Received: 9 March 2020
Accepted: 19 May 2020
First Online: 1 June 2020
Ethics approval and consent to participate
: The regional ethics committee and the Norwegian Data Protection Authority approved the study before we got access to the relevant data from our national health registers. Norwegian health registers are regulated by Norwegian low (Helseregisterloven¸ LOV-2014-06-20-43) and no consent to participate is needed from the individuals contributing data to our dataset.
: Not applicable.
: The authors declare that there are no conflicts of interest.