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.
aExclusions are ordered by frequency rather than actual sequence applied.
bExcluded from Cox proportional hazards models because of missing data on hospital characteristics and National Institutes of Health Stroke Scale score.
