The aim of the CCCO study was to assess the prevalence of osteoporosis and osteopenia as well as associated risk factors. It was initiated in 2016 and is being conducted in nine centres across six cities. The cities are in the east, west, middle, south, north, and north-east of China. These sites were selected based on the local investigators' ability to administer the survey consistently, the availability of suitably qualified doctors to diagnose osteoporosis, and the presence of relatively fixed communities in those regions. Female residents aged 45-80 and male residents aged 50-80 were identified from permanent resident lists. Over 22,000 participants completed the baseline survey. Participants were re-surveyed annually for the first 5 years and then every 5 years thereafter.