Funding for this research was provided by:
Beijing Municipal Bureau of Health (2016-1-1075)
National Natural Science Foundation of China (81471166)
Received: 2 August 2017
Accepted: 7 February 2018
First Online: 27 February 2018
Ethics approval and consent to participate
: This study was approved by the ethics committee of Beijing Tiantan Hospital. This study was processed according to the principles expressed in the Declaration of Helsinki.
: Not applicable.
: The authors declare that they have no competing interests.