1. Lung Health CenterandDivision of Pulmonary, Allergy and Critical Care MedicineUniversity of Alabama at BirminghamBirmingham, Alabama
2. Birmingham VA Medical CenterBirmingham, Alabama
3. Department of MedicineUniversity of California, San FranciscoSan Francisco, California
4. School of Public HealthUniversity of California, BerkeleyBerkeley, California
5. National Heart and Lung InstituteImperial College LondonLondon, United Kingdom