Figure 1.
The flow chart of study selection has been designed under the guidance of the Preferred Reporting Items for Systematic Reviews and Meta-analysis Protocols).
Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.