Figure 1. (A/B): Age structure distribution map showed the age of the NSLBP occurrence is mainly concentrated in 31–55 years.
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.