1. The Center of Gerontology and Geriatrics (National Clinical Research Center for Geriatrics), West China Hospital, Sichuan University, Chengdu, China
2. Longitudinal Studies Section, The National Institute on Aging, Baltimore, Maryland, USA
3. Department of Health Policy and Management, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
4. Center on Aging and Health, Johns Hopkins Medical Institutions, Baltimore, Maryland, USA
5. Division of Geriatric Medicine and Gerontology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA