Loneliness and social isolation were associated with fewer years of life free of major chronic diseases, with stronger associations for mental disorders than physical diseases.
Researchers conducted a prospective cohort study using UK Biobank data from 277,489 participants, including 134,318 women and 143,171 men, who were free of the 7 major chronic diseases examined at baseline. Participants were recruited across England, Scotland, and Wales from 2006 to 2010. Loneliness and social isolation were assessed at baseline using self-reported 2-item and 3-item scales, respectively. Participants were classified as experiencing neither loneliness nor social isolation, loneliness only, social isolation only, or both.
The primary outcome was life expectancy free of 7 major chronic diseases: type 2 diabetes, cardiovascular disease, chronic respiratory disease, neurodegenerative disease, cancer, depression, and anxiety. Researchers also estimated life expectancy free of the 5 physical diseases and 2 mental disorders separately. Multistate life tables were used to estimate disease-free life expectancy, and secondary analyses examined whether a healthy lifestyle—based on smoking, body mass index, physical activity, diet, and sleep—modified the loss of disease-free life expectancy associated with loneliness and social isolation.
During a median follow-up of approximately 14 years for mortality and 13 years for chronic disease, 16,356 deaths and 78,829 incident chronic disease events occurred. At age 50 years, women experiencing neither loneliness nor social isolation had an estimated 25.5 years free of the 7 diseases, compared with 23.3 years among those with loneliness only, 24.2 years among those with social isolation only, and 22.6 years among those with both. The corresponding estimates among men were 21.8, 20.5, 20.8, and 19.6 years.
The differences were greater for mental disorder–free life expectancy than physical disease–free life expectancy. At age 50 years, women experiencing both loneliness and social isolation had 3.7 fewer years free of depression and anxiety than women experiencing neither, whereas men experiencing both had 5.8 fewer years. For the 5 physical diseases, women and men experiencing both had 2.4 and 1.7 fewer disease-free years, respectively.
When the exposures were considered separately, women with loneliness had 3.9 fewer years free of depression and anxiety, compared with 2.0 fewer years among women with social isolation. Among men, loneliness and social isolation were associated with 2.9 and 3.0 fewer mental disorder–free years, respectively. For physical disease–free life expectancy, loneliness was associated with losses of 1.5 years among women and 1.0 year among men, whereas social isolation was associated with losses of 1.4 and 0.9 years, respectively. The associations generally narrowed with increasing age, and sensitivity analyses excluding participants who developed a chronic disease or died within the first 2 years did not appreciably change the findings.
Lifestyle analyses suggested different patterns for social isolation and loneliness. Although a healthier lifestyle was associated with longer disease-free life expectancy regardless of loneliness status, the loss associated with loneliness did not significantly narrow across increasingly healthy lifestyle categories. In contrast, the loss of disease-free life expectancy associated with social isolation narrowed as lifestyle scores increased.
Among women with an unhealthy lifestyle, social isolation was associated with 2.2 fewer years free of depression and anxiety. The difference narrowed to 1.1 years among those with an intermediate lifestyle and 0.6 years among those with a healthy lifestyle; the latter difference was not statistically significant. Among men, however, social isolation remained associated with fewer mental disorder–free years even in the healthy lifestyle group.
Loneliness and social isolation were measured using brief self-reported scales only at baseline, preventing assessment of changes over time and potentially introducing misclassification. Lifestyle factors were also self-reported, and categorizing lifestyle scores into 3 groups may have obscured more nuanced associations. The multistate life-table analysis incorporated a Markov assumption that was not formally tested. Because the study was observational, causal relationships could not be established. The UK Biobank had a 5.5% response rate and is not representative of the broader UK population, potentially limiting generalizability.
Overall, the findings linked both loneliness and social isolation to fewer years free of major chronic diseases, particularly depression and anxiety, while suggesting that a healthier lifestyle may be associated with a smaller loss of disease-free life expectancy related to social isolation but not loneliness.
The authors reported no competing interests.
Source: Nature Communications
