[Epidemiology of bone and joint disease - the present and future - . Epidemiology of osteoporosis and osteoporotic fracture in Japan].

: Osteoporosis is a major burden on modern society because of its high prevalence and tragic consequences due to fractures. According to population-based epidemiologic studies, number of people with osteoporosis in Japan was estimated to be 13 million in 2005, and only 20% of them were under treatment. Osteoporosis is a highly undertreated disease. Number of hip fractures occurred in Japan in 2007 was approximately 130 thousands which were 2.8-fold greater than those in 1987. This increase can be explained by an increase in the elderly population. Prevalence rate of vertebral fracture was reported to be approximately 30% in women aged 70s and 40% in those aged 80s. Fracture risk assessment in individuals is essential for osteoporosis management. To improve prediction accuracy for major osteoporotic fractures, FRAX(®) model including clinical risk factors was developed. Predicted risk of major osteoporotic fractures for Japanese women by FRAX(®) were not significantly different from observed risk in the Japanese Population-based Osteoporosis (JPOS) Cohort Study, and FRAX(®) model without bone mineral density (BMD) showed a similar validity to FRAX(®) model with BMD. This suggests that FRAX(®) without BMD may be used as a screening tool for people at increased risk of fractures in community. However, FRAX(®) should be improved further in combination with new bone strength indices. Epidemiology should play a great role in developing and evaluating such improvement in fracture risk assessment.