[Epidemiology of osteoporosis: gender differences].

Although no sex difference is observed in bone mineral density (BMD) during the first five decades of life, BMD is lower in females than in males at the age of 50 and older. The prevalence of osteoporosis and the incidence of osteoporosis-related bone fracture in females are two-fold or more higher than in males. BMD is an important predictor of bone fracture risk in both sexes, and there is no sex difference in its predictability. After adjustment is made for BMD, the sex difference in the incidence of vertebral fracture almost disappears. The sex difference in BMD virtually explains the sex difference in the incidence of spine fracture.