RevMan 5.3 Software was used to analyze the pooled effect. 
RevMan 5.3 Software
Studies were searched for on electronic search engines using Medline (PubMed), Cochrane central, Scopus and advanced Google Scholar from May 2015 to December 2015. 
Medline (PubMed)
Studies were searched for on electronic search engines using Medline (PubMed), Cochrane central, Scopus and advanced Google Scholar from May 2015 to December 2015. 
Cochrane central
Studies were searched for on electronic search engines using Medline (PubMed), Cochrane central, Scopus and advanced Google Scholar from May 2015 to December 2015. 
Scopus
Studies were searched for on electronic search engines using Medline (PubMed), Cochrane central, Scopus and advanced Google Scholar from May 2015 to December 2015. 
advanced Google Scholar