Loneliness has long been associated with poor health, but researchers say they have new insights into the link between the two.
Although poor health can lead to isolation and loneliness, studies also suggest that loneliness can itself lead to poorer health.
Now, researchers say they have uncovered a mechanism for the latter relationship and discovered that loneliness can affect the levels of a handful of proteins associated with various illnesses and even death.
Professor Barbara Sahakian, co-author of the study at the University of Cambridge, said the World Health Organization had declared social isolation and loneliness a major problem in the world. “I think the message is that we need to start getting people to understand that this is part of a health issue, both for their mental health and their well-being, but also for their physical health, that they need to stay in touch with others,” she said.
Written in the journal Natureresearchers describe how they used data from more than 42,000 participants in the UK Biobank project to determine whether the 9.3% who reported being socially isolated and 6.4% who reported being alone had different blood protein levels than those who did not.
After taking into account factors such as age, gender, education level, smoking and alcohol consumption, the team discovered 175 proteins associated with social isolation and 26 proteins associated with self-reported loneliness, many of which overlapped. Most proteins were found at higher levels in people who reported social isolation or loneliness and are involved in inflammation, antiviral responses and the immune system.
The researchers then studied data that tracked the participants’ health over an average period of 14 years. “We found that about 90% of these proteins are linked to mortality risk,” said first author Dr. Chun Shen of Fudan University in China. Additionally, about 50% of the proteins were linked to cardiovascular disease, type 2 diabetes and stroke.
The researchers then used an approach known as Mendelian randomization to determine whether people with genetic variants associated with loneliness or social isolation were more likely to have higher levels of proteins of interest. They also looked at whether people with genetic variants meaning they had higher levels of these proteins were more likely to be socially isolated or lonely.
Assuming that these variants spread randomly in the population, the approach can help determine whether protein levels are a driver or effect of social isolation or loneliness.
The researchers found that none of the proteins seemed to cause social isolation or loneliness. However, loneliness influenced the levels of five proteins. “We found that these five proteins are linked to many inflammatory and metabolic markers,” Shen said.
Among other findings, these five proteins partly explained the association between loneliness and cardiovascular disease, stroke and mortality, with four of the five being associated with the volume of brain regions involved in emotional and social processes and the brain’s perception of the state of the body.
Shen said that while the effects were not large, they were significant, noting that levels of one of the proteins, known as ADM, could explain, on average, about 7.5 percent of the The association between loneliness and risk of four diseases and mortality.
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Professor Marko Elovainio, of the University of Helsinki, who was not involved in the work, said the study strongly supported previous research indicating that loneliness and – to some extent – social isolation were linked. to many physical health problems, probably due to systemic problems. stress-induced inflammatory processes.
“A significant contribution of this study is that it now elucidates the biological mechanism – the proteins – that could be responsible for the observed connections,” he said.
However, Elovainio suggested that stress-related behaviors, such as high alcohol consumption and low physical activity, might be an even bigger factor contributing to the health impacts of loneliness, and could also be at the the origin of some of the changes in protein levels reported in the study.
“The interesting question is how society should… reduce the health risks of loneliness, and if we want to focus on the mechanisms, behavior is probably an easier target than protein,” he said. he declared.