Fig. 4.
Forest plot of the subgroup analyses stratified by type of studies (case- control, nested case- control and prospective cohorts). *One study selected, therefore P-values wasn’t calculated.
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.