Figure 1.
Flow chart of the study selection process. A systematic review yielded 433 reports. After the removal of duplicates and the application of inclusion and exclusion criteria, 15 studies were included in the meta-analysis.
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.