Spinal trabecular bone loss and fracture in American and Japanese women

Androgen-deprivation therapy and the risk of newly developed fractures in patients with prostate cancer: a nationwide cohort study in Korea

We evaluated the risk of osteoporosis and fractures associated with androgen deprivation therapy (ADT) use and duration in men with prostate cancer. From the nationwide claims database in South Korea, a total of 218,203 men with prostate cancer were identified between 2008 and 2017. After applying the inclusion and exclusion criteria, a total of 144,670 patients were included in the analysis. To adjust for comorbidities between cohorts, 1:1 propensity score matching was used. Cox proportional hazard regression models were used to estimate adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) of events associated with ADT, after controlling for potential confounding factors. In the matched cohort, there were differences in the incidence of newly developed osteoporosis (8.79% in the ADT group vs. 7.08% in the non-ADT group, p < 0.0001) and fractures (8.12% in the ADT group vs. 5.04% in the non-ADT group, p < 0.0001). Age-adjusted Cox regression analysis revealed that the ADT group had a significantly higher risk of osteoporosis (HR, 1.381; 95% CI, 1.305–1.461; p < 0.0001) and fractures (HR, 1.815; 95% CI, 1.703–1.935; p < 0.0001) compared to the non-ADT group. Furthermore, the risk of osteoporosis and fractures increased as the duration of ADT increased. The ADT was associated with an increased risk of osteoporosis and fractures in prostate cancer patients. Clinicians who administer ADT for patients with prostate cancer should always be mindful of the risk of osteoporosis and fracture, avoid unnecessary ADT, and perform regular bone health check-ups.

Sexual Dimorphism and the Origins of Human Spinal Health

Recent observations indicate that the cross-sectional area (CSA) of vertebral bodies is on average 10% smaller in healthy newborn girls than in newborn boys, a striking difference that increases during infancy and puberty and is greatest by the time of sexual and skeletal maturity. The smaller CSA of female vertebrae is associated with greater spinal flexibility and could represent the human adaptation to fetal load in bipedal posture. Unfortunately, it also imparts a mechanical disadvantage that increases stress within the vertebrae for all physical activities. This review summarizes the potential endocrine, genetic, and environmental determinants of vertebral cross-sectional growth and current knowledge of the association between the small female vertebrae and greater risk for a broad array of spinal conditions across the lifespan.

Comparison of vertebral and femoral bone mineral density in adult females

[Purpose] This study assessed vertebral and femoral bone mineral density in adult females. [Subjects and Methods] A total of 314 females in their 40s to 70s were divided into normal, osteopenia, and osteoporosis groups and their vertebral and femoral bone mineral densities were compared. [Results] Comparisons of T scores revealed significant differences among measurements of the third lumbar vertebra, femoral neck, Ward's triangle, and femoral trochanter. Pearson correlation coefficients were used to assess differences between the vertebral and femoral measurements, and significant differences and positive correlations were observed among third lumbar vertebra, femoral neck, Ward's triangle, and femur trochanter in the normal group. [Conclusion] Females in the normal, osteopenia, and osteoporosis groups showed significant differences in their third lumbar vertebrae. The lack of significant differences among measurements in the osteoporosis group in this study suggests that patients with osteoporosis require careful and accurate diagnosis.

Effect of aromatase inhibitors on bone mineral density in a Japanese breast cancer population

We retrospectively analyzed the bone mineral density (BMD) of postmenopausal Japanese women taking an aromatase inhibitor (AI), exemestane, anastrozole or letrozole, and calculated the decrease rate constant of BMD in each individual to compare the influence of the three AIs on BMD. We also aimed to evaluate the preventive effect of bisphosphonates (BPs) on the AI-induced decrease in BMD. The decrease rate constant of BMD (k(e)) in each individual was determined as a slope of linear regression of the relationship between time and logarithm of BMD value in each patient during the AI therapy. To compensate for the age-related change in BMD level, we estimated the age-related decrease rate constant of BMD (ke,0) in healthy Japanese postmenopausal women from the literature. AIs decreased BMD with a ke value of -0.0329 yr(-1), which was 4.7-fold larger than the k(e,₀) value of -0.00699 yr(-1). No significant difference was detected in the influence on BMD among AIs. Co-administration of BP ameliorated the ke value to -0.0117 yr(-1), a value similar to k(e,₀). The influence of AIs on BMD was quantitatively evaluated by using the decrease rate constant of BMD (k(e)). The present study also suggests that BPs may be useful to prevent the decrease in BMD induced by AIs.

Effect of low-dose calcium supplements on bone loss in perimenopausal and postmenopausal Asian women: a randomized controlled trial

Current standard-dose calcium supplements (eg, 1000 mg/d) may increase the risk for cardiovascular events. Effectiveness of lower-dose supplements in preventing bone loss should thus be considered. This study aimed to assess whether calcium supplements of 500 or 250 mg/d effectively prevent bone loss in perimenopausal and postmenopausal Japanese women. We recruited 450 Japanese women between 50 and 75 years of age. They were randomly assigned to receive 500 mg of calcium (as calcium carbonate), 250 mg of calcium, or placebo daily. Medical examinations conducted three times over a 2-year follow-up period assessed bone mineral density (BMD) of the lumbar spine and femoral neck. One-factor repeated measures ANOVA was used for statistical tests. Subgroup analyses were also conducted. Average total daily calcium intake at baseline for the 418 subjects who underwent follow-up examinations was 493 mg/d. Intention-to-treat analysis showed less dramatic decreases in spinal BMD for the 500-mg/d calcium supplement group compared to the placebo group (1.2% difference over 2 years, p = 0.027). Per-protocol analysis (≥80% compliance) revealed that spinal BMD for the 500-mg/d and 250-mg/d calcium supplement groups decreased less than the placebo group (1.6%, p = 0.010 and 1.0%, p = 0.078, respectively), and that femoral neck BMD for the 500-mg/d calcium supplement group decreased less relative to the placebo group (1.0%, p = 0.077). A low-dose calcium supplement of 500 mg/d can effectively slow lumbar spine bone loss in perimenopausal and postmenopausal women with habitually low calcium intake, but its effect on the femoral neck is less certain. Calcium supplementation dosage should thus be reassessed. (Clinical Trials Registry number: UMIN000001176).

Bone and the perimenopause

Loss of ovarian function has a profound impact on female skeletal health. Bone mineral density findings from the Study of Women's Health Across the Nation demonstrate an accelerated rate of bone loss during the menopausal transition. The greatest reduction occurs in the year before the final menstrual period and the first 2 years thereafter. Clinical management includes maintenance of adequate dietary calcium and vitamin D intake, attention to modifiable risk factors, and osteoporosis screening. Indications, benefits, and risks of pharmacologic osteoporosis therapy should be assessed individually; there are currently no established guidelines addressing the treatment and prevention of osteoporosis in perimenopausal women.

Tibolone increases bone mineral density but also relapse in breast cancer survivors: LIBERATE trial bone substudy

Introduction

The Livial Intervention Following Breast Cancer: Efficacy, Recurrence and Tolerability Endpoints (LIBERATE: Clinical http://Trials.gov number NCT00408863), a randomized, placebo-controlled, double-blind trial that demonstrated that tibolone (Livial), a tissue-selective hormone-replacement therapy (HRT), increased breast cancer (BC) recurrence HR 1.40 (95% CI, 1.14 to 1.70; P = 0.001). A subgroup of women was entered into a study of bone mineral density (BMD).

Methods

Women with surgically excised primary BC (T1-3, N0-2, M-0) within the last 5 years, complaining of vasomotor symptoms, were assigned to tibolone, 2.5 mg daily, or placebo treatment for a maximum of 5 years. The BMD substudy enrolled 763 patients, using dual-energy X-ray absorptiometry (DXA) scanning at baseline and at 2 years.

Results

In the bone substudy, 699 of 763 women were eligible (345 allocated to tibolone, and 354, to placebo). After undergoing DXA scans, 300 (43%) women had normal BMD; 317 (45%), osteopenia; and 82 (11.7%), osteoporosis. Low body-mass index (P < 0.001), Asian race (P < 0.001), and late age at menarche (P < 0.04) predicted low bone mass at baseline. Tibolone increased BMD by 3.2% at the lumbar spine and 2.9% at the hip compared with placebo (both P < 0.001). The majority of fractures (55%) occurred in osteopenic patients. Women with normal BMD had increased recurrence with tibolone, 22 (15.6%) of 141 compared with placebo, 11 (6.9%) of 159 (P = 0.016), whereas no increased BC recurrence was seen in women with low BMD; 15 (7.4%) of 204 taking tibolone versus 13 (6.7%) of 195 taking placebo.

Conclusions

Tibolone is contraindicated after BC treatment, as it increases BMD and BC recurrence. Risk of BC recurrence was elevated in BC women with normal BMD (compared with low) who took tibolone.

Recent progress in bone imaging for osteoporosis research

Advances in bone imaging techniques have provided tools for analyzing bone structure at the macro-, micro- and nano-level. Quantitative assessment of macrostructure can be achieved using dual X-ray absorptiometry (DXA) and quantitative computed tomography (QCT), particularly volumetric quantitative CT (vQCT). In vivo quantitative techniques for assessing the microstructure of trabecular bone non-invasively and non-destructively include high-resolution CT (HR-CT) and high-resolution magnetic resonance (HR-MR). Compared with MR imaging, CT-based techniques have the advantage of directly visualizing the bone in the axial skeleton, with high spatial resolution, but the disadvantage of delivering a considerable radiation dose. Micro-CT (μCT), which provides a higher resolution of the microstructure and is principally applicable in vitro, has undergone technological advances such that it is now able to elucidate the physiological skeletal change mechanisms associated with aging and determine the effects of therapeutic intervention on the bone microstructure. In particular, synchrotron μCT (SR-CT) provides a more detailed view of trabecular structure at the nano-level. For the assessment of hip geometry, DXA-based hip structure analysis (HSA) and CT-based HSA have been developed. DXA-based HSA is a convenient tool for analyzing biomechanical properties and for assuming cross-sectional hip geometry based on two-dimensional (2D) data, whereas CT-based HSA provides these parameters three-dimensionally in robust relationship with biomechanical properties, at the cost of greater radiation exposure and the lengthy time required for the analytical procedure. Further progress in bone imaging technology is promising to bring new aspects of bone structure in relation to bone strength to light, and to establish a means for analyzing bone structural properties in the everyday clinical setting.

Densitometric and geometric measurement of the proximal femur in elderly women with and without osteoporotic vertebral fractures by volumetric quantitative multi-slice CT

There is a lack of research on volumetric multi-slice CT (MSCT) application in hip densitometric assessment and geometric measures in elderly women with osteoporotic vertebral fractures. A total of 237 elderly women were divided into three groups based on BMD values of the lumbar spine (AP-SPINE) and/or the femoral neck (NECK) by dual energy X-ray absorptiometry (DXA): osteoporosis with (OP_FX, 53 cases) or without vertebral fracture (OP_NONFX, 94 cases), or normal BMD (CONTROL, 90 cases). Volumetric BMD of trabecular bone (TRAB), integral bone (INTGL) and cortical bone (CORT) with neck axis length (NAL) and minimum cross-section area (mCSA) measures of the left femoral neck were calculated, respectively, by using OsteoCAD software based on MSCT scans of the abdominal-pelvic region of all participants, then the index of femoral neck strength (FNSI) was estimated. The values of TRAB, CORT and INTGL of OP_FX were significantly lower than those of OP_NONFX, with the decrease in 6.8-21.8%, as well as being lower than those in CONTROL, whereas no significant differences in the values of AP-SPINE and NECK were found between OP_FX and OP_NONFX. No significant difference of the value of mCSA was found among these three groups. The NAL value of OP_NONFX was larger than that of CONTROL. FNSI of femoral neck in OP_FX (0.42 ± 0.15 g(2)/cm(4)) was significantly lower than OP_NONFX (0.50 ± 0.14 g(2)/cm(4)) (p < 0.05). vQCT measurement seemed to be more effective than DXA in evaluating hip densitometric changes and discriminating osteoporotic elderly subjects with fractured vertebrae from the non-fractured in a group of Chinese women.

Assessment of volumetric bone mineral density of the femoral neck in postmenopausal women with and without vertebral fractures using quantitative multi-slice CT

OBJECTIVE

To demonstrate the validity and reliability of volumetric quantitative computed tomography (vQCT) with multi-slice computed tomography (MSCT) and dual energy X-ray absorptiometry (DXA) for hip bone mineral density (BMD) measurements, and to compare the differences between the two techniques in discriminating postmenopausal women with osteoporosis-related vertebral fractures from those without.

METHODS

Ninety subjects were enrolled and divided into three groups based on the BMD values of the lumbar spine and/or the femoral neck by DXA. Groups 1 and 2 consisted of postmenopausal women with BMD changes <-2SD, with and without radiographically confirmed vertebral fracture (n=11 and 33, respectively). Group 3 comprised normal controls with BMD changes > or =-1SD (n=46). Post-MSCT (GE, LightSpeed16) scan reconstructed images of the abdominal-pelvic region, 1.25 mm thick per slice, were processed by OsteoCAD software to calculate the following parameters: volumetric BMD values of trabecular bone (TRAB), cortical bone (CORT), and integral bone (INTGL) of the left femoral neck, femoral neck axis length (NAL), and minimum cross-section area (mCSA). DXA BMD measurements of the lumbar spine (AP-SPINE) and the left femoral neck (NECK) also were performed for each subject.

RESULTS

The values of all seven parameters were significantly lower in subjects of Groups 1 and 2 than in normal postmenopausal women (P<0.05, respectively). Comparing Groups 1 and 2, 3D-TRAB and 3D-INTGL were significantly lower in postmenopausal women with vertebral fracture(s) [(109.8+/-9.61) and (243.3+/-33.0) mg/cm3, respectively] than in those without [(148.9+/-7.47) and (285.4+/-17.8) mg/cm(3), respectively] (P<0.05, respectively), but no significant differences were evident in AP-SPINE or NECK BMD.

CONCLUSION

the femoral neck-derived volumetric BMD parameters using vQCT appeared better than the DXA-derived ones in discriminating osteoporotic postmenopausal women with vertebral fractures from those without. vQCT might be useful to evaluate the effect of osteoporotic vertebral fracture status on changes in bone mass in the femoral neck.

Prediction of proximal femur strength using a CT-based nonlinear finite element method: differences in predicted fracture load and site with changing load and boundary conditions

The annual occurrence of hip fracture due to osteoporosis as of 2002 had reached 120,000 in Japan. The increase has been very rapid. From a biomechanical perspective, hip fractures are thought to be caused in real settings by different directions of loading. Thus, clarification of the loading directions under which the proximal femur is most vulnerable to fracture would be helpful for elucidating fracture mechanics and establishing preventive interventions. The purpose of the current study was to clarify the influence of loading direction on strength and fracture site of the proximal femur using the CT-based nonlinear FE method to determine loading directions under which the proximal femur is most vulnerable to fracture. Contralateral femora were analyzed in 42 women with hip fracture (mean age, 82.4 years), comprising 20 neck fractures and 22 trochanteric fractures. Within 1 week after fracture, quantitative CT of the contralateral femur was performed in each patient and 3-dimensional FE models were created. One stance loading configuration (SC) and four different fall loading configurations (FC) were assigned. Nonlinear FE analysis was performed. Differences in fracture loads depending on differences in loading direction were analyzed and correlations among fracture loads in different loading directions were assessed. Next, fracture sites were also analyzed. Mean predicted fracture load in the SC was 3150 N. Mean fracture loads were 2270 N in FC1, 1060 N in FC2, 980 N in FC3, and 710 N in FC4. The correlation between predicted fracture loads in SC and those in each FC was significant with a correlation coefficient of 0.467-0.631. Predicted fracture sites in the SC appeared at the subcapital region in all patients and were categorized as neck fracture. However, trochanteric fractures occurred in all fall configurations except FC1. In FC1, a significant correlation was seen between real fracture type and predicted type. The current investigation could contribute to the acquisition of useful knowledge allowing the establishment of more efficacious means of preventing hip fractures.

Incidence of joint symptoms and bone fractures in Japanese postmenopausal breast cancer patients treated with adjuvant anastrozole

PURPOSE

Incidence of joint symptoms and bone fractures as well as changes in bone mineral density (BMD) in Japanese postmenopausal breast cancer patients treated with adjuvant anastrozole were investigated to determine whether there is an ethnic difference from Caucasian patients in the incidence of these adverse events of anastrozole.

METHODS

Adjuvant anastrozole was used to treat 348 postmenopausal breast cancer patients for a median period of 22 months. Adverse events of anastrozole including joint symptoms, loss of BMD, and bone fracture were investigated by means of chart review.

RESULTS

Joint symptoms developed in 96 (27.5%) patients. Age (younger than 65) and prior chemotherapy was strongly associated with an increased risk of joint symptoms. Annual fracture incidence was 0.86 and 0.85% and lumbar BMD decreased by 1.3 and 2.8% at 1 and 2 years, respectively. In comparison, the ATAC trial reported corresponding figures of 2.0 and 2.7 and of 2.2 and 4.0%.

CONCLUSION

Incidence and risk factors of joint symptoms are similar for Japanese and Caucasian patients, but the former tend to show a smaller decrease in BMD and a lower incidence of bone fractures, probably due to ethnic difference in the hormonal milieu.

Bone mineral density changes during the menopause transition in a multiethnic cohort of women

CONTEXT

Rates of bone loss across the menopause transition and factors associated with variation in menopausal bone loss are poorly understood.

OBJECTIVE

Our objective was to assess rates of bone loss at each stage of the transition and examine major factors that modify those rates.

DESIGN, SETTING, AND PARTICIPANTS

We conducted a longitudinal cohort study of 1902 African-American, Caucasian, Chinese, or Japanese women participating in The Study of Women's Health Across the Nation. Women were pre- or early perimenopausal at baseline.

OUTCOME MEASURE

We assessed bone mineral density (BMD) of the lumbar spine and total hip across a maximum of six annual visits.

RESULTS

There was little change in BMD during the pre- or early perimenopause. BMD declined substantially in the late perimenopause, with an average loss of 0.018 and 0.010 g/cm2.yr from the spine and hip, respectively (P<0.001 for both). In the postmenopause, rates of loss from the spine and hip were 0.022 and 0.013 g/cm2.yr, respectively (P<0.001 for both). During the late peri- and postmenopause, bone loss was approximately 35-55% slower in women in the top vs. the bottom tertile of body weight. Apparent ethnic differences in rates of spine bone loss were largely explained by differences in body weight.

CONCLUSIONS

Bone loss accelerates substantially in the late perimenopause and continues at a similar pace in the first postmenopausal years. Body weight is a major determinant of the rate of menopausal BMD loss, whereas ethnicity, per se, is not. Healthcare providers should consider this information when deciding when to screen women for osteoporosis.

Timing of peak bone mass: discrepancies between CT and DXA

CONTEXT

The time of life in which peak bone mass in the axial skeleton is attained has been the subject of considerable controversy, with estimates ranging from the time of sexual and skeletal maturity to the fifth decade of life.

OBJECTIVE

The objective was to examine whether dual energy x-ray absorptiometry (DXA) and computed tomography (CT) values for bone mass and bone density (BD) in the axial skeleton increase after sexual and skeletal maturity.

DESIGN/PARTICIPANTS

Measurements of vertebral bone mineral density and bone mineral content (BMC) by DXA and vertebral BD and BMC by CT were obtained in 50 sexually and skeletally mature white females at baseline and 3 yr later. CT BMC values were calculated through analysis of vertebral volume in relation to density (BMC = vertebral volume x BD).

RESULTS

Although neither CT BD nor BMC measures changed with time, DXA bone mineral density and BMC values were significantly higher at follow-up (P < 0.0001). Despite strong correlations between DXA and CT bone measures, DXA yielded greater changes in bone values in 47 of 50 subjects.

CONCLUSIONS

Bone acquisition in the lumbar spine as measured by CT reaches its peak by sexual and skeletal maturity. In contrast, bone values by DXA continue to increase after puberty and cessation of longitudinal growth. Increases in DXA measures are likely a reflection of inhomogeneous changes in soft tissues around the spine or of disproportionate increases in the posterior elements of the vertebrae rather than of changes within the vertebral body.

Prediction of strength and strain of the proximal femur by a CT-based finite element method

Hip fractures are the most serious complication of osteoporosis and have been recognized as a major public health problem. In elderly persons, hip fractures occur as a result of increased fragility of the proximal femur due to osteoporosis. It is essential to precisely quantify the strength of the proximal femur in order to estimate the fracture risk and plan preventive interventions. CT-based finite element analysis could possibly achieve precise assessment of the strength of the proximal femur. The purpose of this study was to create a simulation model that could accurately predict the strength and surface strains of the proximal femur using a CT-based finite element method and to verify the accuracy of our model by load testing using fresh frozen cadaver specimens. Eleven right femora were collected. The axial CT scans of the proximal femora were obtained with a calibration phantom, from which the 3D finite element models were constructed. Materially nonlinear finite element analyses were performed. The yield and fracture loads were calculated, while the sites where elements failed and the distributions of the principal strains were determined. The strain gauges were attached to the proximal femoral surfaces. A quasi-static compression test of each femur was conducted. The yield loads, fracture loads and principal strains of the prediction significantly correlated with those measured (r=0.941, 0.979, 0.963). Finite element analysis showed that the solid elements and shell elements in undergoing compressive failure were at the same subcapital region as the experimental fracture site.

Quantitative computed tomography BMD reference values in women of Izmir, Turkey

In quantitative computed tomography applications for the diagnosis of osteoporosis, the bone mineral density value obtained has to be compared with a reference data. This data is influenced by several factors including sex, age, and ethnicity. Therefore, reference data that accurately represent the population at large is essential. We established age-based quantitative computed tomography bone mineral density reference values for healthy women residing in Izmir, Turkey. We recruited 396 healthy women from 20 to 83 years old (mean age, 51.08 years). Quantitative computed tomography bone mineral density measurements were performed using the GE 9800 Highlight Advantage scanner at the L1, L2, and L3 lumbar vertebrae. The mean bone mineral density (mg/cm) +/- standard deviation of the normal reference group of women from 20 to 39 years old was 168.86 mmg/cm3 +/- 21.59. The threshold bone mineral density value for osteoporosis at a T score < -2.5 was 114.83 mg/cm3. The slope, intercept, and r values at bone mineral density versus age linear regression test were -2.44, 251.1, and 0.70, respectively. The percentage of annual bone mineral density loss was 1.6%. The bone mineral density values of Turkish women were not distinct from most countries' reference values.

LEVEL OF EVIDENCE

Diagnostic study, Level II (Development of diagnostic criteria on consecutive patients [with universally applied reference "gold" standard]). See the Guidelines for Authors for a complete description of the levels of evidence.

Differences in hip quantitative computed tomography (QCT) measurements of bone mineral density and bone strength between glucocorticoid-treated and glucocorticoid-naive postmenopausal women

Chronic treatment with glucocorticoids (GCs) leads to significant bone loss and increased risk of fractures. In chronically GC-treated patients, hip fracture risk is nearly 50%. The purpose of this investigation was to determine if there are differences in the quantities of trabecular and cortical bone and bone strength of the hip between GC-treated osteoporotic patients and controls.

METHODS

Study subjects were GC-treated osteoporotic postmenopausal women, and controls were postmenopausal women, recruited for separate clinical trials. Quantitative computed tomography (QCT) and dual-energy X-ray absorptiometry (DXA) of the hip were obtained from all subjects. QCT outcome variables measured included total, cortical, and trabecular BMD of hip subregions (femoral neck and trochanter) and total hip. In addition, finite element modeling (FEM) was performed on a subset of 19 cases and 38 controls, matched on age (+/- 5 years), weight (+/- 5 kg), and history of hormone replacement (> 1 year use) to assess failure load in stance and fall loading conditions. Generalized linear models were used to adjust the QCT variables for covariates between groups. Multiple regression was performed to identify independent predictors of bone strength from the QCT variables.

RESULTS

Compared with controls, GC-treated subjects were significantly (p < 0.05) younger, weighed less, and had more years of hormone replacement. QCT of the hip in GC-treated subjects for total femoral integral, cortical, and trabecular BMD averaged 4.9-23.2% (p < 0.002) less than controls, and similar results were seen by hip subregion including the trochanter and femoral neck. DXA of the total hip was 17% lower in GC subjects than controls (p < 0.05). Compared with controls, FEM failure load in GC subjects was 15% (p<0.05) and 16% (p = 0.07) lower for stance and fall loading conditions, respectively. Multiple regression analysis demonstrated that a combination of QCT measures was correlated with bone strength as measured by FEM.

CONCLUSIONS

Chronic GC treatment in postmenopausal women resulted in significantly decreased BMD of the hip, measured by QCT, with loss of both trabecular and cortical bone. In addition, GC treatment decreased bone strength as determined by FEM. The reduced cortical and trabecular bone mass in the hip may contribute to the disproportionately high hip fracture rates observed in GC-treated subjects.

Osteoporosis and fracture risk in women of different ethnic groups

Osteoporosis and 1-year fracture risk were studied in 197,848 postmenopausal American women from five ethnic groups. Weight explained differences in BMD, except among blacks, who had the highest BMD. One SD decrease in BMD predicted a 50% increased fracture risk in each group. Despite similar relative risks, absolute fracture rates differed.

INTRODUCTION

Most information about osteoporosis comes from studies of white women. This study describes the frequency of osteoporosis and the association between BMD and fracture in women from five ethnic groups.

MATERIALS AND METHODS

This study was made up of a cohort of 197,848 community-dwelling postmenopausal women (7784 blacks, 1912 Asians, 6973 Hispanics, and 1708 Native Americans) from the United States, without known osteoporosis or a recent BMD test. Heel, forearm, or finger BMD was measured, and risk factor information was obtained; 82% were followed for 1 year for new fractures. BMD and fracture rates were compared, adjusting for differences in covariates.

RESULTS

By age 80, more than one-fifth of women in each ethnic group had peripheral BMD T scores <-2.5. Black women had the highest BMD; Asian women had the lowest. Only the BMD differences for blacks were not explained by differences in weight. After 1 year, 2414 new fractures of the spine, hip, forearm, wrist, or rib were reported. BMD at each site predicted fractures equally well within each ethnic group. After adjusting for BMD, weight, and other covariates, white and Hispanic women had the highest risk for fracture (relative risk [RR] 1.0 [referent group] and 0.95, 95% CI, 0.76, 1.20, respectively), followed by Native Americans (RR, 0.87; 95% CI, 0.57, 1.32), blacks (RR, 0.52; 95% CI, 0.38, 0.70), and Asian Americans (RR, 0.32; 95% CI, 0.15, 0.66). In age- and weight-adjusted models, each SD decrease in peripheral BMD predicted a 1.54 times increased risk of fracture in each ethnic group (95% CI, 1.48-1.61). Excluding wrist fractures, the most common fracture, did not materially change associations.

CONCLUSIONS

Ethnic differences in BMD are strongly influenced by body weight; fracture risk is strongly influenced by BMD in each group. Ethnic differences in absolute fracture risk remain, which may warrant ethnic-specific clinical recommendations.

Standardized Data and Relationship between Bone Growth and Bone Metabolism in Female Goettingen Minipigs

Minipigs have been studied as a model of osteoporosis. However, little information is available regarding their bone physiology. We established standardized bone data and investigated the relationship between bone growth and bone metabolism in female minipigs. Blood and urine samples were obtained from 53 female Göttingen minipigs, 3-76 months of age, for measurement of bone biomarkers (i.e., BAP, OC, NTX, and DPD). The lumbar vertebra and femur were excised to determine the growth plate condition, bone length, bone mineral content (BMC), and bone mineral density (BMD). High levels of bone biomarkers were observed during the initial period after birth, decreasing thereafter with age. Bone biomarkers were confirmed to be highly correlated with age (R(2) > 0.7). The growth plates of the lumbar vertebra and the femur began to close at 21 and 25 months of age, respectively, and closed completely at 42 months of age. Bone length increased rapidly before growth plate closure, and reached a peak at 21 and 28 months of age in the lumbar vertebra and the femur, respectively. The levels of BMC and BMD increased rapidly before growth plate closure, and continued to increase slowly until 76 months of age. A high negative correlation (-0.855 < r < -0.711, p<0.001) was confirmed between the bone biomarkers and the bone measurement data. These results indicate that the bone turnover velocity is consistent with the bone growth velocity in female Göttingen minipigs.

Ethnic variation in bone density in premenopausal and early perimenopausal women: effects of anthropometric and lifestyle factors

Bone mineral density (BMD) and fracture rates vary among women of differing ethnicities. Most reports suggest that BMD is highest in African-Americans, lowest in Asians, and intermediate in Caucasians, yet Asians have lower fracture rates than Caucasians. To assess the contributions of anthropometric and lifestyle characteristics to ethnic differences in BMD, we assessed lumbar spine and femoral neck BMD by dual-energy x-ray absorptiometry in 2277 (for the lumbar spine) and 2330 (for the femoral neck) premenopausal or early perimenopausal women (mean age, 46.2 yr) participating in the Study of Women's Health Across the Nation. Forty-nine percent of the women were Caucasian, 28% were African-American, 12% were Japanese, and 11% were Chinese. BMDs were compared among ethnic groups before and after adjustment for covariates. Before adjustment, lumbar spine and femoral neck BMDs were highest in African-American women, next highest in Caucasian women, and lowest in Chinese and Japanese women. Unadjusted lumbar spine and femoral neck BMDs were 7-12% and 14-24% higher, respectively, in African-American women than in Caucasians, Japanese, or Chinese women. After adjustment, lumbar spine and femoral neck BMD remained highest in African-American women, and there were no significant differences between the remaining groups. When BMD was assessed in a subset of women weighing less than 70 kg and then adjusted for covariates, lumbar spine BMD became similar in African-American, Chinese, and Japanese women and was lowest in Caucasian women. Adjustment for bone size increased values for Chinese women to levels equal to or above those of Caucasian and Japanese women. Among women of comparable weights, there are no differences in lumbar spine BMD among African-American, Chinese, and Japanese women, all of whom have higher BMDs than Caucasians. Femoral neck BMD is highest in African-Americans and similar in Chinese, Japanese, and Caucasians. These findings may explain why Caucasian women have higher fracture rates than African-Americans and Asians.

Lactose Maldigestion, Calcium Intake and Osteoporosis in African-, Asian-, and Hispanic-Americans

Dietary calcium is critical for the development of the human skeleton and likely plays an important role in the prevention of osteoporosis. Dairy products provide approximately three-fourths of calcium consumed in the diet and are the most concentrated sources of this essential nutrient. One obstacle that likely interferes with calcium consumption among many ethnic groups is lactose maldigestion. The real or perceived occurrence of intolerance symptoms after dairy food consumption may cause maldigesters to avoid dairy products. Several investigators have observed a relationship between lactose maldigestion, dietary calcium and osteoporosis in Caucasian populations. Research on ethnically diverse populations is necessary to better understand how lactose maldigestion influences the risk for osteoporosis. Low calcium intakes, a greater than previously thought potential for low bone density and extensive lactose maldigestion among Hispanic-American and Asian-American populations may create an elevated risk for osteoporosis. Dietary management strategies for lactose maldigesters to increase calcium consumption include consuming (1) dairy foods with meals, (2) yogurts, (3) calcium-fortified foods, (4) using lactose digestive aids and (5) including dairy foods daily in the diet to enhance colonic metabolism of lactose.

Effects of aging on bone mineral content and bone biomarkers in female cynomolgus monkeys

Age-related changes in bone mineral content and bone biomarkers were assessed over the complete lifespan of female cynomolgus monkeys. The bone mass of the lumbar spine increased linearly from birth to about 2.5 years of age, and this increase gradually slowed thereafter until a peak bone mass was achieved at 9 years of age. The bone mass stabilized after 9 years of age, showing no sign of further reduction with age. In contrast with the significant increase in bone mass before 2.5 years of age, significant decreases occurred in the serum concentrations of the following bone formation markers: intact osteocalcin, bone-specific alkaline phosphatase and amino-terminal propeptide of type I procollagen, but the serum concentration of carboxy-terminal propeptide of type I procollagen did not change significantly throughout the entire lifespan. Concerning the bone resorption markers, the levels of tartrate-resistant acid phosphatase fluctuated throughout the entire lifespan. The skeleton of an aging female monkey undergoes changes similar to those observed in senescent humans, but did not undergo the menopausal changes seen in women. The use of female cynomolgus monkeys to model human skeletal interventions should therefore be undertaken with consideration of the similarities and differences between cynomolgus monkeys and humans.