In Denmark, acute hospital contacts account for 72% of all inpatient and 8% of all outpatient contacts. There are 21 hospitals with adult acute care units in Denmark, of which Bispebjerg and Frederiksberg Hospital (BFH), a metropolitan hospital in Copenhagen, the capital of Denmark, is among the largest. To better understand and improve outcomes of patients with acute hospital needs, we have established a research collaboration called Bispebjerg Acute Cohort (BAC) and a national registry-based database as one of the research initiatives. BFH is notably different from other hospitals in Denmark when considering catchment areas and inhabitants since it is the only hospital covering a solely metropolitan catchment area. In preparation for establishing a local, acute cohort with continuous inclusion and collection of extra information and samples, we realized that it has not yet been established how a metropolitan hospital differs from urban hospitals that also have nonurban catchment areas and from hospitals in smaller cities