Prevalence and risk factors for adverse drug reactions in older adults in the acute care setting

Tariq M. Alhawassi, Ines Krass, Lisa G. Pont

Research output: Contribution to journalMeeting abstract


Background: Adverse drug reactions (ADRs) are common drug-related problems associated with increased morbidity, mortality and total healthcare costs in the general population, yet less is known about ADRs in older populations.
Objectives: The aims of this study were to estimate the prevalence of ADRs and identify factors associated with an increased ADR risk in an older population.
Methods: A retrospective cross-sectional survey of medical records at a large teaching hospital in metropolitan Sydney, Australia, was conducted. A systematic sample of all patients aged ≥65 years who were admitted between 1 January 2010 and 31 December 2010 was included. ADRs, defined according to the WHO definition, were identified by a trained clinical pharmacist. Causality was determined according to the Naranjo criteria and severity, preventability and contribution to hospitalisation by the Hallas criteria. Factors associated with an increased ADR risk were identified using multifactorial logistic regression.
Results: The study cohort comprised 503 patients (mean age (±SD)=80.3±8.2). Approximately one quarter of the cohort (26.2%) experienced an ADR. The majority of ADRs were classified as definite (4.5%) or probable (76.5%) and were considered the ‘dominant’ or ‘partial’ reason for admission in 20.5% and 12.1% of admissions, respectively. Approximately one-third (31.8%) of ADRs were considered severe and 47.6% moderate. Most were considered either definitely (15.2%) or possibly (50.0%) avoidable. Female gender (OR=0.5, 95%CI [0.30, 0.80]), increased number of medications prior to admission (OR=1.1, [1.03, 1.16]), previous allergy or ADR (OR=4.9, [2.87, 8.40]), impaired renal function (OR=0.9, [0.97, 0.99]) and current or past diagnosis of atrial fibrillation (OR=2.0, [1.17, 3.28]) were all associated with an increased ADR risk.
Conclusions: ADRs are a considerable health problem for older persons. One quarter of all older persons admitted to hospital experienced an ADR, with threefourth of these leading to serious outcomes. Of greater importance, 65% of all ADRs experienced by older persons were considered avoidable. Strategies to improve detection of ADRs and a greater awareness of those older persons at increased risk of an ADR are needed.
Original languageEnglish
Article number158
Pages (from-to)91
Number of pages1
JournalPharmacoepidemiology and Drug Safety
Issue numberSuppl. 1
Publication statusPublished - Sep 2015
Externally publishedYes
EventInternational Conference on Pharmacoepidemiology and Therapeutic Risk Management (31st : 2015) - Boston, United States
Duration: 22 Aug 201526 Aug 2015

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