Socially isolated and lonely adults tended to have a biological age higher than their chronological age, according to a study of 309,746 UK Biobank participants published in Health Psychology. The association was strongest among people who experienced both forms of disconnection, and both isolation and loneliness were also linked to a higher risk of death during follow-up.
The researchers distinguished social isolation, an objective measure of limited contact and participation, from loneliness, the subjective feeling of lacking connection or someone to confide in. The two can occur separately: a person may have few social contacts without feeling lonely, or feel lonely while surrounded by others.
Participants were recruited between 2006 and 2010 and were followed for a median of 14.4 years, until July 2023. Their biological age was estimated using PhenoAge, a formula based on routine blood biomarkers. The researchers defined biological age acceleration as the difference between this estimate and a person’s chronological age.
After adjusting for demographic, socioeconomic, lifestyle and health factors, each one-point increase on the social-isolation scale was associated with 0.17 years of biological age acceleration. Each one-point increase on the loneliness scale was associated with 0.15 years. Compared with the least isolated participants, those in the most isolated group had an average gap of 0.33 years, while participants classified as lonely had a gap of 0.24 years compared with those who were not lonely.
The authors cautioned that these are modest average differences in an indicator of aging, not estimates of life lost or predictions for individuals. They also noted that the adjusted figures may understate the overall associations because factors such as smoking, sleep and chronic illness could be part of the pathways connecting social disconnection with health.
Among individual measures, living alone showed the strongest association with biological age acceleration. Not having someone to confide in was also linked to an older biological profile, with an association comparable in magnitude to often feeling lonely. The results point to emotional support as a dimension of social connection that may matter alongside the frequency of social contact.
When isolation and loneliness were considered together, people with high levels of both had the greatest biological age acceleration. Genetic risk for biological aging did not significantly change the association with social disconnection, but the risks appeared to add up: participants with both high genetic risk and high isolation or loneliness had larger age gaps than those with low genetic risk and minimal disconnection.
During follow-up, each one-point increase in the isolation score was associated with a 13.9% higher risk of death from any cause. Each one-point increase in the loneliness score was associated with an 8.9% higher risk. Both measures were also linked to higher rates of death from coronary artery disease and cancer. An exploratory analysis estimated that biological age acceleration accounted for a relatively small share of the associations between disconnection and mortality.
The findings do not establish that loneliness directly causes accelerated aging, or that increasing social contact can reverse it. Biological age was measured at one point, and the researchers said reverse causality cannot be ruled out: declining health could also make social participation harder or contribute to loneliness. The study relied on brief questionnaire measures, and its UK-based sample was predominantly of European ancestry.
The authors said further research should track biological age and social circumstances over time and test whether interventions that reduce loneliness or improve support produce measurable health effects.
Sources: PsyPost.