The association of inappropriate drug use with hospitalisation and mortality: a population-based study of the very old.

BACKGROUND AND OBJECTIVE: Inappropriate prescribing is an important and possibly preventable risk factor for adverse drug reactions (ADRs) in the elderly, and hospital-based studies have shown that a large proportion of admissions is a result of ADRs. However, little is known about how inappropriate drug use (IDU) affects the elderly at the population level. The aim of this study was to explore possible associations of IDU with acute hospitalisation and mortality in an elderly population during 3 years of follow-up.

PATIENTS AND METHODS: Data from a rural, population-based, longitudinal cohort study within the Kungsholmen Project, Sweden, were used. 785 participants, > or=75 years of age, had complete data on drug use and selected covariates collected during baseline investigation from 1995 to 1998, and were included in the study. Hospitalisation and mortality data during 3 years after inclusion were collected. IDU was assessed at baseline using consensus-based criteria applicable to available data (derived from Beers' criteria, Canadian criteria and clinical indicators of drug-related morbidity in older adults) with the addition of potentially dangerous drug duplication and additional potentially hazardous drug-drug interactions. IDU was defined as presence of at least one inappropriate drug regimen according to the study criteria. Logistic regression and proportional hazard models were used, respectively, to study the association of IDU with hospitalisation and mortality.

RESULTS: Drugs were used on a regular or 'as needed' basis by 91.6% of the study population, with a mean of 4.4 drugs per person. IDU was common, with a prevalence of 18.6% and was associated with increased risk of at least one acute hospitalisation in community-living elderly, after adjustment for age, sex, education, comorbidity, dependency in activities of daily living (ADL) and smoking. The odds ratio was 2.72 (95% CI 1.64, 4.51). No association with mortality was found, after adjustment for age, sex, housing, education, comorbidity, ADL-dependency, smoking and body mass index.

CONCLUSION: Polypharmacy and IDU are common among the elderly and IDU is associated with acute hospitalisation in community-living elderly. Although causality cannot be established with this study design, the results are consistent with the high prevalence of drug-related hospital admissions found in hospital-based studies. Our results indicate that it is desirable with current knowledge, to reduce IDU through information to physicians and careful prescribing.