Funding for this research was provided by:
Received: 23 November 2018
Accepted: 20 May 2019
First Online: 7 June 2019
Ethics approval and consent to participate
: This study was approved by SingHealth Centralized Institutional Review Board (CIRB 2016/2242) and informed written consent was obtained from all participants.
: Not applicable.
: The authors declare that they have no competing interests.