Received: 12 November 2019
Accepted: 8 January 2020
First Online: 20 January 2020
Ethics approval and consent to participate
: The study was conducted in accordance with the declaration of Helsinki and all subjects gave written informed consent to participate. The Ethics Committee of the Canton of Zurich approved the study (EK-ZH-NR: 1734 and 2011–0106) and the study is registered at ExternalRef removed, NCT01527773.
: Not applicable.
: The authors declare that they have no competing interests.