Hospitalization rates during potentially inappropriate medication use in a large population-based cohort of older...

The temporal relationship between potentially inappropriate medication (PIM) use and hospitalization remains uncertain. We examined whether current PIM use increases the rate of hospitalization and estimated the rate of hospitalization during exposure to individual PIMs.

A retrospective population-based cohort study of 1 480 137 older adults was conducted using the 2003-2013 Italian Emilia-Romagna Regional administrative healthcare database (~4.5 million residents), which includes demographic, hospital and outpatient prescription information. Each day of follow-up was defined as exposed/unexposed to PIMs that 'should always be avoided', according to the Maio criteria, an Italian modified version of the Beers criteria. The study outcome was all-cause hospitalizations. Crude PIM-related hospitalization rates were calculated for individual PIMs. Repeated-events Cox proportional hazards models with time-dependent covariates estimated adjusted hazard ratios for hospitalization during PIM exposure, as defined by three versions of the Maio criteria (v2007, v2011, v2014).

During >10 million person-years of follow-up, 54.2% of individuals used ≥1 PIM and 10.9% of all person-time was exposed to v2014 PIMs. Among 1 604 901 hospitalizations, 15.6% occurred during v2014 PIM exposure. Crude hospitalization rates during v2014 PIM-exposed and unexposed person-time were 228.1 and 152.1 per 1000 person-years, respectively. The PIM with the highest rate of hospitalization was ketorolac, while nonsteroidal anti-inflammatory drugs had the most exposure time. The hazard of hospitalization was 16% greater (hazard ratio = 1.16; 95% confidence interval 1.14, 1.18) among patients exposed to v2014 PIMs. The v2007 and v2011 estimates were similar.

In this large population-based cohort of older adults, we found a 16% increased hospitalization risk associated with PIM exposure.