Figure 1.
The Preferred Reporting Item for Systematic Reviews and Meta-Analysis (PRISMA) flowchart of selection procedure for the studies.
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.