1. Department of Endocrinology, Air Force Medical Center, People's Liberation Army, Beijing, China
2. Department of Geriatrics, Air Force Medical Center, People's Liberation Army, Beijing, China
3. BMJ Publishing Group, BMA House, London, United Kingdom
4. Edge Hill University Medical School, Edge Hill University, Lancashire, United Kingdom
5. Department of Medical Research, Air Force Medical Center, People's Liberation Army, Beijing, China
6. Department of Orthopedics, Air Force Medical Center, People's Liberation Army, Beijing, China
7. Teaching and Research Division of Internal Medicine, Air Force Medical Center, People's Liberation Army, Beijing, China