Importance: Individuals with obesity experience markedly higher levels of social isolation and loneliness than those without obesity, but little is known about whether improvement of social isolation or loneliness might attenuate obesity-related excess risk of mortality.
Objective: To investigate whether improvement of social isolation or loneliness is associated with lower obesity-related excess risk of mortality.
Design, setting, and participants: This cohort study included individuals without cancer or cardiovascular disease (CVD) at baseline from the UK Biobank with follow-up beginning in March 2006 and ending in November 2021.
Main outcomes and measures: All-cause, cancer-related, and CVD-related mortality were estimated.
Results: A total of 398 972 participants were included in this study (mean [SD] age, 55.85 [8.08] years; 220 469 [55.26%] women; 13 734 [3.44%] Asian, 14 179 [3.55%] multiracial, and 363 685 [91.16%] White participants). Overall, 93 357 (23.40%) had obesity, and 305 615 (76.60%) did not. During a median (IQR) follow-up of 12.73 (12.01-13.43) years, a total of 22 872 incident deaths were recorded. Compared with participants with obesity with an index of 2 or greater for social isolation, the multivariable adjusted hazard ratios (HRs) for all-cause mortality were 0.85 (95% CI, 0.79-0.91) and 0.74 (95% CI, 0.69-0.80) for participants with obesity and a social isolation index of 1 and 0, respectively (P for trend < .001); compared with participants with obesity and an index of 2 for loneliness, the HRs and 0.97 (95% CI, 0.89-1.06) and 0.86 (95% CI, 0.79-0.94) for participants with obesity and a loneliness index of 1 and 0, respectively (P for trend < .001). As the index of social isolation and loneliness went from highest to lowest, the HR for all-cause mortality decreased by 36% and 9%, respectively, in people with obesity compared with people without obesity using the multivariable model. Social isolation was ranked higher than loneliness, depression, anxiety, and lifestyle-related risk factors including alcohol, physical activity, and healthy diet for estimating the risks of all-cause mortality, cancer-related mortality, and CVD-related mortality.
Conclusions and relevance: In this cohort study of UK Biobank participants, a lower index of social isolation or loneliness was associated with a decreased risk of all-cause mortality among people with obesity, and improvement of social isolation and loneliness attenuated obesity-related excess risk of all-cause mortality.