[Epidemiology of osteoporosis in Japan].

The high prevalence and tragic consequences of related fractures make osteoporosis a major burden on modern society. According to population-based epidemiologic studies, the estimated number of people with osteoporosis in Japan is 15 million, and only 20% of them are under treatment. Osteoporosis is a highly undertreated disease. The most recent incidence rates of hip fracture in Japan were 5.1 in 10,000 men and 18.1 in 10,000 women in 2007, and the number of patients are approximately 130 thousands which are 2.8-fold higher than those of the initial survey of 1987, but are still substantially less than rates in Caucasian populations. This increase in incidence rates can be explained by an increase in the elderly population. Data on the prevalence and incidence of vertebral fractures in Japan are vague compared with those of hip fracture. Prevalence rate of vertebral fracture was reported to be comparable to those in Caucasian populations, or even higher, and is approximately 30% in women aged 70s and 40% in those aged 80s. Hip fracture increases the mortality risk by approximately 10% or 20% during one year after the index fracture. Functional level of patients with hip fracture is deteriorated in 60% of them compared with pre-fracture level. Vertebral fracture also increases the risk of mortality even in radiographically determined ones. We currently have 13 million patients with osteoporosis in Japan among whom 130 thousands are suffered from hip fracture every year among whom 20 thousands die and 60 thousands experience functional decline. Effective preventive and therapeutic measures for osteoporosis should be conducted in more efficient ways. A greater role of the new guideline is expected than ever to promote preventive measures against osteoporosis and to increase physician's awareness to this disease.