Hospital admissions due to adverse drug reactions and adverse drug events in older adults: A systematic review

Abstract Background Adverse drug events (ADEs) and adverse drug reactions (ADRs) are consistently reported to be the cause of up to 30% of hospital admissions in older adults resulting in significant morbidity and mortality with an added health economic burden. We wish to systematically review the literature to establish the frequency of ADRs and ADEs as a cause of hospitalization with a secondary aim of determining the implicated drugs and risk factors. Methods Standard databases and citations were searched (2015 to 2024) and studies specifically assessing ADR and ADE prevalence and risk factors in older adults were included. The systematic review was registered in PROSPERO (CRD42024613426). The Joanna Briggs Institute (JBI) criteria was used to assess quality, and the risk of bias was determined using the ‘risk of bias in non-randomised studies – of exposure’ (ROBINS-E). A narrative synthesis approach was used to present the findings. Results Eight studies met the inclusion criteria and underwent further evaluation and quality assessment. The prevalence of ADRs was reported to be 3.3% to 23.1% and the reported prevalence of ADEs ranged from 11.75% to 18%. The median age of those included ranged from 77 to 86 years. Falls (19.4-20.9%), hypotension (7.6-33.5%), delirium (7.3-12.9%) and bleeding (8-30.2%) were the most encountered ADR/ADEs with anti-thrombotics (11.5-30.2%) diuretics (14.7-30.2%) and renin-angiotensin-aldosterone system (RAAS) inhibitors (7.5-8.9%) accounting for the highest proportion of ADR/ADE causative agents. Only two studies performed logistic regression analysis to establish risk factors for ADE/ADRs. Conclusion This review has limitations stemming from the heterogeneity in the included studies and the exclusion of grey literature. However, ADRs and ADEs remain a significant cause of hospital admissions in older adults despite their reported preventability. Future research into methods for risk assessment and prevention of ADEs and ADRs is urgently needed to address this significant health burden for older adults.