Figure 1.
A flow diagram shows the screening and selection process of the studies through the different stages of the present systematic review. n: number of references/studies included or excluded.
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.