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.
CAT indicates COPD (chronic obstructive pulmonary disease) Assessment Test; mMRC, modified Medical Research Council Dyspnea Scale; ppb, parts per billion; SGRQ, St. George Respiratory Questionnaire. Error bars represent 95% CIs. P for interaction <.05 for analyses.
