Oral Presentation Australian and New Zealand Society for Geriatric Medicine Annual Scientific Meeting 2025

Retrospective Multi-centre Cohort Study of Polypharmacy and its Association with Outcomes in Older Surgical Inpatients (119652)

Bonnie M Liu 1 2 , Kenji Fujita 1 , Danijela Gnjidic 3 , Janani Thillainadesan 4 , Sarah N Hilmer 1
  1. Ageing and Pharmacology Laboratory, Kolling Institute, Faculty of Medicine and Health, The University of Sydney and the Northern Sydney Local Health District, Sydney, NSW, Australia
  2. Aged Care Department, Royal North Shore Hospital, Sydney, NSW, Australia
  3. Sydney Pharmacy School, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW , Australia
  4. Department of Geriatric Medicine and Centre for Education and Research on Ageing, Concord Hospital, Sydney, NSW, Australia

Aims: To investigate the associations of the number of medications and exposure to the Drug Burden Index (DBI) with clinical outcomes in older surgical inpatients.

Methods: A multi-centre retrospective cohort study using de-identified data was conducted. Participants were ≥65 years admitted under surgical teams at five Australian hospitals for ≥48 hours between 4/1/22-3/1/23. Number of regular medications was counted on admission and discharge. Exposure to the DBI throughout admission was calculated using area under the curve for DBI/days of admission (AUC DBI/days). Analysis of binary outcomes (falls, adverse drug events, delirium, pressure areas, post-operative surgical complications) used multivariate logistic regression and continuous outcomes (frailty and length of stay (LOS)) applied multivariate gamma regression.

Results: Median age of 13815 participants was 77 years and 51.0% were male. Median (IQR) number of medications on admission was 5 (2-9) and on discharge was 9 (6-13). Median AUC DBI/days was 0.13 (0-0.5).  Number of admission medications was associated with delirium (Odds Ratio (OR) 1.02, 95%CI: 1.00-1.03), adverse drug events (OR 1.02, 95%CI:1.01-1.04), pressure areas (OR 1.58, 95%CI:1.36-1.84), frailty (RR 1.01, 95%CI:1.00-1.01) and increased LOS (RR 1.01, 95%CI: 1.01-1.02).  AUC DBI/days was associated with falls (OR 1.38, 95%CI:1.28-1.49), delirium (OR 1.72, 95%CI:1.54-1.91), adverse drug events (OR 1.18, 95%CI:1.04-1.34), pressure areas (OR 1.58, 95%CI:1.36-1.84), frailty (Rate Ratio (RR) 1.30, 95%CI:1.26-1.35) and increased LOS (RR 1.44, 95%CI:1.38-1.50).

Conclusion: This is the first study to analyse the association between the DBI and outcomes in a surgical population and found polypharmacy and high-risk medications were associated with adverse outcomes.