Too many, too few, or too unsafe? Impact of inappropriate prescribing on mortality, and hospitalisation in a cohort of community-dwelling oldest old.

AIMS: Little is known about the impact of inappropriate prescribing (IP) in community-dwelling adults, aged 80 years and older. The prevalence at baseline (November 2008September 2009) and impact of IP (misuse and underuse) after 18 months on mortality and hospitalization in a cohort of community-dwelling adults, aged 80 years and older (n = 503) was studied. METHODS: Screening Tool of Older People's Prescriptions (STOPP-2, misuse) and Screening Tool to Alert to Right Treatment (START-2, underuse) criteria were cross-referenced and linked to the medication use (in Anatomical Therapeutic Chemical coding) and clinical problems. Survival analysis until death or first hospitalization was performed at 18 months after inclusion using Kaplan-Meier, with Cox regression to control for covariates. RESULTS: Mean age was 84.4 (range 80-102) years. Mean number of medications prescribed was 5 (range 0-16). Polypharmacy (≥5 medications, 58%), underuse (67%) and misuse (56%) were high. Underuse and misuse coexisted in 40% and were absent in 17% of the population. A higher number of prescribed medications was correlated with more misused medications (rs = .51, P < 0.001) and underused medications (rs = .26, P < 0.001). Mortality and hospitalization rate were 8.9%, and 31.0%, respectively. After adjustment for number of medications and misused medications, there was an increased risk of mortality (HR 1.39, 95% CI 1.10, 1.76) and hospitalization (HR 1.26, 95% CI 1.10, 1.45) for every additional underused medication. Associations with misuse were less clear. CONCLUSION: IP (polypharmacy, underuse and misuse) was highly prevalent in adults, aged 80 years and older. Surprisingly, underuse and not misuse had strong associations with mortality and hospitalization.