by Timothy Matthews and Line Jee Hartmann Rasmussen, The Conversation

Credit: Unsplash/CC0 Public Domain

Numerous studies have shown that social isolation and loneliness are associated with an increased risk of early death, on a scale comparable to other known risk factors such as smoking and obesity. This year, the US surgeon general declared social isolation and loneliness to be a significant public health concern.

But scientists are still trying to untangle the physical processes behind the relationship. Our team's recent study showed that social isolation and loneliness seem to be associated with higher levels of inflammation, which goes hand in hand with many health problems.

Researchers have argued that a desire for social connection –- and, conversely, an aversion to social disconnection –- is part of our evolutionary heritage. As a species, humans are not particularly big, strong or fast, but we are highly social, and our ancestors' chances of survival and reproductive success would have relied on the principle of safety in numbers. Being cut off from the social group represents a threat to your safety.

The immune system is one of several processes in the body that come into play under this scenario. A lone individual without the protection of a social group would be at greater risk of injury, and it therefore makes sense that the immune system would respond by preparing itself to battle off infection. This inflammatory response protects you in the short term. However, it is not ideal for your body to be in this stressed state for a prolonged period, and it could exert a toll on your physical health over time.

In our study published in November 2023 in the journal Brain, Behavior, and Immunity, we investigated the associations of social isolation and loneliness with markers of inflammation. Social isolation and loneliness are not the same thing. The former is an objective measure of your social connections, and the latter an emotion that can be experienced even when surrounded by other people. Both can have implications for mental and physical health.

In this study, we used data from three studies. Each of them had data on social isolation, loneliness and inflammation. Two of these studies followed participants from early childhood through to adulthood. This enabled us not only to test whether shortcomings in early social relationships foreshadowed increased inflammation later in life, but also to check whether any effects we found in one sample could be replicated in another sample.

We looked at three different markers of inflammation. Two of these, a protein made in the liver called C-Reactive Protein (CRP) and a type of protein involved in immune regulation called Interleukin-6 (IL-6) have been used extensively in medical research. The third, a protein called Soluble Urokinase Plasminogen Activator Receptor (suPAR), is a recently identified biomarker that research suggests is useful as an indicator of chronic (as opposed to acute) inflammation.

More information: Timothy Matthews et al, Social isolation, loneliness, and inflammation: A multi-cohort investigation in early and mid-adulthood, Brain, Behavior, and Immunity (2023). DOI: 10.1016/j.bbi.2023.11.022

Journal information: Brain, Behavior, and Immunity 

Provided by The Conversation 

This article is republished from The Conversation under a Creative Commons license. Read the original article.