Data were analyzed by STATA 13.0 (Stata Corporation, College Station, TX, USA).



STATA
A meta-analysis was performed using PubMed, Web of Science, Embase and Cochrane library to identify relevant studies. 
PubMed
A meta-analysis was performed using PubMed, Web of Science, Embase and Cochrane library to identify relevant studies. 
Web of Science
A meta-analysis was performed using PubMed, Web of Science, Embase and Cochrane library to identify relevant studies. 
Embase
A meta-analysis was performed using PubMed, Web of Science, Embase and Cochrane library to identify relevant studies. 
Cochrane library