Funding for this research was provided by:
Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung (CR13I1_156274/1)
Received: 24 December 2018
Accepted: 5 June 2019
First Online: 13 June 2019
Ethics approval and consent to participate
: The study was approved by the cantonal ethics committee Zurich (No 2015–0350). All study participants provided verbal consent. The cantonal ethic committee approved this procedure.
: Not applicable.
: The authors declare that they have no competing interests.