Aims: Comprehensively investigate prescribing in usual care of hospitalized older people with respect to polypharmacy; potentially inappropriate medications (PIMs) according to Beers criteria; and cumulative anticholinergic and sedative medication exposure calculated with Drug Burden Index (DBI). Specifically, to quantify exposure to these measures on admission, changes between admission and discharge, associations with adverse outcomes and medication costs.

Methods: Established new retrospective inpatient cohort of 2000 adults aged ≥75 years, consecutively admitted to 6 hospitals in Sydney, Australia, with detailed information on medications, clinical characteristics and outcomes. Conducted cross-sectional analyses of index admission data from cohort.

Results: Cohort had mean (standard deviation) age 86.0 (5.8) years, 59% female, 21% from residential aged care. On admission, prevalence of polypharmacy was 77%, PIMs 34% and DBI > 0 in 53%. From admission to discharge, mean difference (95% confidence interval) in total number of medications increased 1.05 (0.92, 1.18); while prevalence of exposure to PIMs (-3.8% [-5.4, -2.1]) and mean DBI score (-0.02 [-0.04, -0.01]) decreased. PIMs and DBI score were associated with increased risks (adjusted odds ratio [95% confidence interval]) of falls (PIMs 1.63 [1.28, 2.08]; DBI score 1.21[1.00, 1.46]) and delirium (PIMs 1.76 [1.38, 1.46]; DBI score 1.42 [1.19, 1.71]). Each measure was associated with increased risk of adverse drug reactions (polypharmacy 1.42 [1.19, 1.71]; PIMs 1.87 [1.40, 2.49]; DBI score 1.90 [1.55, 2.15]). Cost (AU$/patient/hospital day) of medications contributing to PIMs and DBI was low ($0.29 and $0.88).

Conclusion: In this large cohort of older inpatients, usual hospital care results in an increase in number of medications and small reductions in PIMs and DBI, with variable associations with adverse outcomes.