Funding for this research was provided by:
Berufsgenossenschaft für Transport und Verkehrswirtschaft (“BG Verkehr“), Hamburg (.)
Text and Data Mining valid from 2019-05-03
Received: 2 February 2019
Accepted: 16 April 2019
First Online: 3 May 2019
Ethics approval and consent to participate
: Taking part in this study was voluntarily. All participants gave their informed consent before taking part in this study. The study was approved by the Ethics Committee of the Hamburg Medical Association (no PV4395).
: Not applicable.
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.