1. To establish a BMD reference database of Beijing's urban population, China.
2. To determine the prevalences and risk factors of osteoporosis and osteopenia in Beijing's urban population, China.
3. To describe the 25OHD level and estimate the prevalence of vitamin D insufficiency and deficiency of Beijing's urban population, China.
4. Estimation of the prevalence of osteoporotic fracture (vertebral) in over age of 60 of Beijing's urban population, China.

With one of the biggest populations in the world, China was heavily suffered from osteoporosis. The prevalence of osteoporosis in China even is increasing fast in recent years, which are especially notable in urban population. This change maybe due to the conditions including rapid economic growth, increase in life expectancy, and changes in lifestyle. Studies in 1998 including 13 separately small samples (no more than 1000 people) from 9 provinces in China showed that the prevalence of osteoporosis and osteopenia were 5.3-6.2% and 5.8-11.2%, respectively. These estimates were higher by approximately 1% than those reported in 1995. In 2002, according to DEXA results in connection with population census in 2000, Xiaoguang Cheng et al. took a survey in 600 people who were separately studied in previously 10 research projects and find that patients with osteoporosis account for approximately 6.97% of the total China population.

Although these studies have documented a remarkable increase in the prevalence of osteoporosis in China, these estimations were all based on small samples. No risk factors related with osteoporosis and osteopenia, esp. hypovitaminosis D on osteoporosis and osteopenia, have been analyzed yet. So it is impossible to make any forecast of osteoporosis or give any instruction for intervention.

Thus this study designed to provide current and reliable data on the prevalence of osteoporosis and osteopenia and associated risk factors correlation coefficients in the Beijing's urban adult population.

Inclusion Criteria:

• 20 to 79 residents in urban Beijing, China.

Exclusion Criteria:

The study will comprise 10,000 people aging from 20 to 79 residing in urban Beijing, China. All of them are members of Beijing Municipal Health Insurance (Beijing is a city that buy medical insurances for all of its residents).