Abstract
INTRODUCTION: Functional disability in older adults refers to difficulties in performing daily activities. It is usually evaluated based on an individual's ability to carry out basic activities of daily living and instrumental activities of daily living. Although existing studies provide valuable insights, comprehensive global data on functional disability in basic and instrumental activities of daily living among older adults remain limited. This study aims to review existing research worldwide to estimate the overall pooled prevalence of functional disability in these areas. METHODS: Systematic searches were conducted across EMBASE, Scopus, PubMed/MEDLINE, and Google Scholar from May 5 to July 11, 2024. Cross-sectional studies worldwide on functional disability in basic and instrumental activities of daily living among adults aged 60 and older, published in English up to July 11, 2024 were included. Studies were excluded if they did not report the outcomes of interest, were inaccessible, case reports, low quality, review articles, or published in languages other than English. Data extraction and cleaning were performed using Microsoft Excel, and STATA version 17 was used to compute the pooled effect size with 95% confidence intervals (CIs) for functional disability in both basic activities of daily living and instrumental activities of daily living among older adults. To derive these estimates, we used weighted averages, where each study's prevalence was weighted by the inverse of its variance. Study heterogeneity was assessed using the Cochrane I² statistic and its associated p-value. Subgroup analysis and meta-regression were conducted to identify sources of heterogeneity. Sensitivity analysis was used to evaluate the impact of individual studies on the overall results. Publication bias was assessed with Egger's test and funnel plots, and was addressed through trim-and-fill analysis. RESULTS: This review includes 35 studies with a total of 133,827 participants. The pooled prevalence of functional disability in basic activities of daily living was estimated at 26.07% (95% CI: 19.04-32.74), while on instrumental activities of daily living, it was estimated at 45.15% (95% CI: 36.02-54.29). After applying the trim-and-fill method, the adjusted overall prevalence of disability in basic activities of daily living was 15.12%, (a 95% CI: 11.25-19.13%). Subgroup analysis showed highest prevalence in Africa (BADL: 42.91%, IADL: 69.34%) and lowest in Asia (BADL: 19.15%, IADL: 32.66%). Participants aged 65 and above, those in institutional settings, and studies with smaller sample sizes tended to report higher levels of functional disability. CONCLUSIONS: Nearly one-fourth of the study participants had functional disability related to basic activities of daily living, while about half experienced disability in instrumental activities of daily living. This emphasizes the need for continued effort in improving the quality of life and support systems for individuals facing functional disability, particularly in instrumental activities.