Visits and Data Collection: Participants were/will be visited every three years by invited to the School of Public Health, Sun Yat-sen University. At each visit, face-to-face interviews, specimen collection, anthropometric measurements, DXA scanning, ultrasonography evaluation were/will be conducted. Up to May 2017, 3400 subjects completed their 2nd visits, and 2380 attended their 3rd visits. It is planned to follow up the participant in person for at least 15 years.