Funding for this research was provided by:
National Heart, Lung, and Blood Institute (U19 AI135964 and R56 HL135124)
National Institutes of Health (ES013995 and HL071643, AG049665, HL048129, HL071643, and HL085534, HL125940)
U.S. Department of Veterans Affairs (BX000201)
Office of the Assistant Secretary of Defense for Health Affairs (W81XWH-15-1-0215)
Received: 28 August 2018
Accepted: 7 November 2018
First Online: 26 November 2018
Ethics approval and consent to participate
: Approval for this study was obtained by the institutional review boards at Northwestern University (Chicago, IL, USA) and Instituto Nacional de Enfermedades Respiratorias Ismael Cosio Villegas (INER; Mexico City, Mexico). Patients and controls were explained about the study and signed a consent letter.
: Not applicable
: The authors declare that they have no competing interests.
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