Data source
We obtained data from the Nationwide Inpatient Sample (NIS) Database from 2010 to 2017. The Agency for Healthcare Research and Quality sponsors the NIS as part of the Healthcare Cost and Utilization Project. The NIS is the largest publicly available all-payer inpatient healthcare database designed to produce national estimates of inpatient utilization, access, cost, quality, and outcomes. Unweighted, it contains data from more than 7 million hospital stays each year. Weighted, it estimates more than 35 million hospitalizations nationally. The data include diagnosis and procedure codes from the International Classification of Diseases, Ninth and Tenth Revision, Clinical Modification (ICD-9-CM and ICD-10-CM), and Clinical Classifications Software diagnosis and procedure classifications. The Institutional Review Board at the University of Pittsburgh evaluated this study and deemed it not to qualify as human subject research. The research team completed relevant HCUP training modules and signed the NIS Data Use Agreement.