A recent study has found that living alone and experiencing childhood social isolation are associated with increased levels of inflammation in adults. Published in Brain, Behavior, and Immunity, the research highlights the significant impact of social connections on physical health.
The motivation behind this study stemmed from a growing body of evidence indicating the crucial role of social relationships in health and longevity. Prior research has consistently shown that social connections are not just beneficial but essential for maintaining good health.
A particularly intriguing aspect is the potential connection between social isolation and increased inflammation, a key factor in various health issues. Researchers embarked on this study to explore how different aspects of social relationships, specifically living alone, childhood social isolation, and loneliness, relate to inflammation, which is a known risk factor for various chronic diseases.
“There is now abundant evidence that both social isolation and loneliness are risk factors for early mortality,” said study author Timothy Matthews, a lecturer in psychology at the University of Greenwich. “We were interested in studying potential processes through which these experiences – particularly when experienced in childhood – might become biologically embedded. Based on the literature on other stressful childhood experiences, we hypothesized that inflammation was a plausible candidate.”
Conducted across three diverse cohorts, the study involved a large sample size to ensure robust results. In Denmark, the research included 6,144 acutely admitted medical patients. In New Zealand, the study analyzed data from 881 participants in a birth cohort study, and in the United Kingdom, it involved 1,448 participants from a twin cohort.
The study used both direct and proxy measures of social isolation and loneliness. Living alone was used as a proxy for social isolation in the Danish cohort. In the New Zealand and UK cohorts, childhood social isolation and adult loneliness were assessed through detailed questionnaires and interviews.
The researchers measured inflammation using three different biomarkers: C-Reactive Protein (CRP), Interleukin-6 (IL-6), and the novel marker soluble urokinase plasminogen activator receptor (suPAR).
In Denmark, patients who were living alone showed significantly higher levels of all three inflammation markers compared to those not living alone. However, after adjusting for factors like age, sex, body mass index, and smoking, only higher suPAR levels remained significant.
“We measured inflammation using three different biomarkers,” Matthews told PsyPost. “Two of these, CRP and IL-6, are very widely used, while the third, suPAR, is a relatively new marker which we believe is useful for studying systemic chronic inflammation. Of the three, social isolation was most consistently associated with suPAR.”
In New Zealand, participants who experienced childhood social isolation or loneliness at age 38 had higher levels of all three biomarkers at age 45. These associations remained significant for suPAR even after accounting for other influential factors.
In the UK study of young adults, childhood social isolation was associated with higher levels of these biomarkers at age 18, but only the suPAR levels remained significant after adjustments.
These results collectively suggest that living alone and experiencing social isolation during childhood are more consistently associated with increased inflammation, particularly indicated by the suPAR marker, than loneliness. Social isolation refers to the objective lack of social contacts and interactions with others, while loneliness is a subjective feeling of being alone or disconnected from others, regardless of the actual number of social contacts one has.
“A key finding is that children who are socially isolated may show signs of chronic inflammation many years later in adulthood, which in turn could signal risk for conditions such as heart disease and diabetes,” Matthews explained. “Therefore, a take-away point is that we should act early to support children who end up on the fringes of their peer group.”
Looking ahead, the findings open several avenues for future research. Further studies could explore more comprehensive and direct measures of social isolation and loneliness and include longitudinal designs to better understand how these social factors affect inflammation over time.
Another important direction would be to investigate the biological mechanisms underlying these associations, such as the role of the hypothalamic-pituitary-adrenal axis, which could provide deeper insights into the interaction between social factors and physical health.
“While we took care to control for potential confounding variables, such as smoking and body mass index, further work can be done to advance causal hypotheses,” Matthews said. “Incorporating measures of inflammation in intervention studies is one way this could be taken forward.”
“A strength of this study is that we were able to replicate the findings in multiple samples, including two population-representative cohort studies that have followed participants from childhood through to adulthood.”
The study, “Social isolation, loneliness, and inflammation: A multi-cohort investigation in early and mid-adulthood“, was authored Timothy Matthews, Line Jee Hartmann Rasmussen, Antony Ambler, Andrea Danese, Jesper Eugen-Olsen, Daisy Fancourt, Helen L. Fisher, Kasper Karmark Iversen, Martin Schultz, Karen Sugden, Benjamin Williams, Avshalom Caspi, and Terrie E. Moffitt.
