1. Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
2. Department of Geriatrics and Institute of Geriatrics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China; and
3. Department of Pulmonary, Allergy, and Critical Care Medicine, the Second Affiliated Hospital, Tianjin University of Traditional Chinese Medicine, Tianjin, China