Epidemiology and characteristics of repeat adverse drug reactions and associated clinical outcomes in older adults: a systematic review and meta-analysis

PURPOSE: To systematically review and synthesise evidence on the incidence, characteristics, risk factors, and clinical outcomes of repeat adverse drug reactions (ADRs) in older adults. METHODS: A comprehensive search of four major databases was conducted. Studies reporting data on both index (initial) and repeat ADRs in populations with a mean or median age ≥ 60 years were included. A repeat ADR was defined as the occurrence of the same or a different ADR following an index ADR in the same individual. A meta-analysis estimated the pooled incidence rate (IR) of at least one repeat ADR-related hospitalisation. The protocol was registered in PROSPERO (CRD420251086319). RESULTS: = 82.7%). Three studies found that the same drugs or drug classes were implicated in both index and repeat ADR-related hospitalisations in 41.7 to 60% of cases. In-hospital mortality among patients with repeat ADR-related hospitalisations ranged from 0 to 68.1% (3 studies). CONCLUSION: Repeat ADRs and related hospitalisations pose a non-trivial risk in older adults and often involve the same drugs. Future research should evaluate system-level strategies to reduce preventable repeat events.