Article History
Received: 9 July 2018
Accepted: 11 December 2018
First Online: 22 December 2018
Ethics approval and consent to participate
: The NHI data are secondary data and does not contain any private information. As the obtained data were anonymized and de-identified prior to analysis, the study protocol was not subjected to review by the ethics committee. This study follows the operational principles of the Declaration of Helsinki.
: All authors give consent to publish this article.
: None to declare.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.