gms | German Medical Science

Background: Studies evaluating interventions to address polypharmacy often fail to show impact on clinical endpoints because they are insufficiently targeted at those at highest risk and because they consider all-cause rather than drug-related hospital admissions. Therefore, the aim of this study is to examine the utility of a new approach to measuring adverse drug event-related hospital admissions in large electronic data bases using prespecified combinations of specific hospital admissions and preceding ambulatory medication.

Materials and Methods: We conducted a retrospective population-based cohort study in people aged ≥ 40 years in order to estimate and compare the incidence of emergency hospital admissions due to a) all-cause (AC-H), b) certain adverse events (AE-H) and c) certain adverse drug events (ADE-H) in two Scottish health boards (NHS Tayside and Fife) in 2019. In order to identify patient-level predictors for such admissions in the following year, we performed binomial multivariate logistic regression with a preceding lasso regression for variable selection among people with polypharmacy (i.e., simultaneous use of 5 or more drugs at cohort entry).

Results: Our preliminary results found that the overall incidence of AC-H, AE-H and ADE-H was 913.8, 251.4 and 91.6 per 10,000 residents, respectively. Falls and fall-related injuries were the most commonly documented reason for AE-H as well as ADE-H with a respective incidence of 102.8 and 31.8 per 10,000 residents. The predictors included in multivariate regression models explained 11.6% of variation in the risk of AE-H (R²=49,168.08) and 10.3% in the risk of ADE-H (R²=27,087.16) among people with polypharmacy. AE-H as well as ADE-H were most strongly associated with increased age (≥ 80 years vs. 40-64 years; multivariate OR: AE-H: 4.03; 95% CI 3.75 – 4.33; ADE-H: 3.72; 95% CI 3.35 – 4.14) and length of stay in hospital in previous year (> 30 days vs. 0 days; multivariate OR: AE-H: 3.27; 95% CI 2.49 – 4.28; ADE-H: 2.79; 95% CI 1.94 – 4.01).

Conclusion: Our finding of a much lower incidence of drug-related (ADE-H) vs. other cause (AC-H or AE-H) hospital admissions suggests that this novel approach may be a more specific method for evaluating the impact of quality improvement interventions targeting polypharmacy in primary care. Strategies to improve targeting of patients at high risk of drug-related outcomes may be improved by estimating risk of specific ADE-H (such as falls and fall-related injuries or gastrointestinal bleeding) rather than any ADE-H.