Background: The reported prevalence of depressive symptoms (depression hereafter) among older adults varied widely across different studies. This was a meta-analysis to systematically examine the global prevalence of depression among older populations and its associated factors.

Methods: A systematic literature search was performed in PubMed, EMBASE, PsycINFO, and Web of Science. Due to the differences in demographic and clinical characteristics between studies, random-effects model was used to calculate the pooled prevalence of depression and its 95% confidence interval (95% CI).

Results: In total, 55 studies with 59,851 individuals met the study criteria and were included in the analyses. The overall prevalence of depression was 35.1% (95%CI: 30.2-40.4%). Subgroup analyses revealed that different sampling methods (Q=10592.49, p = 0.037), Geriatric Depression Scale versions (Q=13712.55, p < 0.001) and income levels (Q=14.028, P < 0.001) were significantly associated with the pooled prevalence of depression in older adults. In the meta-regression analyses, time of survey (B=0.012, z = 2.30, p = 0.029) was positively associated, and mean age (B=-0.018, z = 2.10, p = 0.044) was negatively associated with the prevalence of depression in older populations. The funnel plot and Egger's test did not reveal any significant publication bias (Egger's test: t = 1.93, p = 0.059).

Conclusion: This meta-analysis found that over a third of older populations globally had depression. Effective preventive measures, regular screening and timely interventions are needed to address this highly prevalent public health problem among older adults.