People who experience loneliness and a lack of social contacts have, on average, a higher biological age compared with their peers. At the same time, the combination of social isolation and emotional loneliness is associated with the most pronounced signs of accelerated aging and an increased risk of premature death.
This conclusion was reached by an international group of researchers led by scientists from China's Central South University, who analyzed data from 309,746 residents of the United Kingdom.
The results of the study, Social Isolation, Loneliness, and Biological Aging Acceleration, were published in the scientific journal Health Psychology, while the specialized publication PsyPost presented a detailed review of the research on November 4.
Loneliness is associated with an increase in biological age of several months
The researchers used data from the British biomedical database UK Biobank. The average age of the participants was 56.4 years, and 54% of them were women.
The participants' health status and mortality were monitored for an average of 14.4 years. Baseline information on health status and social contacts was collected between 2006 and 2010, while survival data were tracked until July 2023.
Biological age was assessed using the PhenoAge method, which makes it possible to determine the physiological condition of the body based on blood biomarkers, including indicators of inflammation and internal organ function.
Unlike chronological age, which is determined by the number of years a person has lived, biological age reflects the condition of the body and may differ among people born in the same year.
After accounting for socioeconomic factors, lifestyle and existing diseases, the scientists found that people with the most pronounced social isolation had a biological age that was, on average, 0.33 years, or approximately four months, higher than expected.
Among participants who experienced pronounced loneliness, the corresponding difference was 0.24 years, or about three months.
This does not mean a reduction in life expectancy by the specified number of months, but rather a statistical difference in biological age indicators.
The most pronounced deviations were observed among people who experienced both social isolation and loneliness.
The absence of a close person may be particularly significant
During the study, the scientists distinguished between two concepts: social isolation and loneliness.
Social isolation was assessed using objective indicators, including living alone, infrequent meetings with friends and relatives, and a lack of regular participation in group activities.
Loneliness was defined as the subjective feeling of insufficient emotional closeness and support.
The analysis showed that living alone was associated with an increase in estimated biological age of 0.27 years. Having no one to confide in corresponded to an increase of 0.22 years, while not participating in regular social activities was associated with an increase of 0.17 years.
At the same time, frequently experiencing a subjective feeling of loneliness corresponded to an increase of 0.14 years, while infrequent meetings with relatives and friends were associated with an increase of 0.09 years.
Thus, the quality of social relationships may be no less important than the number of contacts with other people.
The researchers pay particular attention to the role of emotional support. A person may maintain a wide circle of social connections while still experiencing loneliness because of a lack of trusting relationships.
Social isolation is associated with an increased risk of death
The scientists additionally examined the relationship between social isolation, loneliness and all-cause mortality.
According to the findings, a one-point increase in the social isolation score on the three-point scale used in the study corresponded to a 13.9% increase in the relative risk of death from any cause.
A one-point increase in the loneliness score on a separate two-point scale was associated with an 8.9% increase in the risk of death.
A statistical association was also found between both factors and the risk of death from coronary heart disease and cancer.
At the same time, the researchers established that accelerated biological aging explains only a small part of the observed association between social isolation and mortality.
According to the statistical model, changes in biological age accounted for approximately 5.2% of the association between social isolation and mortality and 7.2% of the corresponding association for loneliness.
This suggests that social isolation may be related to health through several mechanisms, including chronic stress, behavioral patterns, physical activity and inflammatory processes.
Genetic predisposition increases the combined risk
An important part of the research was the study of the interaction between social factors and genetic predisposition to accelerated aging.
The researchers calculated polygenic risk scores for the participants based on characteristics of their DNA.
It turned out that genetic and social factors act largely independently of one another, although their effects may be cumulative.
Among people with a high genetic predisposition to accelerated aging and pronounced social isolation, biological age was approximately 1.7 years higher than expected compared with participants whose risk indicators were both low.
When high genetic risk was combined with loneliness, the difference reached approximately 1.85 years.
The scientists also found that the association between loneliness and accelerated biological aging was more pronounced among men, people under 60 years of age, participants with low incomes and those with sleep disorders.
Additional analysis using genetic data revealed a statistical association between a predisposition to loneliness and higher biological age. At the same time, regular attendance at sports clubs and participation in religious communities were associated with more favorable aging indicators.
However, these results do not prove that social activity in itself can slow down or reverse biological aging.
What the study findings mean for society
The authors believe that social connections should be regarded as one of the factors associated with healthy aging in the population.
Of particular importance is not only the opportunity to communicate regularly with other people, but also the availability of emotional support, trusting relationships and participation in community life.
At the same time, the researchers acknowledge the limitations of their work. The participants' biological age was measured only once, so the scientists could not track how changes in social circumstances affect the rate of aging in a particular individual.
Moreover, the results do not allow a definitive causal relationship to be established. It is possible that deteriorating health itself limits social activity and intensifies feelings of loneliness.
Most study participants lived in the United Kingdom and were of European ancestry, so the findings require additional verification in other countries and cultural settings.
To definitively confirm the potential influence of social contacts on biological aging, long-term studies with repeated measurements of biological indicators, as well as experiments aimed at reducing social isolation, are needed.
Nevertheless, the findings show that social well-being and the presence of supportive human relationships deserve attention alongside physical activity, nutrition and other factors associated with health and life expectancy.
The study was conducted by Rui Mao, Jiao Yuan, Tongtong Zhang, Fan Wang, Yun Zhong, Haonan Yuan, Fan Yang and Xin Meng. The research was published in Health Psychology, a journal published by the American Psychological Association.
