Polypharmacy, comorbidity and frailty: a complex interplay in older patients at the emergency department

PURPOSE: Older adults at the emergency department (ED) with polypharmacy, comorbidity, and frailty are at risk of adverse health outcomes. We investigated the association of polypharmacy with adverse health outcomes, in relation to comorbidity and frailty. METHODS: This is a prospective cohort study in ED patients ≥ 70 years. Non-polypharmacy was defined as 0–4 medications, polypharmacy 5–9 and excessive polypharmacy ≥ 10. Comorbidity was classified by the Charlson comorbidity index (CCI). Frailty was defined by the Identification of Seniors At Risk—Hospitalized Patients (ISAR-HP) score. The primary outcome was 3-month mortality. Secondary outcomes were readmission to an ED/hospital ward and a self-reported fall < 3 months. The association between polypharmacy, comorbidity and frailty was analyzed by logistic regression. RESULTS: 881 patients were included. 43% had polypharmacy and 18% had excessive polypharmacy. After 3 months, 9% died, 30% were readmitted, and 21% reported a fall. Compared with non-polypharmacy, the odds ratio (OR) for mortality ranged from 2.62 (95% CI 1.39–4.93) in patients with polypharmacy to 3.92 (95% CI 1.95–7.90) in excessive polypharmacy. The OR weakened after adjustment for comorbidity: 1.80 (95% CI 0.92–3.52) and 2.32 (95% CI 1.10–4.90). After adjusting for frailty, the OR weakened to 2.10 (95% CI 1.10–4.00) and OR 2.40 (95% CI 1.15–5.02). No significant association was found for readmission or self-reported fall. CONCLUSIONS: Polypharmacy is common in older patients at the ED. Polypharmacy, and especially excessive polypharmacy, is associated with an increased risk of mortality. The observed association is complex given the confounding effect of comorbidity and frailty. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s41999-022-00664-y.