Figure 1.
PRISMA flow chart depicting the number of papers identified, screened and included in the overview. *A list of excluded studies with reasons are provided in online supplemental appendix 2.
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.