Table 1.

Description of registers included in the study

Name of register	Description
Care Home Data (Plejehjemsdata)	The register was introduced in 2020 and can identify all Danish citizens registered with a care home address by combining information from the Civil Registration System with a list of every individual care home apartment in Denmark [24]. The register provides the date of moving to a care home, the date of moving out (either to another care home or the date of death) and an encrypted care home name.
The Civil Registration System	This registry was founded in 1968 and contains general personal information on all Danish citizens [25]. From this register, we obtain information on date of birth, sex, and date of death (if relevant). A unique 10-digit identifier assigned to all individuals links to other national registers.
The Danish National Health Service Register	Since 1990, data on services provided by health contractors in the primary health care system is recorded in this register. As the data are collected for administrative purposes and are linked to the reimbursement of PCPs, the coverage is assumed to be high [26]. From this register, we collect individual information on registration with PCPs, dates of contact with PCPs and the out-of-hours service, and the types of services provided.
The Danish National Patient Register	Information on somatic in-patient activities has been collected since the establishment of the register in 1977. Since 1995, the register has included information on all in- and outpatient activities in both the somatic and psychiatric secondary health care systems [27]. From this register, we obtain information on the dates of hospital activities, the type of activity (e.g., admission or outpatient contact), and the urgency (planned or acute). For every contact, one primary and optional secondary diagnosis is recorded, and the diagnoses are registered according to the international classification of diseases (ICD-10).
The Danish National Prescription Registry	Individual-level data on all prescription medicine sold in Denmark has been recorded since 1995 [28]. Medicines are categorised according to the Anatomical Therapeutic Chemical Index (ATC codes) [29].