Study design:
This is a retrospective cohort study from the Nationwide Readmission Database (NRD), a part of the Healthcare Cost and Utilization Project (HCUP) maintained by the Agency for Healthcare Research and Quality. NRD contains de-identified patient level public discharge data from 22 states, with an average of 14 million discharges per year, accounting for 56.6% of US hospitalizations. The NRD data elements include hospital characteristics, patient demographics, chronic co-morbidities, procedures, primary and secondary discharge diagnoses, payment source, and total costs. Since the database contains de-identified data, this study was exempted from institutional review board approval.