Funding for this research was provided by:
The Research Council of Norway (237784)
Received: 23 November 2018
Accepted: 14 November 2019
First Online: 27 November 2019
Ethics approval and consent to participate
: The study was conducted in accordance with the ethical principles outlined in the Declaration of Helsinki. The present study relies entirely on pre-existing data from hospital registers. Given the pre-existing nature of the data, we were not able to collect informed consent. However, the data were anonymized by the hospital before being transferred to the researchers. Therefore, no consent to participate was required for this study. The participating hospital permitted access to the data and ensured that the data were anonymized prior to being transferred. The research has also been reported to the Norwegian Social Science Data Service (NSD), thereby ensuring compliance with all ethical requirements applying to data acquisition, data storage and data management (ref: 40900/3/LT). NSD is the data protection authority for research applicable to all Norwegian universities and university colleges, in addition to hospitals and research centers. In Norway, submitting the research for ethical approval only to NSD is sufficient. In cases where research needs further ethical approval, NSD will notify the researchers that they are required to obtain ethical consent from the Norwegian Data Inspectorate. Further ethical approval was not required for this project.
: Not applicable.
: The authors declare that they have no competing interests.