H. Orimo

Despite lower femoral neck bone mass, Japanese women have a substantially lower incidence of hip fracture than North American whites. Reasons for this discrepancy were sought in a study of 57 Japanese and 119 white American women aged 50-79. All women were in good health. Bone mineral content (BMC) in the femoral neck, femoral neck length (NL), femoral neck angle (theta), cross-sectional moment of inertia (CSMI), safety factor (SF), and fall index (FI) were calculated using dual x-ray absorptiometry. Height and weight were greater in Americans than in Japanese (1.62 versus 1.52 m; p < 0.0001 and 66.0 versus 49.4 kg; p < 0.0001, respectively). Mean BMC in the femoral neck and CSMI were greater in Americans than in Japanese (3.91 versus 3.02 g; p < 0.0001 and 0.99 versus 0.57 cm4; p < 0.0001, respectively). NL was longer in Americans (5.6 versus 4.4 cm; p < 0.0001) and theta was larger in Americans (130 versus 128 degrees; p < 0.01), whereas SF and FI were less in Americans than in Japanese (3.41 versus 5.12; p < 0.0001 and 1.00 versus 1.40; p < 0.0001, respectively). These results indicate that despite lower bone mass, Japanese women have lower risks of structural failure in the femoral neck, attributable primarily to shorter femoral necks and, to a lesser degree, a smaller femoral neck angle. Geometric characteristics of the femoral neck in Japanese women are associated with their lower hip fracture risk, and the measurement of proximal femoral geometry, combined with bone mass, may provide further clinical information about the risk of hip fracture.

UNLABELLED: The present study estimated the 10-year probability using the Japanese version of WHO fracture risk assessment tool (FRAX) in order to determine fracture probabilities that correspond to intervention thresholds currently used in Japan and to resolve some issues for its use in Japan. INTRODUCTION: The objective of the present study was to evaluate a Japanese version of the WHO fracture risk assessment (FRAX) tool to compute 10-year probabilities of osteoporotic fracture in Japanese men and women. Since lumbar spine bone mineral density (BMD) is used preferentially as a site for assessment, and densitometers use Japanese reference data, a second aim was to investigate the suitability and impact of this practice in Japan. METHODS: Fracture probabilities were computed from published data on the fracture and death hazards in Japan. Probabilities took account of age, sex, the presence of clinical risk factors and femoral neck BMD. Fracture probabilities were determined that were equivalent to intervention thresholds currently used in Japan. The difference between T-scores derived from international reference data and that using Japanese-specific normal ranges was estimated from published sources. The gradient of risk of BMD for fracture in Japan was compared to that for BMD at the lumbar spine in the Hiroshima cohort. RESULTS: The 10-year probabilities of a major osteoporosis-related fracture that corresponded to current intervention thresholds ranged from approximately 5% at the age of 50 years to more than 20% at the age of 80 years. The use of femoral neck BMD predicts fracture as well as or better than BMD tests at the lumbar spine. There were small differences in T-scores between those used for the model and those derived from a Japanese reference population. CONCLUSIONS: The FRAX mark tool has been used to determine possible thresholds for therapeutic intervention, based on equivalence of risk with current guidelines. The approach will need to be supported by appropriate health economic analyses. Femoral neck BMD is suitable for the prediction of fracture risk among Japanese. However, when applying the FRAX model to Japan, T-scores and Z-scores should be converted to those derived from the international reference.

UNLABELLED: We estimated the number of hip fracture patients in 2012 in Japan and investigated the trends in incidence during a 25-year period from 1987 to 2012. Despite the increasing number of patients, the incidence of hip fracture in both men and women aged 70-79 years showed the possibility of decline. INTRODUCTION: The objectives of this study were to estimate the number of hip fracture patients in 2012, to investigate the trends in incidence during a 25-year period from 1987 to 2012, and to determine the regional differences in Japan. METHODS: Data were collected through a nationwide survey based on hospitals by a mail-in survey. Hip fracture incidences by sex and age and standardized incidence ratios by region were calculated. RESULTS: The estimated numbers of new hip fracture patients in 2012 were 175,700 in total (95 % CI 170,300-181,100), 37,600 (36,600-38,600) for men and 138,100 (134,300-141,900) for women. The incidence rates in both men and women aged 70-79 years were the lowest in the 20-year period from 1992 to 2012. The incidence was higher in western areas of Japan than that in eastern areas in both men and women; however, the difference in the incidence of hip fracture between western and eastern areas is becoming smaller. CONCLUSIONS: Despite the increasing number of new patients, the incidence of hip fracture in both men and women aged 70-79 years showed the possibility of decline. The exact reasons for this are unknown, but various drugs for improving bone mineral density or preventing hip fracture might have influenced the results. A decrease in the differences in nutrient intake levels might explain some of the change in regional differences in Japan.