Data Sources

Every Danish citizen is provided with a unique identifier, making it possible to cross‐link different national administrative registries. We used the Danish National Patient Registry, The Prescription Registry, The Danish Population Registry, and the Danish Microbiology Database. The Danish National Patient Registry holds information on every hospital admission in Denmark since 1977. The registry is based on the discharge papers from hospitals in Denmark coded by physicians. The International Classification of Diseases, Eighth Revision (ICD‐8), was used up until 1994; and since then, the International Classification of Diseases, Tenth Revision (ICD‐10), has been used. We used the National Patient Registry to identify the study population and comorbidity that was assessed as a primary or secondary diagnosis code before index date (for codes used, please see Table S1). The National Patient Registry also holds information on surgical procedures, and heart valve surgery during IE admission was assessed (Table S1). The Prescription Registry holds information on every filled prescription from a Danish pharmacy since 1994, with data of drug type and date of collection. The Anatomical Therapeutic Chemical Classification System is used to classify drug types. Concomitant pharmacotherapy was used to assess conditions requiring medication, defined as a filled prescription 6 months before index date. The Population Registry holds information on migration status, sex, date of birth, and date of death. The Danish registries are validated, complete, and described in detail previously. ^{13 , 14 , 15}