This is a multicenter cohort study on osteoporosis in nine cities of China which locate in the east, south, north, west, middle of China. At least 3000 middle-aged and elderly permanent residents (women aged from 45 to 79, and men aged from 50 to 79) in every city will be enrolled. Residents with severe mental diseases, physical diseases or acute infectious diseases who could not cooperate with the survey as well as lactating or pregnant women were excluded. All the enrolled residents who signed informed consent will finish questionnaire including demographic characteristics, history of smoking, alcohol drinking, falls and fracture, family genetic history, chronic diseases and medicine,diary and physical practice，stool and urine status. Osteoporosis risk, health status, constitution of traditional Chinese medicine (TCM),symptoms of kidney yang deficiency in TCM，living environment,sweating status will be evaluated. Fasting blood glucose test and other blood tests for liver and kidney function,bone metabolism，vitamins，vitamin D metabolism and transportation as well as calcium and phosphate metabolism, will be performed. Bone mineral density and physical examinations (height, weight, waist circumference, hip circumference,grip,sit-to-stand test, tongue coating and pulse) will also be performed at enrollment and every two years after enrollment. DNA of blood cells will be preserved for specific study such as SNP analyses.Tongue coating and feces will be preserved for microflora analyses.