Social isolation and loneliness and mortality among cancer survivors: a prospective cohort study.

Background: Social isolation and loneliness are associated with mortality, but their impact on cause-specific mortality in cancer survivors remains unclear. Methods: This cohort study enrolled UK Biobank participants with cancer at baseline, followed up from March 2006 to September 2024. Social isolation and loneliness were assessed by self-reported questionnaires. Outcomes included all-cause, cancer-specific, and cardiovascular disease (CVD)-related mortality. Associations were evaluated using Cox proportional hazards models. Results: A total of 32,524 participants were included in this study (60.2% women; mean age, 60.3 years). During a median 15.7-year follow-up, 5,945 deaths occurred. Social isolation was significantly associated with increased all-cause (HR, 1.22; 95%CI, 1.12-1.32), cancer-specific (HR, 1.16; 95%CI, 1.04-1.28), and CVD-related (HR, 1.32; 95%CI, 1.07-1.63) mortality. Loneliness was not associated with all-cause mortality (HR, 0.98; 95%CI, 0.93-1.04), but independently associated with increased CVD-related mortality (HR, 1.26; 95%CI, 1.08-1.47). Exploratory analyses identified distinct prognostic impacts of specific isolation measures: living alone was linked to higher all-cause and non-cancer mortality across most cancer types, while weekly social activities and monthly family/friends visits were protective. Conclusions: Social isolation was associated with increased risks of all-cause, cancer-specific, and CVD-related mortality. Loneliness was associated with elevated CVD-related mortality.