Bone strength is predominantly determined by bone density, but bone microarchitecture also plays an important role. We examined whether trabecular bone score (TBS) predicts the risk of vertebral fractures in a Japanese female cohort. Of 1950 randomly selected women aged 15 to 79 years, we analyzed data from 665 women aged 50 years and older, who completed the baseline study and at least one follow-up survey over 10 years, and who had no conditions affecting bone metabolism. Each survey included spinal imaging by dual-energy X-ray absorptiometry (DXA) for vertebral fracture assessment and spine areal bone mineral density (aBMD) measurement. TBS was obtained from spine DXA scans archived in the baseline study. Incident vertebral fracture was determined when vertebral height was reduced by 20% or more and satisfied McCloskey-Kanis criteria or Genant's grade 2 fracture at follow-up. Among eligible women (mean age 64.1 AE 8.1 years), 92 suffered incident vertebral fractures (16.7/10 3 person-years). These women were older with lower aBMD and TBS values relative to those without fractures. The unadjusted odds ratio of vertebral fractures for one standard deviation decrease in TBS was 1.98 (95% confidence interval [CI] 1.56, 2.51) and remained significant (1.64, 95% CI 1.25, 2.15) after adjusting for aBMD. The area under the receiver operating characteristic curve of TBS and aBMD combined was 0.700 for vertebral fracture prediction and was not significantly greater than that of aBMD alone (0.673). However, reclassification improvement measures indicated that TBS and aBMD combined significantly improved risk prediction accuracy compared with aBMD alone. Further inclusion of age and prevalent vertebral deformity in the model improved vertebral fracture prediction, and TBS remained significant in the model. Thus, lower TBS was associated with higher risk of vertebral fracture over 10 years independently of aBMD and clinical risk factors including prevalent vertebral deformity. TBS could effectively improve fracture risk assessment in clinical settings.

Low bone mineral density (BMD) is one of the most important elements for the diagnosis of osteoporosis and screening people with higher risk of fractures. To establish the criterion value of BMD for the diagnosis of osteoporosis and to estimate the prevalence rate of osteoporosis in Japanese women, we performed a Japanese population-based osteoporosis (JPOS) study. The subjects were 4550 women aged 15 through 79 years randomly selected from seven municipalities throughout Japan. The sample size was determined to ensure that the observed mean BMD would remain within 2.5% from the real value with a probability of 0.95 in each of the 5-year age groups. The study comprised bone mass measurements by dual-energy X-ray absorptiometry at the spine (L2-4), hip and distal forearm, body size measurements and detailed interviews on medical and gynecologic history. After excluding those subjects with apparent or suggested abnormalities affecting bone mass from 3985 women (87.6%) who completed the study, 3465 women remained and served as the subjects. We present 5-year age-specific mean values of BMD and cut-off values for the diagnosis of osteoporosis according to World Health Organization (WHO) and the Japanese Society of Bone and Mineral Research (JSBMR) criteria. The cut-off levels at the spine and the distal radius proposed in this study were similar to those proposed by the JSBMR but the cut-off level at the femoral neck in this study was 4.7% higher than that of the JSBMR. The prevalence rates of osteoporosis according to WHO criteria in the present subjects aged 50 through 79 years were calculated as 38.0% at the spine, 11.6% at the femoral neck and 56.8% at the distal one-third site of the radius, and those in the Japanese female population of the same age were estimated to be 35.1%, 9.4% and 51.2%, respectively. A fivefold difference was observed among the prevalence rates at different skeletal sites, which suggests that the different definitions of osteoporosis should be established for the different skeletal sites. The prevalence rate diagnosed at the femoral neck seemed to be lower in the present study than those reported for Caucasians. This might account for a lower incidence rate of hip fracture in Japanese women.

Japanese fermented soybeans (natto in Japanese), which contain a large amount of menaquinone-7, may help prevent the development of osteoporosis. We assessed the possibility of an association between habitual natto intake and bone mineral density (BMD) and BMD change over time in healthy Japanese women who participated in a large representative cohort study (Japanese Population-based Osteoporosis Study: JPOS study). The BMD was measured at the spine, hip, and forearm in 944 women (20-79 y old) at baseline and at a follow-up conducted 3 y later. Dietary natto intake was assessed by a FFQ on both occasions. Additional covariates including age, height, weight, lifestyle factors, dietary calcium intake, and the intake of other soybean products, were also measured. The total hip BMD at baseline increased (P for trend = 0.0034) with increasing habitual natto intake in the postmenopausal women, although this was not the case at other skeletal sites. There were significant positive associations between natto intake and the rates of changes in BMD at the femoral neck (P < 0.0001) and at the distal third of the radius (P = 0.0002) in the postmenopausal women. The association in the femoral neck persisted even after adjusting for covariates. No significant association was observed between the intake of tofu or other soybean products and the rate of BMD change in the postmenopausal women. Natto intake may help prevent postmenopausal bone loss through the effects of menaquinone 7 or bioavailable isoflavones, which are more abundant in natto than in other soybean products.

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The present study was conducted as a part of the Japanese Population-based Osteoporosis (JPOS) Study to establish reference values on the biochemical markers of bone turnover in the general Japanese female population over an applicable age range. The study recruited 3250 women aged 15-79 years, randomly selected from five municipalities throughout Japan, and obtained measurements of serum osteocalcin (OC) and bone-specific alkaline phosphatase (BAP); free and total forms of immunoreactive deoxypyridinoline, free pyridinolines and type I collagen cross-linked C-terminal telopeptide (CTx) in urine; serum intact parathyroid hormone (PTH) and 1,25 dihydroxy vitamin D (1,25 (OH)2D); and bone density at the spine, hip and distal forearm. After excluding subjects with apparent or suggested abnormalities affecting bone mass, 2535 (78%) subjects were further analyzed. The authors presented 5-year age-specific mean values of the markers and mean marker levels derived from women aged 30-44 years with normal bone density as a healthy young adult reference. Values of the markers decreased with increasing age before the age of 40, increased steeply among subjects in their 50s, and remained elevated in the elderly. Serum calcium, phosphorus, PTH and 1,25 (OH)2D levels were higher in postmenopausal women than in premenopausal women. However, 1,25 (OH)2D was lower among early postmenopausal subjects. The levels of OC, BAP, CTx, PTH and 1,25(OH)2D were significantly greater for women with osteoporosis than for those without. The diagnostic value of the markers was limited as the sensitivity and specificity ranged from 55% to 60%. These findings will aid health professionals in the correct assessment of bone turnover status in Japanese women over a wide range of age.