1. Department of Preventive Medicine, Rush University Medical Center, Chicago, Illinois, USA;
2. Department of Preventive Medicine, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA;
3. American Lung Association, Springfield, Illinois, USA;
4. Department of Medical Social Sciences, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA;
5. Division of Pulmonary and Critical Care Medicine, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA