Physical activity increases bone size in prepubertal boys and bone mass in prepubertal girls: a combined cross-sectional and 3-year longitudinal study

This study evaluates the effect on the skeleton of physical activity from age 9 to 16. In 42 girls and 44 boys, bone mass and bone size were evaluated longitudinally by dual-energy X-ray absorptiometry (DXA) from ages 13 to 16. Physical activity from ages 9 to 13 was cross-sectionally evaluated at baseline (age 13). Girls with high physical activity from ages 9 to 13 at baseline had higher femoral neck bone mineral content (FN BMC; g) (P = 0.07), higher FN areal bone mineral density (FN aBMD; g/cm2), and higher FN volumetric BMD (FN vBMD; g/cm3) (both P < 0.05) compared with girls of low activity. FN width (cm) and head aBMD (an unloaded region) showed no differences when comparing the two groups. Three years of further high and low activity (from ages 13 to 16) did not yield any increased differences between the two groups. Boys with high physical activity from ages 9 to 13, had at baseline higher FN BMC, FN aBMD, and FN width (all P < 0.05) compared with boys with low activity. FN vBMD and head aBMD showed no differences when comparing the two groups. Three years of further high and low activity did not yield any increased differences between the two groups. We conclude that exercise may yield skeletal benefits before age 13, and that 3 years of continued high or low level activity up to age 16 did not yield any increased differences in bone size or bone mass in either girls or boys.     

Rural versus nonrural differences in BMC, volumetric BMD, and bone size: a population-based cross-sectional study

Despite reports of lower fracture risk among rural versus urban populations, few studies have investigated rural versus urban differences in bone mineral content (BMC) and bone mineral density (BMD). Population differences in cross-sectional bone geometry and understanding lifestyle factors responsible for these differences may reveal insights into the reason for differences in fracture risk. We hypothesized that if lifestyle differences in bone mass, size, and geometry are a result of muscle strength, activity, or dietary differences, Hutterite and rural populations should have greater bone mass compared to nonrural populations. The study population consisted of 1189 individuals: 504 rural Hutterites (188 men), 349 rural individuals (>75% life farming, 184 men), and 336 nonrural individuals (never lived on farm, 134 men) aged 20 to 66 years. BMC, bone area, and areal BMD (aBMD) of the total body (TB), hip, femoral neck (FN), and spine by DXA; volumetric BMD (vBMD) and bone geometry at the 4% and 20% radius; polar stress strain index (pSSI), a measure of bone strength, at the 20% pQCT site; and strength, 7-day activity recall, and 24-h diet recall were collected and compared among groups. Hutterite women and men had greater grip strength compared to rural and nonrural populations (both, P < 0.001). Rural women had greater activity versus Hutterite and nonrural (P < 0.001), while both Hutterite and rural men had greater activity than nonrural (P < 0.001). Hutterite and rural populations tended to have greater BMC and areal size than the nonrural population, while Hutterites had greater BMC and areal size than rural population at some (TB, FN for females only), but not all (proximal hip), sites. Cortical vBMD was inversely associated with periosteal circumference at the 20% radius in women (r = −0.25, P < 0.001) and men (r = −0.28, P < 0.001) and was higher in nonrural versus Hutterite and rural men. Hutterite and rural women and men had greater pSSI at the 20% radius compared to nonrural; inclusion of strength measurements explained population differences among women, but not men. Lifestyle differences did not explain population differences in BMC, aBMD, vBMD, or bone size.     

体积骨密度的估算方法及其对诊断骨质疏松的意义

骨密度（BMD）有面积骨密度（aBMD）和体积骨密度（vBMD）两种表达方式,它们在临床实验研究中被广泛采用。本文综述了vBMD的估算方法、aBMD和vBMD存在的性别差异和种族差异,以及aBMD和vBMD对诊断骨质疏松的影响。     

Frame size, ethnicity, lifestyle, and biologic contributors to areal and volumetric lumbar spine bone mineral density in Indian/Pakistani and American Caucasian premenopausal women.

Published data on the spinal bone mineral density (BMD) of premenopausal women originating from the Indian subcontinent (Indian/Pakistani) are few. We compared anteroposterior (AP) and lateral areal BMD (aBMD) using dual X-ray absorptiometry and calculated volumetric BMD (vBMD) in Indian/Pakistani (n = 47) vs American (n = 47) women with dissimilar statures and skeletal sizes. To account for differences, we "adjusted" lumbar aBMD separately for vertebral size (aBMD/the square root of the projected area), height (aBMD/height), and hip skeletal width (aBMD/hip width). We "corrected" bone mineral content (BMC), aBMD, and vBMD for frame size, collectively using height, hip width, and vertebral size. Unadjusted mean aBMD values for AP lumbar (L1-L4, p = 0.0086; L3-L4, p = 0.044) spine were higher in Americans than Indians/Pakistanis,whereas lateral vBMD (p = 0.56) or aBMD (p = 0.060) values were not different. After adjusting for height, hip width, or vertebral size, or correcting for frame size, differences in aBMD disappeared. Regression analyses indicated that the best measures to correct for frame size were: vertebral area for BMC, hip width for aBMD, and vertebral width for lateral vBMD. Height was not significant in any model. In correcting for frame size, we accounted for 73-85% of the variability in BMC, 22-28% in aBMD, and 27% in lateral vBMD. After frame size was corrected, we accounted for 34% of the variability in AP BMC and aBMD, in contrast with 6-9% in the lateral models. Five significant biologic and lifestyle factors remained in AP models; only body weight remained for lateral spine. Upon accounting for frame size using regression, much variability in BMD, aBMD, and vBMD was explained by lifestyle and biologic factors, not by ethnicity.     

Relationship of femoral neck areal bone mineral density to volumetric bone mineral density, bone size, and femoral strength in men and women

Summary

Using combined dual-energy X-ray absorptiometry (DXA) and quantitative computed tomography, we demonstrate that men matched with women for femoral neck (FN) areal bone mineral density (aBMD) have lower volumetric BMD (vBMD), higher bone cross-sectional area, and relatively similar values for finite element (FE)-derived bone strength.

Introduction

aBMD by DXA is widely used to identify patients at risk for osteoporotic fractures. aBMD is influenced by bone size (i.e., matched for vBMD, larger bones have higher aBMD), and increasing evidence indicates that absolute aBMD predicts a similar risk of fracture in men and women. Thus, we sought to define the relationships between FN aBMD (assessed by DXA) and vBMD, bone size, and FE-derived femoral strength obtained from quantitative computed tomography scans in men versus women.

Methods

We studied men and women aged 40 to 90?years and not on osteoporosis medications.

Results

In 114 men and 114 women matched for FN aBMD, FN total cross-sectional area was 38% higher (P?P?Conclusions In this cohort of young and old men and women from Rochester, MN, USA who are matched by FN aBMD, because of the offsetting effects of bone size and vBMD, femoral strength and the load-to-strength ratio tended to be relatively similar across the sexes.     

Gender differences in bone density at different skeletal sites of acquisition with age in Chinese children and adolescents

Bone mass acquisition from different genders and races of children and adolescents may vary. To explore gender- and age-related differences in bone mineral density (BMD) measurements in Chinese children and adolescents, we used the dual-energy X-ray absorptiometry (DXA) bone densitometer to take BMD measurements at the posteroanterior (PA) and lateral spine, hip, and forearm in 1286 healthy children and adolescents, ranging from 6 to 24 years of age. Our results show a correlation between BMD measurements taken from different skeletal sites and from different ages of subjects. Male data were best fit to a power regression model, yielding the largest determinant coefficients (R ²), whereas S regression was the best fitting model for females. In individuals younger than 17 years of age, the rate of BMD accumulation in the PA spine is more rapid in females than in males, whereas in individuals older than 19 years of age, the converse was found to be true. In children younger than 14 years of age, BMD measurements, taken from the lateral spine, the neck and trochanter of the femur, and the total hip, correlated with age similarly in both genders. Additionally, in measurements taken from the forearm ultradistal and 1/3 region, BMD measurements from similar ages of both genders are similar. With increasing age, BMD measurements in males become significantly higher than those of females. However, volumetric BMD (vBMD) measurements from both genders show good uniformity at the lateral spine with a near overlap of the two models. Our findings suggest that vBMD acquisition measurements in Chinese children and adolescents show no gender differences, with gender differences only demonstrated in areal BMD (aBMD) measurements taken from different skeletal sites.     

The association of bone mineral density measures with incident cardiovascular disease in older adults

Summary The associations of volumetric and areal bone mineral density (BMD) measures with incident cardiovascular disease (CVD) were studied in a biracial cohort of 2,310 older adults. BMD measures were inversely related to CVD in women and white men, independent of age and shared risk factors for osteoporosis and CVD. Introduction We investigated the associations of volumetric (vBMD) and areal (aBMD) bone mineral density measures with incident cardiovascular disease (CVD) in older adults enrolled in the Health, Aging, and Body Composition study. Methods The incidence of CVD was ascertained in 2,310 well-functioning white and black participants (42% black; 55% women), aged 68–80 years. aBMD measures of the hip were assessed using DXA. Spine trabecular, integral, and cortical vBMD measures were obtained using QCT. Results During an average follow-up of 5.4 years, 23% of men and 14% of women had incident CVD. Spine vBMD measures were inversely associated with incident CVD in white men [HR(integral)=1.39, 95% CI 1.03–1.87; HR(cortical)=1.38, 95% CI 1.03–1.84], but not in black men. In women, aBMD measures of the total hip (HR = 1.36, 95% CI 1.03–1.78), femoral neck (HR = 1.44, 95% CI 1.10–1.90), and trochanter (HR = 1.34, 95% CI 1.04–1.72) exhibited significant associations with CVD in blacks, but not in whites. All associations were independent of age and shared risk factors between osteoporosis and CVD, and were not explained by inflammatory cytokines or oxidized LDL. Conclusion Our results provide support for an inverse association between BMD and incident CVD. Further research should elucidate possible pathophysiological mechanisms linking osteoporosis and CVD.     

Effects of genes, sex, age, and activity on BMC, bone size, and areal and volumetric BMD.

Quantitative genetic analyses of bone data for 710 inter-related individuals 8-85 yr of age found high heritability estimates for BMC, bone area, and areal and volumetric BMD that varied across bone sites. Activity levels, especially time in moderate plus vigorous activity, had notable effects on bone. In some cases, these effects were age and sex specific. INTRODUCTION: Genetic and environmental factors play a complex role in determining BMC, bone size, and BMD. This study assessed the heritability of bone measures; characterized the effects of age, sex, and physical activity on bone; and tested for age- and sex-specific bone effects of activity. MATERIALS AND METHODS: Measures of bone size and areal and volumetric density (aBMD and vBMD, respectively) were obtained by DXA and pQCT on 710 related individuals (466 women) 8-85 yr of age. Measures of activity included percent time in moderate + vigorous activity (%ModVig), stair flights climbed per day, and miles walked per day. Quantitative genetic analyses were conducted to model the effects of activity and covariates on bone outcomes. RESULTS: Accounting for effects of age, sex, and activity levels, genes explained 40-62% of the residual variation in BMC and BMD and 27-75% in bone size (all p<0.001). Decline in femoral neck (FN), hip, and spine aBMD with advancing age was greater among women than men (age-by-sex interaction; all p 相似文献   

女性年龄相关的腰椎骨量与骨骼大小的关系及对诊断骨质疏松的影响

目的探讨腰椎骨量(面积骨密度和体积骨密度)与年龄和骨骼骨面积(BA)大小之间的关系,及腰椎骨骼大小对评价骨量和诊断骨质疏松(OP)的影响。方法采用QDR-4500A型扇形束双能X线吸收法骨密度仪,测量5585例年龄5～96岁的女性正位腰椎BA、骨矿含量(BMC)、面积骨密度(aBMD)及估算体积骨密度(vBMD)。结果腰椎aBMD和vBMD的峰值BMD(x珋±s)分别为0.9884±0.1064g/cm2和0.1310±0.0128g/cm3。在所有年龄阶段aBMD随年龄的变化率显著大于vBMD。腰椎BA与BMC、aBMD和vBMD均呈显著正相关,其中BA与BMC的相关系数最大(r=0.706,P=0.000),与aBMD的相关系数次之(r=0.394,P=0.000),与vBMD的相关系数最小(r=0.141,P=0.000)。年龄≥40岁(平均52.7±9.58岁)的受试者(n=4012)腰椎BA按四分位数分成Q1、Q2、Q3和Q4组,4个组之间的BA、BMC和aBMD的平均值均有显著性差异。采用aBMD诊断OP,4个组的OP检出率分别为Q1=33.6%、Q2=17.9%、Q3=13.3%和Q4=8.39%,呈显著性梯次降低;与总体组比较,Q1组的患病风险增加126%,Q2、Q3和Q4组的患病风险分别降低3%、31%和59%。采用vBMD诊断OP,4个组的OP检出率分别为Q1=27.4%、Q2=18.3%、Q3=15.9%和Q4=14.0%,其梯次差异显著低于aBMD;与总体组比较,Q1组的患病风险增加62%,Q2、Q3和Q4组的患病风险分别降低4%、19%和30%。Q1组aBMD的OP检出率显著高于vBMD,Q4组aBMD的OP检出率显著低于vBMD。在椎体最小的Q1组,aBMD(OR=2.26)的患病风险比vBMD(OR=1.62)大约高64%,在椎体最大的Q4组,aBMD(OR=0.41)的患病风险比vBMD(OR=0.70)大约低29%。结论该研究揭示腰椎vBMD并不能完全消除骨骼大小对评价骨量和诊断OP的影响。在腰椎椎体较小的受试者,aBMD诊断OP的敏感性高于vBMD;在椎体较大的受试者,vBMD诊断OP的敏感性则高于aBMD。     

Catch up in bone acquisition in young adult men with late normal puberty

The aim of this study was to investigate the development of bone mineral density (BMD) and bone mineral content (BMC) in relation to peak height velocity (PHV), and to investigate whether late normal puberty was associated with remaining low BMD and BMC in early adulthood in men. In total, 501 men (mean ± SD, 18.9 ± 0.5 years of age at baseline) were included in this 5‐year longitudinal study. Areal BMD (aBMD) and BMC, volumetric BMD (vBMD) and cortical bone size were measured using dual‐energy X‐ray absorptiometry (DXA) and pQCT. Detailed growth and weight charts were used to calculate age at PHV, an objective assessment of pubertal timing. Age at PHV was a strong positive predictor of the increase in aBMD and BMC of the total body (R² aBMD 11.7%; BMC 4.3%), radius (R² aBMD 23.5%; BMC 22.3%), and lumbar spine (R² aBMD 11.9%; BMC 10.5%) between 19 and 24 years (p < 0.001). Subjects were divided into three groups according to age at PHV (early, middle, and late). Men with late puberty gained markedly more in aBMD and BMC at the total body, radius, and lumbar spine, and lost less at the femoral neck (p < 0.001) than men with early puberty. At age 24 years, no significant differences in aBMD or BMC of the lumbar spine, femoral neck, or total body were observed, whereas a deficit of 4.2% in radius aBMD, but not in BMC, was seen for men with late versus early puberty (p < 0.001). pQCT measurements of the radius at follow‐up demonstrated no significant differences in bone size, whereas cortical and trabecular vBMD were 0.7% (p < 0.001) and 4.8% (p < 0.05) lower in men with late versus early puberty. In conclusion, our results demonstrate that late puberty in males was associated with a substantial catch up in aBMD and BMC in young adulthood, leaving no deficits of the lumbar spine, femoral neck, or total body at age 24 years. © 2012 American Society for Bone and Mineral Research.     

Vertebral Size,Bone Density,and Strength in Men and Women Matched for Age and Areal Spine BMD

To explore the possible mechanisms underlying sex‐specific differences in skeletal fragility that may be obscured by two‐dimensional areal bone mineral density (aBMD) measures, we compared quantitative computed tomography (QCT)‐based vertebral bone measures among pairs of men and women from the Framingham Heart Study Multidetector Computed Tomography Study who were matched for age and spine aBMD. Measurements included vertebral body cross‐sectional area (CSA, cm²), trabecular volumetric BMD (Tb.vBMD, g/cm³), integral volumetric BMD (Int.vBMD, g/cm³), estimated vertebral compressive loading and strength (Newtons) at L₃, the factor‐of‐risk (load‐to‐strength ratio), and vertebral fracture prevalence. We identified 981 male‐female pairs (1:1 matching) matched on age (± 1 year) and QCT‐derived aBMD of L₃ (± 1%), with an average age of 51 years (range 34 to 81 years). Matched for aBMD and age, men had 20% larger vertebral CSA, lower Int.vBMD (–8%) and Tb.vBMD (–9%), 10% greater vertebral compressive strength, 24% greater vertebral compressive loading, and 12% greater factor‐of‐risk than women (p < 0.0001 for all), as well as higher prevalence of vertebral fracture. After adjusting for height and weight, the differences in CSA and volumetric bone mineral density (vBMD) between men and women were attenuated but remained significant, whereas compressive strength was no longer different. In conclusion, vertebral size, morphology, and density differ significantly between men and women matched for age and spine aBMD, suggesting that men and women attain the same aBMD by different mechanisms. These results provide novel information regarding sex‐specific differences in mechanisms that underlie vertebral fragility. © 2014 American Society for Bone and Mineral Research.     

Measurement of subregional vertebral bone mineral density in vitro using lateral projection dual-energy X-ray absorptiometry: validation with peripheral quantitative computed tomography

Although a strong relationship exists between areal bone mineral density (aBMD) derived from dual-energy X-ray absorptiometry (DXA) and bone strength, the predictive validity of aBMD for osteoporotic vertebral fractures remains suboptimal. The diagnostic sensitivity of DXA may be improved by assessing aBMD within vertebral subregions, rather than relying on an estimate derived from the total area of the vertebra. The objective of this study was to validate a method of measuring subregional vertebral aBMD in vitro using lateral-projection DXA against subregional volumetric BMD (vBMD) measured with peripheral quantitative computed tomography (pQCT). A mixed set of 49 lumbar and thoracic vertebrae from 25 donors were scanned using lateral-projection DXA and pQCT. aBMD and apparent vBMD were measured in 7 vertebral regions (1 total area and 6 subregions) from the lateral DXA scan. vBMD was calculated in anatomically equivalent regions from pQCT scan data, using a customised software program designed to increase efficiency of the analysis process. Significant differences in densitometric parameters between subregions were observed by DXA and pQCT (P < 0.01). Subregional vBMD derived from pQCT was explained by a significant proportion of the variance in DXA-derived aBMD (R ² = 0.51–0.67, P < 0.05) and apparent vBMD (R ² = 0.64–0.75, P < 0.05). These results confirm the validity of measuring aBMD in vertebral subregions using lateral-projection DXA. The clinical significance should now be explored.     

Increased Trabecular Volumetric Bone Mass Density in Familial Hypocalciuric Hypercalcemia (FHH) Type 1: A Cross-Sectional Study

Familial Hypocalciuric Hypercalcaemia (FHH) Type 1 is caused by an inactivating mutation in the calcium-sensing receptor (CASR) gene resulting in elevated plasma calcium levels. We investigated whether FHH is associated with change in bone density and structure. We compared 50 FHH patients with age- and gender-matched population-based controls (mean age 56 years, 69 % females). We assessed areal BMD (aBMD) by DXA-scans and total, cortical, and trabecular volumetric BMD (vBMD) as well as bone geometry by quantitative computed tomography (QCT) and High-Resolution peripheral-QCT (HR-pQCT). Compared with controls, FHH females had a higher total and trabecular hip vBMD and a lower cortical vBMD and hip bone volume. Areal BMD and HRpQCT indices did not differ except an increased trabecular thickness and an increased vBMD at the transition zone between cancellous and cortical bone in of the tibia in FHH. Finite element analyses showed no differences in bone strength. Multiple regression analyses revealed correlations between vBMD and P-Ca²⁺ levels but not with P-PTH. Overall, bone health does not seem to be impaired in patients with FHH. In FHH females, bone volume is decreased, with a lower trabecular volume but a higher vBMD, whereas cortical vBMD is decreased in the hip. This may be due to either an impaired endosteal resorption or corticalization of trabecular bone. The smaller total bone volume suggests an impaired periosteal accrual, but bone strength is not impaired. The findings of more pronounced changes in females may suggest an interaction between sex hormones and the activity of the CaSR on bone.     

Peripubertal Moderate Exercise Increases Bone Mass in Boys but Not in Girls: A Population-Based Intervention Study

On the basis of cross-sectional studies in elite athletes and longitudinal studies, physical activity in growing children has been suggested to enhance bone mineral acquisition and prevent osteoporosis later in life. The level of exercise in most of these studies is not applicable in a population on a day-to-day basis. The aim of this study was to determine whether moderate increased exercise within the school curriculum from age 12 to 16 years would have anabolic bone effects. In a population-based setting of 40 boys and 40 girls the school curriculum was enhanced to physical education 4 times per week for 3–4 years. Controls were 82 boys and 66 girls who had had physical education twice a week over a corresponding period. Both cases and controls were measured at age 16 years. Bone mineral content (BMC), areal bone mineral density (aBMD), bone size (femoral neck width) and volumetric BMD (vBMD) were measured in total body, spine and femoral neck (FN) by dual-energy X-ray absorptiometry. Data are presented as mean ± SD. BMC (8 ± 15%, p= 0.04), aBMD (9 ± 13%, p= 0.002) and vBMD (9 ± 15%, p= 0.001) were all higher in FN in the male intervention group compared with controls. FN bone size was no higher in the intervention group than in the controls. In girls, no differences were found when comparing the intervention group with controls. The results remained after adjusting for confounding factors such as weight, height, milk intake and activity after school. In summary, we report that increased bone mass can be achieved in a population-based cohort of boys (but not in girls) by moderate increased physical activity within the school curriculum from age 12 to 16 years. We speculate that the same results can be seen in girls if intervention starts at an earlier age. We conclude that increasing the physical education content of the Swedish school curriculum may improve bone mass in at least peripubertal boys. Received: 20 April 2000 / Accepted: 17 October 2000     

Monitoring Bone Growth Using Quantitative Ultrasound in Comparison with DXA and pQCT

Quantitative ultrasound (QUS) is a safe, inexpensive, and nonradiation method for bone density assessment. QUS correlates with, and predicts fragility fractures comparable to, dual-energy X-ray absorptiometry (DXA)-derived bone mineral density (BMD) in postmenopausal women. However, its validity in monitoring bone growth in children is not well understood. Two hundred and fifty-eight 10–13 yr pubertal girls and 9 37–43 yr adults without diseases or history of medications known to affect bone metabolism were included in the 2-yr prospective study. Calcaneal broadband ultrasound attenuation (cBUA) was assessed using QUS-2 (Quidel, Santa Clara, CA), speed of sound of tibial shaft (tSOS) using Omnisense (Sunlight Technologies, Israel), apparent volumetric BMD (vBMD) of tibial shaft using peripheral quantitative computed tomography (pQCT; XCT2000, Stratec), and femoral neck (FN) and lumbar spine 2–4 (LS) areal BMD (aBMD) using DXA (Prodigy, GE). Over the 2 yr in girls, FN and LS aBMD showed the largest increases (17 ± 8% and 20 ± 8%, respectively), followed by tibial vBMD and cBUA (10 ± 5% and 9 ± 9%, respectively). There was no apparent change in tSOS (2 ± 3%). The increase in FN and LS aBMD attenuated 48% and 40%, respectively, after adjustment of the change in body size. The change of cBUA correlated significantly with change in tibial vBMD and FN and LS aBMD (r = 0.24–0.40). At the matched location, tSOS correlated only with cortical vBMD, not with cortical thickness, apparent vBMD, or bone size. The long-term reproducibility, assessed using the concordance correlation coefficient of young adults' pre-post measurements, was substantially lower in tSOS than cBUA, tibial vBMD, FN, and LS aBMD (0.65 vs 0.97, 0.95, 0.98, and 0.96; p < 0.05). The transverse transmission method-derived calcaneal BUA, but not the axial transmission method-derived SOS, is comparable to DXA and pQCT for monitoring bone densitometric change in pubertal girls. The role of QUS in fracture-risk prediction in children and adolescents needs further investigation.     

The association of pregnancy history with areal and volumetric bone mineral density in adolescence

Introduction Studies demonstrate that pregnancy may interfere with bone mineral density. Adolescence is a crucial time of life for bone mass acquisition and there are some questions as to the influence of pregnancy on bone mass at this age. Objective To evaluate the association between pregnancy history and areal (BMD) and volumetric (vBMD) bone mineral density in adolescence. Subjects and methods A cross-sectional study of 119 adolescents ranging from 12–20 years of age was conducted; 30 of these girls had a history of full-term pregnancy. The adolescents were selected during a routine visit to the Adolescent Gynecology Outpatient Facility, completed a questionnaire, and had a physical examination to evaluate weight, height and Tanner stage. Bone mineral densitometry of the lumbar spine (L₁–L₄) and total body (TB) was performed to measure bone mineral density and body composition. Results The mean measurements of the area, bone mineral content (BMC), BMD and vBMD of L₁–L₄ and the area, BMC and BMD of TB were not significantly different between adolescents with and without a pregnancy history, stratified by chronologic and gynecologic age. The percentage of adolescents with altered Z-scores was similar in both groups, and the prevalence ratio showed no association between pregnancy history and low bone mass (PR=0.52; CI 0.04–6.07). Upon multiple regression analysis, body mass index (BMI) and lean body mass (LBM) were the main factors associated with lumbar spine and total body measurements. Pregnancy history was inversely associated with areal BMD of L₁–L₄ (R ²=0.04) and vBMD of L₁–L₄ (R ²=0.04), accounting for only 4% variation in the lumbar spine. Conclusion These data suggest that adolescent pregnancy seems to exert no significant influence on the acquisition of bone mass and does not appear to represent a risk factor for osteoporosis in the future.     

Reproducibility of Volume-Adjusted Bone Mineral Density of Spine and Hip from Dual X-ray Absorptiometry

Skeletal size has a confounding effect on areal bone mineral density (aBMD) related to differences in skeletal volume. Several methods have been proposed for calculating volumetric BMD (vBMD), but in vivo precision data are limited for the spine and have not been published for the hip. We prospectively performed duplicate dual X-ray absorptiometry measurements of the anteroposterior spine and hip (n = 121) in a diverse female population referred for initial clinical BMD testing. Each scan pair was performed and analyzed by two different technologists (mean interval of 4 d) to obtain standard aBMD. Scan data were reprocessed at a later date to calculate vBMD for the lumbar spine (L2-L4), femoral neck, and total hip in the 87 spines and 82 hips for which we had complete analyzable scan data. We found much worse precision in femoral neck volume (5.2% coefficient of variation [CV]) than in spine volume (2.6% CV; p < 0.003). This contributed to greater error in femoral neck vBMD (3.9% CV) than aBMD (2.3= CV; p < 10(-6)). Total hip aBMD had better precision than vBMD (1.0 and 1.3-2.5% CV; p < 10(-5)). The reverse pattern was seen in the spine with slightly better precision for vBMD than aBMD (1.1 and 1.5% CV; p < 0.002). Volumetric measures of lumbar spine density can be obtained with high precision. Because of poor reproducibility in the femoral neck, the total hip region may be preferable for measuring volumetric bone density in the proximal femur.     

Different indices of fetal growth predict bone size and volumetric density at 4 years of age

We have demonstrated previously that higher birth weight is associated with greater peak and later‐life bone mineral content and that maternal body build, diet, and lifestyle influence prenatal bone mineral accrual. To examine prenatal influences on bone health further, we related ultrasound measures of fetal growth to childhood bone size and density. We derived Z‐scores for fetal femur length and abdominal circumference and conditional growth velocity from 19 to 34 weeks' gestation from ultrasound measurements in participants in the Southampton Women's Survey. A total of 380 of the offspring underwent dual‐energy X‐ray absorptiometry (DXA) at age 4 years [whole body minus head bone area (BA), bone mineral content (BMC), areal bone mineral density (aBMD), and estimated volumetric BMD (vBMD)]. Volumetric bone mineral density was estimated using BMC adjusted for BA, height, and weight. A higher velocity of 19‐ to 34‐week fetal femur growth was strongly associated with greater childhood skeletal size (BA: r = 0.30, p < .0001) but not with volumetric density (vBMD: r = 0.03, p = .51). Conversely, a higher velocity of 19‐ to 34‐week fetal abdominal growth was associated with greater childhood volumetric density (vBMD: r = 0.15, p = .004) but not with skeletal size (BA: r = 0.06, p = .21). Both fetal measurements were positively associated with BMC and aBMD, indices influenced by both size and density. The velocity of fetal femur length growth from 19 to 34 weeks' gestation predicted childhood skeletal size at age 4 years, whereas the velocity of abdominal growth (a measure of liver volume and adiposity) predicted volumetric density. These results suggest a discordance between influences on skeletal size and volumetric density. © 2010 American Society for Bone and Mineral Research     

The effects of gonadectomy on bone size, mass, and volumetric density in growing rats are gender-, site-, and growth hormone-specific.

Peak volumetric bone mineral density (BMD) is determined by the growth in bone size relative to the mineral accrued within its periosteal envelope. Thus, reduced peak volumetric BMD may be the result of reduced mineral accrual relative to growth in bone size. Because sex steroids and growth hormone (GH) influence bone size and mass we asked: What are the effects of gonadectomy (Gx) on bone size, bone mineral content (BMC), areal and volumetric BMD in growing male and female rats? Does GH deficiency (GH-) reduce the amount of bone in the (smaller) bone, i.e., reduce volumetric BMD? Does GH- alter the effect of Gx on bone size and mineral accrual? Gx or sham surgery was performed at 6 weeks in GH- and GH replete (GH+) Fisher 344 male and female rats. Changes in bone size, volume, BMC, areal and volumetric BMD, measured using dual X-ray absorptiometry (DPX-L), were expressed as percentage of controls at 8 months (mean +/- SEM). All results shown were significant (p < 0.05 level) unless otherwise stated. In GH+ and GH- males, respectively, Gx was associated with: lower femur volume (24%, 25%), BMC (43%, 45%), areal BMD (21%, 14%), and volumetric BMD (30%, 28%); lower spine (L1-L3) volume (26%, 28%), BMC (26%, 30%), and areal BMD (28%, 12%), but not volumetric BMD. Following Gx, GH+ females had increased femur volume (11%), no effect on BMC, decreased areal BMD (6%) and decreased volumetric BMD (17%); GH- females had no change in femur volume, but decreased femur BMC (24%), areal BMD (10%), and volumetric BMD (25%). In GH+ and GH- females, respectively, Gx was associated with a decrease in spine (L1-L3) BMC (12%, 15%), areal BMD (16%, 15%), and volumetric BMD (10%, 16%) with no change in volume. Deficits in non-Gx GH- relative to non-Gx GH+ (males, females, respectively) were: femur BMC (49%, 37%), areal BMD (23%, 8%), volume (19%, 19%) and volumetric BMD (37%, 22%); spine (L1-L3) BMC (46%, 42%), areal BMD (37%, 43%), volume (10%, 15%), and volumetric BMD (40%, 33%). Testosterone and GH are growth promoting in growing male rats, producing independent effects on bone size and mass; deficiency produced smaller appendicular bones with reduced volumetric BMD because deficits in mass were greater than deficits in size. At the spine, the reduction in size and accrual were proportional, resulting in a smaller bone with normal volumetric BMD. In growing female rats, estrogen was growth limiting at appendicular sites; deficiency resulted in a GH-dependent increase in appendicular size, relatively reduced accrual, and so, reduced volumetric BMD in a bigger bone. At the spine, accrual was reduced while growth in size was normal, thus volumetric BMD was reduced in the normal sized bone. Understanding the pathogenesis of low volumetric BMD requires the study of the differing relative growth in size and mass of the axial and appendicular skeleton in the male and female and the regulators of the growth of these traits.     

Daily Physical Education in the School Curriculum in Prepubertal Girls during 1 Year is Followed by an Increase in Bone Mineral Accrual and Bone Width—Data from the Prospective Controlled Malmö Pediatric Osteoporosis Prevention Study

The aim of this study was to evaluate a general school-based 1-year exercise intervention program in a population-based cohort of girls at Tanner stage I. Fifty-three girls aged 7–9 years were included. The school curriculum-based exercise intervention program included 40 minutes/school day. Fifty healthy age-matched girls assigned to the general school curriculum of 60 minutes physical activity/week served as controls. Bone mineral content (BMC, g) and areal bone mineral density (aBMD, g/cm²) were measured with dual X-ray absorptiometry (DXA) of the total body (TB), lumbar spine (L2–L4 vertebrae), third lumbar vertebra (L3), femoral neck (FN), and leg. Volumetric bone mineral density (g/cm³) and bone width were calculated at L3 and FN. Total lean body mass and total fat mass were estimated from the TB scan. No differences at baseline were found in age, anthropometrics, or bone parameters when the groups were compared. The annual gain in BMC was 4.7 percentage points higher in the lumbar spine and 9.5 percentage points higher in L3 in cases than in controls (both P < 0.001). The annual gain in aBMD was 2.8 percentage points higher in the lumbar spine and 3.1 percentage points higher in L3 in cases than in controls (both P < 0.001). The annual gain in bone width was 2.9 percentage points higher in L3 in cases than in controls (P < 0.001). A general school-based exercise program in girls aged 7–9 years enhances the accrual of BMC and aBMD and increases bone width.