Social isolation as a risk factor for all-cause mortality: Systematic review and meta-analysis of cohort studies

BACKGROUND: Although several epidemiological studies have linked social isolation to increased risk of mortality, the magnitude of any effect is unclear, in part because of the use of different measures of social isolation. OBJECTIVE: To examine the association between social isolation and all-cause mortality and investigate whether it differs in various subgroups or populations. DATA SOURCES: We searched for relevant studies in electronic databases: MEDLINE (1946 to December 31, 2021), EMBASE (1974 to December 31, 2021), and PsycINFO (1806 to December 31, 2021). SELECTION CRITERIA: We included both prospective and retrospective cohort studies that examined the association between social isolation and all-cause mortality among adults. DATA COLLECTION AND ANALYSIS: Two reviewers screened and extracted data independently. We contacted study authors to obtain missing information whenever possible. Data were pooled using a random effect model to calculate estimates of the effects of social isolation on all-cause mortality. RESULTS: Data from studies involving 1.30 million individuals were included. The pooled hazard ratio of social isolation for all-cause mortality was 1.33 (95% confidence interval; 1.26–1.41, heterogeneity: Chi² = 112.51, P < 0.00001, I² = 76%). CONCLUSION: Social isolation is associated with increased risk for all-cause mortality. REGISTRATION: PROSPERO (CRD42020152351).