Huang, Shanshan
Shen, Qing
Yang, Ruoqing
Lai, Heng
Zhang, Jing
Article History
Received: 8 January 2018
Accepted: 14 July 2018
First Online: 25 July 2018
Compliance with ethical standards
:
: The authors declare that they have no conflicts of interest.
: As the study was a meta-analysis based on the existing population-based studies, we did not apply for the approval of institutional review board.