Loneliness linked to poor health through effect on protein levels, research suggests

Loneliness has long been linked to poor health, but researchers say they have new insights into the link between the two.

While poor health can cause people to become isolated and lonely, studies have also shown that loneliness itself can lead to poorer health.

Now researchers say they have discovered a mechanism for the latter relationship. ​​The discovery that loneliness can affect the levels of a handful of proteins linked to various diseases and even death.

Professor Barbara Sahakian, co-author of the study from the University of Cambridge, said the World Health Organization has declared social isolation and loneliness a major problem in the world. “I think the message is that we have to start getting people to realize that it 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 connected to other people. she said.

Writing in the journal Naturethe researchers describe how they used data from more than 42,000 participants in the UK Biobank project to investigate whether the 9.3% who reported social isolation and 6.4% who reported loneliness had different levels of proteins in their blood compared to those who didn’t.

After taking into account factors such as age, gender, education level, smoking and alcohol consumption, the team found 175 proteins linked to social isolation and 26 proteins linked to self-reported loneliness, many of which overlapped. Most of the 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 examined data that tracked participants’ health over an average of 14 years. “We found that about 90% of these proteins are associated with the risk of mortality,” said Dr. Chun Shen, the study’s first author, from Fudan University in China. In addition, 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 see whether people with genetic variants associated with loneliness or social isolation were more likely to have higher levels of the proteins they were interested in. They also looked at whether people with genetic variants that meant they had higher levels of these proteins were more likely to be socially isolated or lonely.

Assuming these variants are randomly distributed across the population, the approach could shed light on whether the levels of the proteins are a driver or an effect of social isolation or loneliness.

The researchers found that none of the proteins appeared to cause social isolation or loneliness. However, loneliness affected the levels of five proteins. “We found that all five of these proteins are associated with numerous inflammatory and metabolic markers,” Shen said.

Among other findings, these five proteins partially explained the association between loneliness and cardiovascular disease, stroke and mortality, with four of the five linked to the volume of brain areas involved in emotional and social processes and the brain’s perception of the condition of the body.

Shen said that while the effects were not large, they were significant. In doing so, he noted that levels of one of the proteins, known as ADM, explained on average about 7.5% of the association between loneliness and the risk of four diseases and mortality.

Prof. Marko Elovainio of the University of Helsinki, who was not involved in the work, said the study strongly supported previous research showing that loneliness and – to some extent – social isolation were linked to numerous physical health problems, possibly due to systemic problems. inflammatory processes caused by stress.

“An important contribution of this study is that it now elucidates the biological mechanism – proteins – that may be responsible for the observed compounds,” he said.

However, Elovainio suggested that stress-related health behaviors, such as heavy alcohol consumption and low physical activity, could be an even more important factor contributing to the health effects of loneliness, and could also underlie some of the protein level changes seen in the research are marked.

“How society should reduce the health risks associated with loneliness is the interesting question, and if we want to focus on the mechanisms, behavior is probably an easier target than proteins,” he said.