Received: 16 May 2019
Accepted: 22 August 2019
First Online: 13 November 2019
Ethics approval and consent to participate
: This study forms part of larger study [CitationRef removed] that was submitted to the Ethics Committee of the Vrij Universiteit Medical Centre, Amsterdam (Medical Ethics Committee VuMc, email: ExternalRef removed, submission reference number: 2014/030. The need for approval was deemed unnecessary, according to national regulations [CitationRef removed]. Therefore, the Committee waived the need for ethics approval.Consent to participate was implied by completion and return of the questionnaire.
: Not applicable.
: The authors declare that they have no competing interests.