1. Geriatric Anesthesia Research Unit, Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
2. Department of Anesthesiology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, P.R. China
3. Department of Veterans Affairs, Medical Research and Development Service and Geriatric Research, Education and Clinical Center, Bedford, MA, USA