Global prevalence of social isolation among community-dwelling older adults: A systematic review and meta-analysis

•One in four community-dwelling older adults reported social isolation.•The sample size was found to be a significant covariate of the prevalence estimate in the subgroup analysis.•Well-designed observational research with standard measures is recommended. While the world's population ages, social isolation has continued to increase globally. However, no review exists on the prevalence of social isolation among community-dwelling older adults, and the global prevalence remains uncertain. This study aims to estimate the global prevalence of social isolation among community-dwelling older adults and to identify potential covariates including study characteristics (methodological diversity) or populations (clinical diversity) that contribute to the heterogeneity. This review searched through seven search engines and databases. The meta-analysis was conducted using the metafor package in the R software. The random-effects model was used to calculate the prevalence rates. Cochran's Q statistics and I2 statistics were used to assess the statistical heterogeneity of prevalence estimates. Studies were appraised using the Newcastle-Ottawa Scale and the Grading of Recommendations, Assessment, Development, and Evaluations criteria for the quality of individual articles and the certainty of the evidence, respectively. A total of 41 studies were selected from databases and reference lists. The pooled prevalence rate was 25% (95% CI: 21.0-30.0). The sample size was found to be a significant covariate of the prevalence estimate in the subgroup analysis. We found 13 high-quality studies, but the overall quality of evidence very low. This study provides the prevalence of social isolation in community-dwelling older adults, identifying vulnerable groups for targeted intervention. Well-designed observational research with standard measures is recommended for future studies.