Text and Data Mining valid from 2019-01-11
Received: 6 July 2018
Accepted: 26 December 2018
First Online: 11 January 2019
Ethics approval and consent to participate
: The study protocol was approved by the Ethics Committee of Oulu University Hospital. Because the study was epidemiological without any interventions, the requirement for informed consent was waived.
: Not applicable.
: The authors declare that they have no competing interests.
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