Rehospitalization for pneumonia after first pneumonia admission: Incidence and predictors in a population-based cohort study

Abstract

Background and objectives: Hospital readmissions are a frequent complication of pneumonia. Most data regarding readmissions are obtained from the United States, whereas few data are available from the European healthcare utilization (HCU) systems. In a large cohort of Italian patients with a previous hospitalization for pneumonia, our aim was to evaluate the incidence and predictors of early readmissions due to pneumonia.

Methods: This is a observational retrospective, population based, cohort study. Data were retrieved from the HCU databases of the Italian Lombardy region. 203,768 patients were hospitalized for pneumonia between 2003 and 2012. The outcome was the first rehospitalization for pneumonia. The patients were followed up after the index hospital admission to estimate the hazard ratio, and relative 95% confidence interval, of the outcome associated with the risk factors that we had identified.

Results: 7,275 patients (3.6%) had an early pneumonia readmission. Male gender, age ≥70 years, length of stay of the first admission and a higher burden of comorbidities were significantly associated with the outcome. Chronic use of antidepressants, antiarrhythmics, glucocorticoids and drugs for obstructive airway diseases were also more frequently prescribed in patients requiring rehospitalization. Previous use of inhaled broncodilators, including both beta2-agonists and anticholinergics, but not inhaled steroids, were associated with an increased risk of hospital readmission.

Conclusions: Frail elderly patients with multiple comorbidities and complex drug regimens were at higher risk of early rehospitalization and, thus, may require closer follow-up and prevention strategies.

Fig 1. Flow-chart of inclusion and exclusion criteria for the study cohort selection.

Lombardy region, Italy, 2003–2012. NHS, national health system.

Fig 2. Age-stratified Hazard ratios (HR), and relative 95% confidence intervals (CI), of early rehospitalizations for pneumonia associated with selected risk factors, estimated with a multivariable Cox proportional hazard model.

Lombardy region, Italy, 2003–2012. Estimates, stratified for age classes (<70 and ≥70 years), were obtained through a multivariable Cox proportional hazard model. For each covariate of which HR of the outcome was reported in the figure, the reference category was that of unexposed patients to this covariate (e.g., for persistent aspirin therapy the reference category was that of patients who was not exposed to a persistent aspirin therapy). NSAIDs, nonsteroidal anti-inflammatory drugs.

Fig 3. Influence of smoking status as an unmeasured confounder on the association between respiratory failure (or mechanical ventilation use) during the index hospital stay and the risk of experiencing a pneumonia readmission.

Lombardy region, Italy, 2003–2012. The graph indicates the combinations of confounder-outcome and exposure-confounder associations that would be required to move the observed effect of the considered risk factors towards the null. We set the possible generic unmeasured confounder, e.g., smoking status: (i) to have a 21% prevalence of exposure among patients hospitalized for pneumonia [17], (ii) to increase the risk of the outcome onset up to 10-fold more in patients exposed to the confounder than in those not exposed, and (iii) to be up to 10-fold more common among patients exposed to the predisposing factor than in those not exposed.