Differences in bone size and bone mass between black and white 10-year-old South African children

Introduction Black and white South Africans hail from vastly disparate cultural and socio-economic backgrounds the result of which exposes black children to numerous factors known to impact negatively on bone mass. Thus, we studied ethnic differences in bone size and bone mass between 476 10-year-old black and white South African girls and boys (black boys n=182, white boys n=72, black girls n=158, white girls n=64) who formed part of a longitudinal cohort of children born in Johannesburg, South Africa, during 1990. Methods Bone area (BA) and bone mineral content (BMC) were measured at the whole body, total hip, femoral neck, lumbar spine (L1–L4) and mid- and distal radii by dual energy X-ray absorptiometry (DXA). Vertebral heights and metacarpal indices were measured. Anthropometry, skeletal maturity and pubertal development were also assessed. Results After correction for height, weight, gender and puberty, black children had greater BMC at the femoral neck (P<0.0001), total hip (P<0.05) and mid-radius (P<0.001) than white children.. At the whole body, lumbar spine, and distal one-third of the radius, there were no differences in BMC between black and white children after correction for differences in body size. After correction for height and puberty, vertebral heights were less in black children than white children, and cortical areas at the second metacarpal were greater in black children. Conclusion These findings suggest that, at the femoral neck, total hip and mid-radius, these differences are not a result of differences in anthropometry, bone age or pubertal stage, or environmental factors but are most likely to result from genetic differences.     

Judo Practice in Early Age Promotes High Level of Bone Mass Acquisition of Growing Boys' Skeleton

The current study aimed to exhibit effects of judo training for at least 2 yr on bone mass parameters in growing boys. Our population was composed of one hundred and thirty boys in tanner stage 1 and aged 10.52 ± 0.86 yr. Eleven judo players were therefore, excluded from the study because they do not have participate regularly to the judo training sessions during the last 2 yr. The resting sample was divided into two groups: 50 judo players (JU group) and 69 controls (C group). Bone mineral density (BMD), bone mineral content (BMC), and bone area (BA) were evaluated by using dual-photon X-ray absorptiometry on weight-bearing sites: the whole body, lumbar spine (L2-L4), legs, femoral necks and hips and on the non-weight bearing sites: arms and radiuses. Our findings displayed that judo participation was markedly associated with greater values of bone mass parameters in young judo players than control group. Accordingly, the BMD and BA results exhibited significant differences in the whole body, legs, dominant total hip, arms and both whole radiuses in addition to the dominant femoral neck, the non-dominant total hip and except the non-dominant whole radius for the BMC parameter. Additionally, data of the subject within t test has shown significant differences of bone mass parameters only in the non weight-bearing sites in the judo players without any obvious variation in the controls. Differences of BMD observed on the dominant arm and whole radius in addition to the increased BMC values showed in the dominant whole radius compared with their contra-lateral sites in judo players without any marked variation of BA parameters in all sites in both groups. In growing boys, judo practice was obviously associated with osteogenic effects in specific sites.     

Comparisons of body size, composition, and whole body bone mass between North American and South African children.

We compared whole body BMC of 811 black, white, and mixed ancestral origin children from Detroit, MI; Johannesburg, South Africa; and Cape Town, South Africa. Our findings support the role of genetic and environmental influences in the determination of bone mass in prepubertal children. INTRODUCTION: Higher bone mass and lower fracture rates have been shown in black compared with white children and adults in North America. MATERIALS AND METHODS: We compared whole body BMC (WBBMC), whole body fat mass (WBFM), and whole body fat free soft tissue (WBFFST) data between three ethnic groups of children from Detroit, MI (n = 181 white, USW; n = 230 black, USB), Johannesburg, South Africa (n = 73 white, SAW; n = 263 black, SAB), and Cape Town, South Africa (n = 64 mixed ancestral origin, SAM). RESULTS: SAB and SAW groups were slightly older than USW and USB groups (9.5 +/- 0.3 versus 9.3 +/- 0.1 yr); however, USB and USW boys were significantly taller, were heavier, and had a higher BMI than SAM and SAB boys. USB girls were significantly taller than SAB girls and heavier than SAB and SAM girls. In South Africa and the United States, black children had a significantly higher WBBMC than white children, after adjusting for selected best predictors. After adjusting for age, weight, and height, WBBMC was significantly higher in the SAB and SAW boys than in USW and USB and in the SAM group compared with the USW and USB groups. WBFFST and WBFM made significant contributions to a best linear model for log(WBBMC), together with age, height, and ethnicity. The best model accounted for 79% of the WBBMC variance. When included separately in the model, the model containing WBFFST accounted for 76%, and the model containing WBFM accounted for 70%, of the variance in WBBMC. CONCLUSIONS: WBBMC is lower in children of European ancestry compared with African ancestry, irrespective of geographical location; however, South African children have significantly higher WBBMC compared with USB and USW groups, thereby acknowledging the possible contribution of environmental factors. Reasons for the significantly higher WBBMC in the children of mixed ancestral origin compared with the other groups need to be studied further.     

Differences in estimates of change of bone accrual and body composition in children because of scan mode selection with the prodigy densitometer.

Girls of age 10-13 yr with Tanner stage I-III maturation status (n = 155) were measured using the Prodigy (GE Lunar) densitometer. Bone area (BA), bone mineral content (BMC), and bone mineral density (BMD) were assessed for the whole body, lumbar spine, and proximal femur using the Thin (T) and Standard (S) scan modes at years 1 and 3 of the study. The differences obtained between the T and S mode at year 1 were 1-2% for the lumbar spine and proximal femur and 5-11% for the whole body. For those girls whose default mode changed from T at year 1 to S mode at year 3, the estimated gain in BA, BMC, and BMD was 3.4%, 7.6%, and 3.1% respectively, lower than that obtained when scanning with the T mode at both times for the whole body. Small changes in magnitude but large intersubject variability were noted in BA, BMC, and BMD of the lumbar spine and proximal femur when scanned with the default mode of T at year 1 and S at year 3 compared to T or S at both years. Errors of this size are comparable to the changes expected with longitudinal intervention studies and are, therefore, clinically relevant.     

Bone Mass and Bone Size in Pre- or Early Pubertal 10-Year-Old Black and White South African Children and Their Parents

Genetic factors are thought to maintain bone mass in socioeconomically disadvantaged black South Africans. We compared bone mass between environmentally disadvantaged black and advantaged white children and their parents, after determining the most appropriate method by which to correct bone mineral content (BMC) for size. We collected data from 419 healthy black and white children of mean age 10.6 years (range 10.0–10.9), 406 biological mothers, and 100 biological fathers. Whole-body, femoral neck, lumbar spine, and mid- and distal one-third of radius bone area (BA) and BMC were measured by dual-energy X-ray absorptiometry. Power coefficients (PCs) were calculated from the linear-regression analyses of ln(BMC) on ln(BA) and used to correct site-specific BMC for bone size differences. Heritability (½h², %) by maternal and paternal descent was estimated by regressing children’s Z scores on parents’ Z scores. Correcting BMC for height, weight, and BA^PC accounted for the greatest variance of BMC at all skeletal sites. In so doing, BMC in blacks was up to 2.6 times greater at the femoral neck and lumbar spine. Maternal and paternal heritability was estimated to be ~30% in both black and white subjects. These results may in part explain the lower prevalence of fragility fractures at the hip in black South African children when compared to whites. Heritability was comparable between environmentally disadvantaged black and advantaged white South African children and similar to that reported for Caucasians in other parts of the world.     

Fat mass increase in 7-year-old children: More Bone Area but lower Bone Mineral density

The main aims of this study were, to evaluate what effect a change in fat mass (FM) and lean body mass (LBM) has on bone parameters over 2 years’ time, in 7-year-old school children and to see what effect fitness had on bone parameters in these children. A repeated-measures design study was conducted where children born in 1999 from six elementary schools in Reykjavik, Iceland were measured twice. All children attending second grade in these six schools were invited to participate. Three hundred twenty-one children were invited, 211 underwent dual-energy X-ray absorptiometry (DXA) scans at the age of seven, and 164 (78 %) of the 211 had DXA scans again 2 years later. Increase in both FM and LBM was associated with increased total body bone mineral content (BMC) and bone area (BA). An increase in FM was more strongly positively associated with BA while an increase in LBM was more strongly associated with an increase in BMC. An increase in FM was negatively associated with change in bone mineral density (BMD), but an increase in LBM was positively associated with change in BMD. Fitness was positively associated with bone parameters when weight, height and sex were accounted for. The present results suggest that an increase in fat mass over 2 years is associated with an increase in BA and BMC, but a decrease in BMD in the whole body. An increase in LBM accrual, on the other hand, is positively associated with all bone parameters in the body. Fitness is associated with both BMC and BMD but not BA.     

Percent fat mass is inversely associated with bone mass and hip geometry in rural Chinese adolescents

This study was an attempt to examine the phenotypic, genetic, and environmental correlations between percent fat mass (PFM) and bone parameters, especially hip geometry, among 786 males and 618 females aged 13 to 21 years from a Chinese twin cohort. PFM, bone area (BA), bone mineral content (BMC), cross‐sectional area (CSA), and section modulus (SM) were obtained by dual‐energy X‐ray absorptiometry. Multiple linear regression models were used to assess the PFM‐bone relationships. A structural equation model for twin design was used to estimate genetic/environmental influences on individual phenotype and phenotypic correlations. After controlling for body weight and other pertinent covariates, we observed inverse associations between PFM and bone parameters: Compared with the lowest age‐ and gender‐specific tertile of PFM, males in the highest tertile of PFM had lower measures of whole‐body‐less‐head BA (WB‐BA), lumbar spine BA (L₂–L₄‐BA), total‐hip BA (TH‐BA), total‐hip BMC, CSA, and SM (p < .005 for all, adjusted p < .05). Similar inverse associations were observed in females for all the preceding parameters except WB‐BA and L2–L₄‐BA. These associations did not vary significantly by Tanner stages. In both genders, the estimated heritabilities were 80% to 86% for BMC, 67% to 80% for BA, 74% to 77% for CSA, and 64% for SM. Both shared genetics and environmental factors contributed to the inverse PFM‐bone correlations. We conclude that in this sample of relatively lean Chinese adolescents, at a given body weight, PFM is inversely associated with BA, BMC, and hip geometry in both genders, and such associations are attributed to both shared genetic and environmental factors. © 2010 American Society for Bone and Mineral Research     

Growth and Bone Mineral Accretion During Puberty in Chinese Girls: A Five‐Year Longitudinal Study

There are few longitudinal data on bone development during puberty in children with low calcium intake. This 5‐yr longitudinal study showed that, in Chinese girls, the mean apparent calcium retention efficiency during puberty was 40.9%, PHV occurred at 3–0 yr before menarche, and peak bone mineral accretion occurred 1 yr later than PHV. Chinese girls have high calcium retention efficiency during puberty. Introduction: There are few longitudinal data on bone development during puberty in children with low dietary calcium intake. The aim of this study was to examine the rate of growth and bone mineral accretion and study the predictors of total body BMC during puberty in a 5‐yr longitudinal study with Chinese girls. Materials and Methods: Ninety‐two girls, 9.5–10.5 yr of age at baseline, from the unsupplemented control group of a school milk intervention trial were included in this analysis. Data on anthropometric measurements, total body BMC as assessed by DXA, and calcium intake as assessed by a 3‐day food record were obtained at baseline and 1, 2, 4, and 5 yr. Results: The mean age of menarche was 12.1 ± 1.0 yr. The mean annual rate of bone mineral accretion was 197.4 g/yr during the follow‐up period, representing a calcium accretion rate of 162.3 mg/d. This calcium retention rate and the average dietary calcium intake of 444.1 mg/d gave an apparent calcium retention efficiency of 40.9%. Peak height velocity (PHV) occurred at 3–0 yr before menarche. Peak bone mineral accretion occurred 1 yr later than PHV. There was a decrease in size‐corrected BMD in the year before menarche. In the linear mixed‐effects model analysis containing body size and lifestyle factors, we found that height, body weight, and calcium intake were significant independent predictors of total body BMC. Conclusions: Chinese girls with low habitual dietary calcium intake have high calcium retention efficiency during puberty. Because calcium intake is a significant predictor of total body BMC, increasing dietary calcium intake may have beneficial effects on bone mineral accretion in these girls.     

Analysis of Bone Mineral Content in Horizontally HIV-Infected Children Naïve to Antiretroviral Treatment

AbstractLow bone mass is a frequent finding in HIV-infected individuals. Reduced bone mass has been found in vertically infected children who are receiving antiretroviral treatment. Little is known about bone mass in horizontally infected young patients who are naïve to antiretroviral therapy. We measured the bone mineral content (BMC) at the lumbar spine and in the whole skeleton by using dual-energy X-ray absorptiometry (DXA) in 16 HIV-infected children (age 9.3 ± 3.9 years) naïve to antiretroviral treatment, and in 119 healthy children (age 9.7 ± 3.3 years). Thirteen patients were also pair-matched by anthropometric measures, sex, and age with healthy children. Median spine BMC of HIV-infected children was 14.9 g (8.2–39.2 g), and whole body BMC was 1106.1 g (55.5–2344.1 g). Spine BMC of healthy children was 18.6 g (6.8–52.2 g), and whole body BMC was 1213.5 g (541.0–2722.0 g). Multivariate analysis showed a mean difference of spine BMC values of 0.004 g (P = 0.64) between the two groups. Similarly, the whole body BMC difference between the two groups (0.001 g) was not statistically significant (P = 0.55). Mean spine BMC measurements in the case-control evaluation were 21.1 g (9.7 g) (patients), and 22.3 g (6.9 g) (controls). Whole body BMC measurements of patients and controls were 1258.5 g (539.6 g) and 1311.1 g (479.2 g), respectively. In both cases the differences were not significant. The duration of HIV infection did not relate to BMC values. In conclusion, horizontally HIV-infected children naïve to antiretroviral therapy have bone mineral measurements comparable to those of healthy children.     

Fetal and Childhood Growth Patterns Associated with Bone Mass in School‐Age Children: The Generation R Study

Low birth weight is associated with lower bone accrual in children and peak bone mass in adults. We assessed how different patterns of longitudinal fetal and early childhood growth influence bone properties at school age. In 5431 children participating in a population‐based prospective cohort study, we measured fetal growth by ultrasound at 20 and 30 weeks gestation, and childhood growth at birth, 1, 2, 3, and 4 years of age. We analyzed these growth measurements in relation to total body (less head) BMD measured by DXA at age 6. We used conditional growth modeling; a technique which takes into account correlation between repeatedly measured growth measures. Our results showed that estimated fetal weight gain, femur length growth between 20 and 30 weeks of gestation, femur length growth between 30 weeks and birth, as well as all height and weight growth measurements from birth to 4 years of age were all positively associated with BMC, bone area (BA), and BMD (all p < 0.01). Fetal femur length growth between 30 weeks and birth was positively associated with BMC and BA (both p < 0.001), but not with BMD. Overall, childhood growth measurements exerted a larger influence on bone measures than fetal growth measures. The strongest effect estimate was observed during the first year of life. Children born small (<10th percentile) for gestational age (SGA) had lower BMC and BA, but not BMD, than children born appropriate for gestational age (AGA), whereas children born large (>90th percentile) for gestational age (LGA) had higher BMC and BA (all p < 0.001). These differences were no longer present in children showing subsequent accelerated and decelerated infant growth, respectively. We conclude that both fetal and childhood growth patterns are associated with bone mineral accrual, showing the strongest effect estimates in infancy . Compensatory infant growth counteracts the adverse consequences of fetal growth restriction on bone development. © 2014 American Society for Bone and Mineral Research.     

Bone Assessment in Children: Comparison of Fan-Beam DXA Analysis

The newest version of whole body dual-energy X-ray absorptiometry (DXA) analysis software from Hologic (Discovery 12.1) is designed to enhance bone detection in smaller subjects. We re-analyzed 1127 pediatric scans (ages 1.8-18.5 yr) previously analyzed using software version 11.2. Regression analysis compared new and original results for bone area (BA), bone mineral content (BMC), bone mineral density (BMD), and DXA-derived body weight. Changes in total and regional bone results were compared with age, weight, and height. New results were highly correlated with original analyses (R2 > or = 0.9), but there were large differences at the individual subject level. The BA and BMC values increased in subjects less than 40 kg weight, resulting in a lower BMD. Original and new results were equivalent by about age 14 yr in both genders. Regional bone data showed the greatest changes in the legs. The newest software produces significant changes in bone values in subjects weighing less than 40 kg, compared with earlier versions. This effect increases with decreasing body weight. This will impact interpretation of longitudinal pediatric DXA studies, as well as existing pediatric whole body bone reference databases. Investigators must recognize which DXAsoftware version they are using, and which version produced any reference database they may use for comparison.     

Bone density interpretation and relevance in Caucasian children aged 9-17 years of age: insights from a population-based fracture study.

The interpretation of bone density measurement in children is difficult due to a number of factors including rapid change in body size and uncertain clinical significance of bone density in children. This study asked two questions. (1) Is there a preferred bone density measurement site or type for fracture risk in children? (2) What is the best way to interpret bone density in children? This population-based case control study included 321 upper limb fracture cases and 321 class- and sex- matched randomly selected controls. Bone density at the hip, spine, and total body (including the arm) was measured by a Hologic QDR2000 densitometer (Waltham, MA) and examined as bone area (BA), bone mineral content (BMC), bone mineral density (BMD), bone mineral apparent density (BMAD), and BMC/lean mass (BMCLM). The only dual-energy X-ray absorptiometry (DXA) variables that were consistently associated with fracture risk in both boys and girls were spine BMD and BMAD for total upper limb fractures, and spine and hip BMAD for wrist and forearm fractures. No significant associations were observed for BA and BMCLM and inconsistent associations for BMC and other BMD sites. Five-yr fracture risk varied from 15–24% depending on site and gender in a child with a Z-score of -3. In the controls, all DXA variables were associated with age, height, and weight, but the weakest associations were with BMAD. In conclusion, in this study the spine BMAD had the strongest and most consistent association with upper limb fracture risk in children. The associations with age and body size imply that age specific Z-scores will be the most convenient for interpretation of DXA measures in children. Five-yr wrist and forearm fracture risk has potential as a clinical endpoint of immediate relevance.     

Comparison of Site-Specific Bone Mass Indices in South African Children of Different Ethnic Groups

This study reports on ethnic differences in bone mass before and after adjusting for differences in body size and bone area (BA). Lumbar spine (LSBMC), proximal femur (PFBMC) and femoral neck (FNBMC) bone mineral contents were measured in black (‘black’; n = 263) and white (‘white’; n = 73) children from Johannesburg and children of mixed ancestral origin (‘mixed’; n = 64) from Cape Town, South Africa. Geometric estimates and the power coefficient from the regression analyses of BMC on BA were calculated. After adjusting for age, weight, and height, LSBMC in girls and FNBMC in girls and boys were greatest in mixed, followed by black and then white, groups. Mixed boys and girls also had greater PFBMC than their black and white peers, but only in the boys was PFBMC greater in the black than the white groups. When including BA in the adjustment, differences remained at the FN in boys and girls, and the LS and PF in girls, but disappeared at the PF in mixed and black boys. The difference in LSBMC between mixed and black boys became significant after adjustment for age, weight, height, and BA. Geometric estimates at the femoral neck were greater in the mixed group. Power coefficients were greater in the white group, suggesting differences in shape or bone distribution. In conclusion, this study suggests that, in addition to differences in BMC, differences in bone strength and geometry are present which might confer advantages to the bone of mixed-ancestry children.     

Bone mineral accrual in 4‐ to 10‐year‐old precompetitive,recreational gymnasts: A 4‐year longitudinal study

Competitive female gymnasts have greater bone mineral measures than nongymnasts. However, less is known about the effect of recreational and/or precompetitive gymnastics participation on bone development. The purpose of this study was to investigate whether the differences previously reported in the skeleton of competitive female gymnasts are also demonstrated in young children with a current or past participation history in recreational or precompetitive gymnastics. One hundred and sixty‐three children (30 gymnasts, 61 ex‐gymnasts, and 72 nongymnasts) between 4 and 6 years of age were recruited and measured annually for 4 years (not all participants were measured at every occasion). Total‐body (TB), lumbar spine (LS), and femoral neck (FN) bone mineral content (BMC) were measured by dual‐energy X‐ray absorptiometry (DXA). Multilevel random‐effects models were constructed and used to predict differences in TB, LS, and FN BMC between groups while controlling for differences in body size, physical activity, and diet. Gymnasts had 3% more TB and 7% more FN BMC than children participating in other recreational sports at year 4 (p < .05). No differences were found at the LS between groups, and there were no differences between ex‐gymnasts' and nongymnasts' bone parameters (p > .05). These findings suggest that recreational and precompetitive gymnastics participation is associated with greater BMC. This is important because beginner gymnastics skills are attainable by most children and do not require a high level of training. Low‐level gymnastics skills can be implemented easily into school physical education programs, potentially affecting skeletal health. © 2011 American Society for Bone and Mineral Research.     

Enhanced Bone Mass and Physical Fitness in Prepubescent Basketball Players

The aim of this study was to examine the effect of basketball practice on bone acquisition in the prepubertal age. In total, 48 prepubescent male basketball players aged 11.1 ± 0.8 yr, Tanner stage 1, were compared with 50 controls matched for age and pubertal stage. Areal bone mineral density, bone mineral content (BMC), and bone area (BA) in deferent sites associated with anthropometric parameters were measured by dual-energy X-ray absorptiometry. Running and jumping tests were performed. Analysis of Student's impaired t-test revealed that basketball players attained better results in all physical fitness tests (p < 0.05). They also exhibited significantly greater BMC and BA in whole body, upper and lower extremities, trochanter, total hip, and whole right and left radius (p < 0.001) compared with the controls. No significant differences were observed between groups in right and left ultradistal and third distal radius and spinal regions, BMC, and BA, whereas a significant positive correlation was reported between lean mass, BMC, and BA of lower limbs. In summary, basketball practice in prepubertal age is associated with improved physical fitness and enhanced lean and bone mass in loaded sites.     

Positive, site-specific associations between bone mineral status, fitness, and time spent at high-impact activities in 16- to 18-year-old boys

The incidence of hip and forearm fracture in elderly men in the United Kingdom is a public health issue, but there is limited knowledge on lifestyle factors affecting male bone health. The aim of this cross-sectional study was to evaluate the relationships between whole body and regional bone mineral status and self-reported participation time in no-, low-, moderate-, and high-impact activities and fitness measurements in 16- to 18-year-old boys. One hundred twenty-eight boys underwent absorptiometry (DXA) measurements (Hologic QDR 1000W) of bone mineral content (BMC), bone area (BA), and bone mineral density (BMD) at the whole body, hip, spine, and forearm. They also completed the EPIC (European Prospective Investigation of Cancer) physical activity questionnaire, which allowed categorization of activities according to impact and aerobic intensity. Fitness and strength were assessed in each subject using estimated VO2 max, grip strength, and back strength. Significant positive relationships were found between BMC, BA, and BMD and the fitness and strength measurements and participation time in high-impact sports at most skeletal sites. The relationships were further examined after adjustment of BMC for height, weight, and bone area, thereby minimizing the influence of body and bone size on these relationships. VO2 max was a significant positive determinant of size-adjusted BMC at the whole body, the ultradistal and one-third radius, and all the hip sites, except the trochanter. Size-adjusted BMC at the forearm sites and trochanter was significantly positively associated with grip strength. Size-adjusted BMC at the whole body and all the hip sites was significantly positively associated with time spent at high-impact activities. Differences in size-adjusted BMC across thirds of time spent at high-impact activities were also examined. Boys in the highest third of high-impact activity had significantly greater size-adjusted whole body BMC and total hip BMC compared to subjects in the lowest third [+3.4 (1.2)% for whole body and +8.5 (2.2)% for hip, both P = 0.001]. Boys in the highest third of high-impact activity spent most activity time jogging, playing tennis, football and rugby, basketball, and exercising with weights. Back strength and lean mass were significantly greater in subjects in the highest third compared to those in the middle (P = 0.02) and lowest third (P = 0.03). No significant differences were found between subjects in each third of high-impact activity for potential confounders including TV viewing, calcium intake, body fat, and height. These findings indicate that participation of male adolescents in a range of high-impact activities for 1 h or more a day is associated with greater bone size and mineral content, especially at the hip.     

Bone mineral density in prepubertal obese and control children: relation to body weight,lean mass,and fat mass

The aim of the study was to determine the influence of obesity on bone status in prepubertal children. This study included 20 obese prepubertal children (10.7 +/- 1.2 years old) and 23 maturation-matched controls (10.9 +/- 1.1 years old). Bone mineral area, bone mineral content (BMC), bone mineral density (BMD), and calculation of bone mineral apparent density (BMAD) at the whole body and lumbar spine (L1-L4) and body composition (lean mass and fat mass) were assessed by DXA. Broadband ultrasound attenuation (BUA) and speed of sound (SOS) at the calcaneus were measured with a BUA imaging device. Expressed as crude values, DXA measurements of BMD at all bone sites and BUA (69.30 versus 59.63 dB/MHz, P < 0.01) were higher in obese children. After adjustment for body weight and lean mass, obese children displayed lower values of whole-body BMD (0.88 versus 0.96 g/cm2, P < 0.05) and BMC (1190.98 versus 1510.24 g, P < 0.01) in comparison to controls. When results were adjusted for fat mass, there was no statistical difference between obese and control children for DXA and ultrasound results. Moreover, whole-body BMAD was lower (0.086 versus 0.099 g/cm3, P < 0.0001), whereas lumbar spine BMAD was greater (0.117 versus 0.100 g/cm3, P < 0.001) in obese children. Thus, it was observed that, in obese children, cortical and trabecular bone displayed different adaptation patterns to their higher body weight. Cortical bone seems to enhance both size and BMC and trabecular bone to enhance BMC. Finally, considering total body weight and lean mass of obese children, these skeletal responses were not sufficient to compensate for the excess load on the whole body.     

A 5‐Year Cohort Study of the Effects of High Protein Intake on Lean Mass and BMC in Elderly Postmenopausal Women

Long‐term effects of high dietary protein intake on muscle and bone structure in the elderly are not clear. The aim of this study was to investigate the relationship between baseline protein intake and lean mass and BMC 5 yr later in a cohort of elderly postmenopausal women. A total of 862 community‐dwelling women 75 ± 3 yr of age provided baseline data including nutrient intake assessed by a food frequency questionnaire. At 5 yr, upper arm muscle area (UAMA) and body composition using DXA were measured. Baseline protein intake was 81 ± 28 g/d (1.2 ± 0.4 g/kg/d), contributing 19 ± 3% of total energy intake. There were positive correlations between baseline protein intake and whole body and appendicular bone‐free lean mass and BMC (r = 0.14–0.18, p < 0.001) and UAMA (r = 0.08, p < 0.05). Compared with those in the lowest tertile of protein intake (<66 g/d), women in the top tertile (>87 g/d) had 5.4–6.0% higher whole body and appendicular lean mass and UAMA and 5.3–6.0% higher whole body and appendicular BMC. These effects remained after adjusting for potential confounders. However, the effect on BMC disappeared after further adjustment for lean mass. This study shows that high protein intake is associated with long‐term beneficial effects on muscle mass and size and bone mass in elderly women. The protein effect on bone may be partly mediated by its effects on muscle.     

Bone mass and density in preadolescent boys with and without Down syndrome

Summary

Preadolescent boys with Down syndrome at 7–10 years of age have lower bone mass and density in the pelvis than age-matched children without Down syndrome. However, bone mass and density of total body less head and lumbar spine are not different between these two groups.

Introduction

This study aimed to assess bone mineral content (BMC) and density (BMD) in preadolescent boys with and without Down syndrome (DS) at 7–10 years of age.

Methods

Eleven preadolescent boys with DS and eleven age-matched children without DS participated in this study. Dual-energy X-ray absorptiometry was used to measure BMC and BMD in whole body and lumbar spine. Both BMC and BMD of total body less head (TBLH) and lumbar spine (vertebrae L2–L4) were compared between the two groups, with and without adjusting for physical characteristics such as bone area, body height, and total lean mass. Two bone mineral apparent density (BMAD) variables were calculated to estimate volumetric BMD in the lumbar spine.

Results

Both BMC and BMD in the pelvis were lower in the DS group, after adjusting for physical characteristics. However, with and without adjusting for physical characteristics, the two groups were not different in BMC and BMD of the arms, legs, and TBLH from the whole body scan and in BMC, BMD, and BMAD of the lumbar spine from the lumbar spine scan.

Conclusions

These findings indicate that the pelvis may be the first site to show the significant difference in BMC and BMD between preadolescent boys with and without DS. It also suggests that significantly lower BMC and BMD in whole body and lumbar spine, which is usually observed in young adults with DS, may not occur before adolescence.     

Initial years of recreational artistic gymnastics training improves lumbar spine bone mineral accrual in 4- to 8-year-old females.

Gymnasts' bone mineral characteristics are generally not known before starting their sport. Prepubertal females who enrolled in beginning artistic gymnastics (n = 65) had lower bone mineral than controls (n = 78). However, 2 years of gymnastics participation versus no participation led to a significantly greater accrual of forearm bone area and lumbar spine areal BMD. INTRODUCTION: The skeletal response to exercise in children compared with adults is heightened because of the high bone turnover rate and the ability of bone to change its size and shape. Whereas child gymnasts generally have greater rates of bone mineral accrual compared with nongymnasts, it is unknown if some of these skeletal advantages are present before the onset of training or are caused entirely by training. MATERIALS AND METHODS: Changes in bone area (BA; cm2), BMC (g), and areal BMD (aBMD; g/cm2) over 24 months were examined in prepubertal females, 4-8 years of age, who selected to perform recreational gymnastics (GYM; n = 65), nongymnastic activities, or no organized activity (CON; n = 78). Participants had essentially no lifetime history of organized athletic participation (< 12 weeks). Pubertal maturation was assessed annually by a physician. Total body, lumbar spine, total proximal femur, and forearm BA, BMC, and aBMD were measured every 6 months using DXA (Hologic QDR-1000W). Independent samples t-tests determined baseline group differences. Nonlinear mixed effects models were used to model 24-month changes in bone data. In subset analyses, high-level gymnasts advancing to competition (HLG; n = 9) were compared with low-level nonadvancing gymnasts (LLG; n = 56). RESULTS: At baseline, GYM were shorter, lighter, and had lower BA, BMC, and aBMD compared with CON (p < 0.05), whereas HLG did not differ significantly in these measurements compared with LLG (p > 0.05). Controlling for differences in race, baseline measures of body mass, height, and calcium intake, and change in breast development beyond stage II at 24 months, GYM had greater long-term (asymptotic) mean responses for total body aBMD and forearm BMC (p < 0.04) and greater rates of increase in the mean responses of lumbar spine aBMD and forearm BA compared with CON over 24 months. Over time, forearm BA increased to a greater extent in HLG compared with LLG (p < 0.01). CONCLUSIONS: Females participating in recreational gymnastics initiated during childhood have enhanced bone mineral gains at the total body, lumbar spine, and forearm over 24 months. Higher-level training promotes additional gains in forearm BA.