Understanding Recurrent Admissions for People with Heart Failure in New Zealand

Abstract

Conventional time-to-first event analyses do not fully represent burden of a chronic disease such as heart failure (HF). Extending analyses to subsequent recurrent events is required for improved understanding of risk factors associated with repeated hospital admissions over the course of the disease. We examined occurrence and risk factors of all-cause hospital readmissions through 4 years of follow-up period for adults admitted to a NZ hospital for the first-time with HF in 2013 or 2014. Several extended Cox models were assessed that differed in how they dealt with intra-subject correlation, and in how they modelled the time between hospitalisations. Of 23,736 patients discharged alive from index hospitalisation, 88% had ≥1 readmission and/or died from CVD during 4 years of follow-up. A standard time-to-first-event Cox model would have ignored 74% of total events experienced. The hazard ratios of predictors in the time-to-first-event model differed from those in the recurrent events models, including shifts in the statistical significance of key variables (ethnicity, HF aetiology). For most variables, smaller hazard ratios and narrower confidence intervals were observed from the Cox models which account for an increase in risk of event with number of previous admissions. Recurrent events analysis should be considered to understand longer-term impact of progression of HF and the true burden of long-term conditions. We demonstrated that the type of recurrent events model may affect the estimated covariate effects and its interpretation.