1. Department of Anesthesiology, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, Guangdong Province 510120, P. R. China
2. Geriatric Anesthesia Research Unit, Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA
3. Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA
4. College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, P. R. China
5. Department of Anesthesia, Shanghai 10th People’s Hospital, Anesthesia and Brain Research Institute, Tongji University, Shanghai 200072, P. R. China
6. Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA 02115, USA
7. Department of Psychiatry, Shanghai 10th People’s Hospital, Anesthesia and Brain Research Institute, Tongji University, Shanghai 200072, P. R. China
8. Divisions of General Medicine and Primary Care and Gerontology, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02215, USA