Global incidence and prevalence of delirium and its risk factors in medically hospitalized older patients: A systematic review and meta-analysis

Background: Delirium is a common complication among older medical patients that can lead to undesirable outcomes. Objectives: This study systematically investigated the incidence, prevalence, and risk factors of delirium to improve its recognition, prevention, and management in medically hospitalized older patients. Methods: The study protocol was registered at PROSPERO on April 29, 2024 (registration number: CRD42024536624). We searched the PubMed, Embase, and ProQuest databases for relevant articles published between database inception and September 25, 2024. We included observational studies reporting the prevalence, incidence, and risk factors of delirium among medically hospitalized older patients. Two independent reviewers extracted the data. A random-effects model was used for data analysis. Results: A total of 35 studies encompassing 12,097 participants met the inclusion criteria, yielding a 23.6 % pooled prevalence of delirium (95 % confidence interval = 19 % to 29 %) and a 13.5 % pooled incidence of delirium (n = 32, 95 % confidence interval = 11 % to 17 %) among medically hospitalized older patients. Study quality and country were significant moderators for explaining the heterogeneity observed in the prevalence and incidence of delirium, respectively (both P < 0.001). The risk factors of delirium included frailty (odds ratio = 2.05), physical restraints (5.01), prior falls (1.99), severe illness (1.32) (evaluated using the Acute Physiology and Chronic Health Evaluation II), and cognitive impairment (2.61). Older age increased delirium risk, whereas years of education mitigated it (B = 1.69 and 0.92, respectively). Conclusion: Our findings considerably enhance the understanding of the prevalence of delirium and its influencing factors in medically hospitalized older patients. The insights this study provides can enable health-care providers to apply quick and effective assessment tools and can thereby support the implementation of interventions to prevent delirium. Registration: The study protocol has been prospectively registered on PROSPERO (registration no. CRD42024536624).