Figure 2.
Risk of bias for the studies included in the meta-analysis. (a) Risk of bias graph. (b)Risk of bias summary.
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.