Funding for this research was provided by:
Received: 21 February 2018
Accepted: 8 June 2018
First Online: 18 June 2018
Ethics approval and consent to participate
: This study was approved by the VU University Medical Center Amsterdam Ethics Committee on 9 July 2014, reference number 2014.305. It is conducted according to the principles of the Declaration of Helsinki (version 2013). This study involves a secondary analysis of previously collected data and the ethics and consent were obtained during the original study. Informed consent was obtained from all participants.
: The authors declare that they have no competing interests.
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