in; whether they often felt lonely (subjective measures); how often they were visited by friends and family; whether they lived alone; and how often they participated in a weekly group activity (objective measures).
The researchers then linked these data to mortality registers.
After a median 12.6 years' follow-up, 33,135 (7.2%) of the participants had died, which included 5112 (1.1%) cardiovascular deaths.
All five types of social interaction were found to be independently associated with both all-cause and cardiovascular mortality. Overall, associations were stronger for the objective than the subjective measures, and lacking both types of social connection further increased the risk.
The strongest individual association was for people who were never visited by friends or family, for whom the risk of death was increased by 39%. Those who received visits at least monthly had a significantly lower associated increased mortality risk, implying a protective effect. However, more frequent visits brought no further benefit, suggesting a threshold effect, the team said.
Among people who never had such visits, the benefit of participating in weekly group activities was not observed, as the increased risk of death was comparable between those who did and did not join group activities (50% and 49%, respectively).
People Living Alone With No Visitors at Particularly High Risk
The protection afforded by monthly visits from friends or family was seen even in those not living alone. However, those who never had visits and who also lived alone had an even greater (77%) raised risk, and this dual lack of interactions potentially counteracted benefits from having other positive social connections, such as participating in weekly group activity, having a close confidant, or not often feeling lonely.
Lead author Dr Hamish Foster, clinical research fellow in general practice and primary care at the University of Glasgow, said in a pre-publication briefing: "The study shows the need to consider both types of social connection, as potentially addressing only one type in policy and interventions is unlikely to be sufficient."
Socially Isolated People May Have More Unhealthy Habits
While the study did not examine mechanisms, Dr Foster speculated that friends and family might offer particular types of support, such as helping to access health services, and perhaps higher quality relationships. Social disconnection and health outcomes could be linked through immune system effects or health behaviours. "It could be that people who are more socially isolated may have some more unhealthy behaviours, like smoking or high alcohol intake," he suggested.
Coauthor Jason Gill, professor of cardiometabolic health at the University of Glasgow, said that their results were adjusted for age, social deprivation, ethnicity, smoking, alcohol, physical activity, body mass index, comorbidities, and month of assessment. "Measures of social isolation and social connectedness are associated with risk of mortality independent of all these other factors that we know influence risk," he said.
The finding of a 'threshold' effect for friends and family visits, namely that visits that occurred more frequently than once a month "didn't give any additional benefits", was surprising and seemed "somewhat counterintuitive". The biggest risk seemed to be for people who are "very, very isolated and never ever see friends and family", he said.
Professor Gill noted that "social isolation and connectedness is much more complex than sometimes it's considered", and that a GP who asks a patient only a single question on social connections risks "missing a lot of the picture".
Future trials are needed to identify socially isolated people, to test interventions that could influence health outcomes, and to "design interventions to maximise the benefit", the researchers said.