The influence of anthropometry and body composition on children's bone health: the childhood health, activity and motor performance school (the CHAMPS) study, Denmark

Sex-specific effects of a Mediterranean diet on lower limb bone strength in Polish children

Lifestyle factors have the potential to influence bone health in various ways, whether positively or negatively. As osteoporosis is believed to originate in early years, it is therefore essential to indicate factors that may positively affect bone health during childhood. The aim of our study was to investigate the effects of early and current diet, vitamin D supplementation, and BMI z-score on bone properties in a group of children aged 3-7 years. A cross-sectional sample of 205 preschoolers and their parents participated in the study. Dietary assessment was made using a modified version of the Polish-adapted Mediterranean Diet score (MVP-aMED) on the basis of the data from food frequency questionnaire (FFQ), filled out by the parents. Quantitative ultrasound (QUS) was used in the assessment of bone properties. In the sex-stratified analysis, significant associations were observed between MVP-aMED score (β = 0.193, 95 % CI: 0.005, 0.237; p = 0.04), BMI z-score (β = -0.318, 95 % CI: -1.455, -0.039; p = 0.04) and QUS z-score, exclusively among girls. After adjustment, only the relationship with diet remained significant (β = 0.209, 95 % CI: 0.007, 0.255; p = 0.04), suggesting that a higher adherence to the Mediterranean Diet may be associated with better bone properties in girls aged 3-7 years old. Our results emphasize the importance of fostering healthy dietary habits and maintaining proper weight in children in order to promote optimal bone development.

Serum Oxytocin Levels Decrease 12 Months Following Sleeve Gastrectomy and Are Associated with Decreases in Lean Mass

Oxytocin (OXT), an anorexigenic hormone, is also bone anabolic. Further, OXT administration results in increases in lean mass (LM) in adults with sarcopenic obesity. We examine, for the first time, associations of OXT with body composition and bone endpoints in 25 youth 13-25 years old with severe obesity who underwent sleeve gastrectomy (SG) and 27 non-surgical controls (NS). Forty participants were female. Subjects underwent fasting blood tests for serum OXT and DXA for areal bone mineral density (aBMD) and body composition. At baseline, SG vs. NS had higher median body mass index (BMI) but did not differ for age or OXT levels. Over 12 months, SG vs. NS had greater reductions in BMI, LM, and fat mass (FM). OXT decreased in SG vs. NS 12 months post-SG. While baseline OXT predicted a 12-month BMI change in SG, decreases in OXT levels 12 months post-SG were not associated with decreases in weight or BMI. In SG, decreases in OXT were positively associated with decreases in LM but not with decreases in FM or aBMD. Loss of LM, a strong predictor of BMD, after bariatric surgery may reduce functional and muscular capacity. OXT pathways may be targeted to prevent LM loss following SG.

Association of total body fat and fat distribution with bone mineral density among children and adolescents aged 6-17 years from Guangzhou, China

This study aimed to assess the associations of total body fat and fat distribution with bone mineral density (BMD) among children and adolescents in this cross-sectional study. A total of 1032 boys and 897 girls aged 6-17 years were enrolled between May 2019 and June 2019 in Guangzhou, China. BMD, total body fat (fat mass index [FMI] and body fat percentage [BF%]), and fat distribution (trunk-to-limb and android-to-gynoid ratios) were measured by dual-energy X-ray absorptiometry. Inverse probability of treatment weighting regression was used to explore the association between fat and BMD. Traditional regression of covariate adjustment was applied as sensitivity analysis. Regression with inverse probability weighting suggested BF% and android-to-gynoid ratio were negatively associated with BMD in boys (β =  - 0.12 and - 0.16, respectively; P < 0.05). Android-to-gynoid ratio was also inversely associated with BMD in girls (β =  - 0.08, P < 0.05). When stratified by age, the negative associations were retained in boys aged 12-17 years (β =  - 0.23 and - 0.25, respectively; P < 0.001). But for girls, it showed a positive association of FMI with BMD in the 6-9 years group (β = 0.33, P < 0.001) and a negative association between the android-to-gynoid ratio and BMD in the 10-17 years group (β =  - 0.10, P < 0.05). Traditional regression supported the robustness of the results.  Conclusion: Total body fat is positively associated with BMD in younger girls but inversely associated in older boys. As for abdominal adipose, it is associated with lower BMD in both older boys and girls. What is Known: • The lean mass has been consistently positively associated with bone mineral density (BMD) among children and adolescents. However, the impact of fat mass on BMD remained controversial. • Beyond total body fat, site-specific fat mass, especially abdominal adiposity, might impede bone formation. What is New: • The associations of total body fat and fat distribution with BMD in children and adolescents were gender- and age-specific. • More attention should be paid to the abdominal fat accumulation to promote bone health in older children.

Sex differences in bone mineral content and bone geometry accrual: a review of the Paediatric Bone Mineral Accural Study (1991-2017)

CONTEXT

Girls' and boys' growth patterns differ in timing and tempo, and they have different lifestyles with regards to diet and physical activity. These factors have all been linked with bone mineral accrual.

OBJECTIVE

To identify the associations of boys' and girls' growth, maturation, and lifestyle choices relating to parameters of bone geometry and mineral accrual.

METHODS

Between 1991 and 1993, 251 children aged 8-15 years were recruited into a mixed-longitudinal cohort study (The Paediatric Bone Mineral Accrual Study (PBMAS)) and followed repeatedly over 26 years.

RESULTS

It was found that girls matured approximately two years earlier than boys (11.8 vs. 13.4 years) but on average were shorter, had less lean mass and had greater fat mass (p < 0.05). There was a dissociation between the growth of bone and its mineralisation in both sexes. Boys had greater bone mass and bone geometry (p < 0.05). Both a healthy childhood diet and high levels of physical activity were associated with improved bone parameters.

CONCLUSIONS

Most, but not all, of the sex differences observed, were explained by height and lean mass differences. The importance of diet and physical activity on obtaining optimal bone mass during adolescence in both sexes was also paramount.

Association of Body Compositions and Bone Mineral Density in Chinese Children and Adolescents: Compositional Data Analysis

The purpose of this study was to investigate the relationship between body compositions and bone mineral density (BMD) and the effect of composition substitution among Chinese children and adolescents without the influence of multicollinearity. A dual-energy X-ray absorptiometry scan was used to determine the amount of truncal fat (TF), nontruncal fat (NTF), fat-free mass (FFM), and BMD. The compositional data analysis and the compositional proportional substitution analysis were conducted to determine the effect of each part of body compositions on BMD and its substitution effects. Four hundred sixty-six (466) (boys: 51.9%) participants completed this cross-sectional study. For girls, in the overweight group, the relationship between TF and the BMD was positive (β = 2.943e - 01, p = 0.006) while the NTF showed the opposite trend (β = -2.358e - 01, p = 0.009). When 4% NTF or FFM was substituted by TF, the BMD increased by about 0.1 and 0.05 units (p < 0.05), respectively. For boys, the association between FFM and BMD was statistically positive (β = 4.091e - 02, p = 0.0001). There was a positive correlation between TF and BMD (β = 7.963e - 02, p = 0.036). But with the increase of BMI, this correlation shifted in the opposite direction. In conclusion, compared to TF and NTF, FFM had a better protective effect on BMD, especially for boys. The risk of NTF accumulation on BMD was greater than that of TF accumulation. Compared with girls, boys were more sensitive to the amount of TF.

Relationship between the changes over time of bone mass and muscle health in children and adults: a systematic review and meta-analysis

Background

Various cross-sectional studies provide an abundance of evidence that shows a relationship between bone quantity and muscle health. However, one question remains, less-often studied: is their development - or decline – associated? The aim of the research was to conduct a systematic review and meta-analysis to summarize the studies exploring the association between changes in bone mineral density (BMD) and changes in muscle parameters (registration CRD42018093813).

Methods

We searched for prospective studies, both in children and adults, by consulting electronic databases (Ovid-MEDLINE, Ovid-AMED, Scopus). Each review steps were performed by two independent reviewers. For outcomes reported by less of 3 studies, we synthetized the results narratively. In other cases, a meta-analysis was performed, giving an overall r coefficient and its 95% confidence interval (CI).

Results

Fifteen papers were included. In connection with the change of BMD, 10 studies concerned the parallel change of lean mass, 4 were about grip strength, and 1 was about physical performance. Children were the population of interest for 5 studies, while the aging population was the focus of the other studies. The correlation between hip BMD and lean mass was significant, with an overall coefficient r = 0.37 (95% CI 0.23–0.49). High heterogeneity was observed between studies but the length of follow-up, sex and study quality did not seem to significantly influence results. The systematic review allowed some other highlights: a significant link between changes in BMD and changes in muscle strength was observed (p-value < 0.05 in the 4 studies), in addition to changes in performance (1 study, r = 0.21, p-value = 0.004).

Conclusion

Despite the heterogeneity between studies, we highlighted a significant association between the change of BMD and the change of various muscle parameters. Future studies should investigate preventive and therapeutic strategies that are based on a single entity: the ‘muscle-bone unit’.

Bone mineral density and vitamin D status in children with remission phase of steroid-sensitive nephrotic syndrome

Children with idiopathic nephrotic syndrome are primarily treated with glucocorticoids (GCs), but long-term GC use can lead to undesired side effects. We investigated the bone mineral density (BMD) and 25-hydroxyvitamin D (25-OH D) levels in children with the remission phase of steroid-sensitive nephrotic syndrome (SSNS). This study included 32 patients with SSNS who had not received GC treatment in the last 6 months and a control group of 20 healthy children. Serum levels of calcium, phosphate, alkaline phosphatase, 25-(OH)D, and parathyroid hormone (PTH) were measured. BMD was determined in the lumbar spinal region using dual-energy X-ray absorptiometry (DEXA). Serum 25-(OH)D levels were lower in the SSNS patients than in the healthy children (P <0.05), with 22 patients (68.8%) having Z-scores <-1. The Z-scores were positively correlated with 25-(OH)D levels (r = 0.424, P <0.05). PTH levels were higher in patients with osteoporosis than in patients with Z-scores ≥-1 (P <0.05). Bone mineral content and BMD were positively correlated with the age of diagnosis (P <0.01). Receiver-operating characteristic curve analysis showed that the cutoff value of 25-(OH)D levels for predicting low BMD was 14.67 ng/mL with a sensitivity of 90% and a specificity of 64%. The area under the curve (AUC ± standard error) was 0.868 ± 0.064 (95% confidence interval: 0.742-0.994, P = 0.001). Decreased 25-(OH)D levels and the negative effects of long-term GC treatment on BMD persist in SSNS remission phase. Levels of 25-(OH)D <14.67 ng/mL could predict abnormal DEXA scans in children with SSNS remission phase.

Bone mass development is sensitive to insulin resistance in adolescent boys

PURPOSE

Insulin resistance may exert a negative influence on bone mass in childhood and adolescence. The objective was to assess the association between insulin resistance and total body less head (TBLH) bone mineral content (BMC) and to investigate whether body composition, physical activity or osteocalcin levels may influence this association.

METHODS

A longitudinal study with follow-up over more than 6 years was performed and included 562 apparently healthy participants with a mean age of 9.6 years at baseline. Participants underwent DXA scanning at baseline. At the two follow-ups, participants had performed another DXA scanning, had blood samples taken for fasting insulin, glucose and osteocalcin and had physical activity measured with an accelerometer. HOMA-IR was calculated as an index of insulin resistance.

RESULTS

HOMA-IR was negatively associated with TBLH BMC in boys at follow-ups (β = -31.4, p < 0.001) after adjustment for maturity, height, bone area, and baseline level of TBLH BMC. The negative association remained almost unchanged after further adjustments for body composition and physical activity. No association between HOMA-IR and TBLH BMC was found in girls.

CONCLUSION

Insulin resistance may be detrimental for bone development through puberty in boys independent of body composition and the level of physical activity.

Individualized evaluation of lumbar bone mineral density in children with cerebral palsy

Lumbar spine bone mineral density (LS-BMD) assessed by dual-energy X-ray absorptiometry (DXA) is used in children with cerebral palsy (CP) to evaluate bone health. LS-BMD results in children with CP are influenced significantly by their height, BMI, and mobility level. An adjustment for these parameters might improve the clinical significance of the method.

PURPOSE/INTRODUCTION

DXA evaluation is considered useful in children with CP to assess bone health. For this purpose, LS-BMD is often used. The aim of the study was to estimate the effect of height, BMI, and reduced mobility level of children with CP on LS-BMD and to develop a method to adjust individual results of LS-BMD for these factors.

METHODS

We conducted a monocentric retrospective analysis of data collected in children and adolescents with CP, who participated in a rehabilitation program and had no history of recurrent fractures. The DXA scan was part of the routine examination for participants older than 4 years of age. The relationship between height and BMI for age Z-scores and age-adjusted LS-BMD Z-scores was analyzed.

RESULTS

LS-DXA scans of 500 children and adolescents with CP (Gross Motor Function Classification System levels I-V) were included in the statistical analysis (217 female). The mean age was 9.4 years (± 3.7 years). Children with moderate to severe CP had significantly (p < 0.001) lower LS-BMD Z-scores than children with mild CP. We provided nomograms to adjust individual LS-BMD results to their height, BMI, and mobility level.

CONCLUSIONS

LS-BMD results in children with CP were influenced significantly by their height, BMI, and mobility level. An adjustment of the LS-BMD results to height, BMI, and mobility level might improve the clinical significance of an individual result.

Assessing the genetic correlations between early growth parameters and bone mineral density: A polygenic risk score analysis

OBJECTIVE

The relationships between early growth parameters and bone mineral density (BMD) remain elusive now. In this study, we performed a large scale polygenic risk score (PRS) analysis to evaluate the potential impact of early growth parameters on the variations of BMD.

METHODS

We used 2286 Caucasian subjects as cohort 1 and 3404 Framingham Heart Study (FHS) subjects as cohort 2 in this study. BMD at ulna & radius, hip and spine were measured using dual energy X-ray absorptiometry. BMD values were adjusted for age, sex, height and weight as covariates. Genome-wide single-nucleotide polymorphism (SNP) genotyping of the 2286 Caucasian subjects was performed using Affymetrix Human SNP Array 6.0. The GWAS datasets of early growth parameters were driven from the Early Growth Genetics Consortium, including birth weight (BW), birth head circumference (BHC), childhood body mass index (CBMI), pubertal height growth related indexes and tanner stage. Polygenic Risk Score (PRSice) and linkage disequilibrium (LD) score regression analysis were conducted to assess the genetic correlation between early growth parameters and BMD.

RESULTS

We detected significant genetic correlations in cohort 1, such as total spine BMD vs. CBMI (p value = 1.51 × 10^-4, rg = 0.4525), right ulna and radius BMD vs. CBMI (p value = 1.51 × 10^-4, rg = 0.4399) and total body BMD vs. tanner stage (p value = 7.00 × 10^-4, rg = -0.0721). For cohort 2, significant correlations were observed for total spine BMD vs. height change standard deviation score (SDS) between 8 years and adult (denoted as PGF + PGM) (p value = 3.97 × 10^-4, rg = -0.1425), femoral neck BMD vs. the timing of peak height velocity by looking at the height change SDS between age 14 years and adult (denoted as PTF + PTM) (p value = 7.04 × 10^-4, rg = -0.2185), and total spine BMD vs. PTF + PTM (p value = 6.86 × 10^-4, rg = -0.2180).

CONCLUSION

Our study results suggest that some early growth parameters could affect the variations of BMD.

Individualized evaluation of lumbar bone mineral density and bone mineral apparent density in children and adolescents

Lumbar spine bone mineral density (LS-BMD) assessed by dual-energy X-ray absorptiometry (DXA) is used in children to evaluate bone health. LS-BMD results in children are influenced significantly by height and BMI. An adjustment for these parameters may improve the clinical use of the method.

PURPOSE/INTRODUCTION

DXA evaluation is considered useful in children to assess bone health. For this purpose, lumbar spine bone mineral density (LS-BMD) and bone mineral apparent density (LS-BMAD) are often used. The aim of the study was to estimate the effect of height and BMI on LS-BMD and LS-BMAD in children and adolescents and to develop a method to adjust individual results for these factors.

METHODS

As part of the National Health and Nutrition Examination Survey (NHANES) study, between the years 2005 and 2010 lumbar DXA scans on randomly selected Americans from 8 to 20 years of age were carried out. From all eligible DXA scans, three major US ethnic groups were evaluated (Non-Hispanic Whites, Non-Hispanic Blacks, and Mexican Americans) for further statistical analysis. The relationship between height as well as BMI for age Z-scores and age-adjusted LS-BMD and LS-BMAD Z-scores was analyzed.

RESULTS

For the statistical analysis, the DXA scans of 1799 non-Hispanic White children (823 females), of 1696 non-Hispanic Black children (817 females), and of 1839 Mexican American children (884 females) were eligible. The statistical analysis showed that taller and heavier children had significantly (p < 0.001) higher age-adjusted LS-BMD Z-scores than shorter and lighter children. But on LS-BMAD, only BMI and not height had a significant influence.

CONCLUSIONS

LS-BMD results in children were influenced significantly by their height and BMI, the LS-BMAD results were only influenced by their BMI. For the first time, the proposed method adjusts LS-BMD and LS-BMAD to BMI. An adjustment of the LS-BMD and LS-BMAD results to these factors might improve the clinical significance of an individual result.

Tracking of bone mass from childhood to puberty: a 7-year follow-up. The CHAMPS study DK

Bone mass in childhood is highly influenced by puberty. At the same age, bone mass was higher for pubertal than pre-pubertal children. A high level of tracking during 7 years from childhood through puberty was shown, indicating that early levels of bone mass may be important for later bone health.

INTRODUCTION

Bone mass development in childhood varies by sex and age, but also by pubertal stage. The objectives of this study were to (1) describe bone mass development in childhood as it relates to pubertal onset and to (2) determine the degree of tracking from childhood to adolescence.

METHODS

A longitudinal study with 7 years of follow-up was initiated in 2008 to include 831 children (407 boys) aged 8 to 17 years. Participants underwent whole body dual-energy X-ray absorptiometry (DXA) scanning, blood collection to quantify luteinizing hormone levels, and Tanner stage self-assessment three times during the 7-year follow-up. Total body less head bone mineral content, areal bone mineral density, and bone area were used to describe development in bone accrual and to examine tracking over 7 years.

RESULTS

Bone mass in pubertal children is higher than that of pre-pubertal children at the same age. Analysing tracking with quintiles of bone mass Z-scores in 2008 and 2015 showed that more than 80% of participants remained in the same or neighbouring quintile over the study period. Tracking was confirmed by correlation coefficients between Z-scores at baseline and 7-year follow-up (range, 0.80-0.84).

CONCLUSIONS

Bone mass is highly influenced by pubertal onset, and pubertal stage should be considered when examining children's bone health. Because bone mass indices track from childhood into puberty, children with low bone mass may be at risk of developing osteoporosis later in life.

Birth size, body composition, and adrenal androgens as determinants of bone mineral density in mid-childhood

BackgroundBirth weight has an impact on adult bone mass. Higher birth weight is associated with greater bone mineral content (BMC) and children born small for gestational age (SGA) are at an increased risk for impaired accrual of bone mass. Our aim was to study whether the impact of birth size or early childhood growth on bone mass is visible already in mid-childhood.MethodsWe studied 49 children born large for gestational age (LGA), 56 children born appropriate for gestational age (AGA), and 23 children born SGA at 5.0-8.7 years of age. Body composition was assessed by whole-body dual-energy X-ray absorptiometry. Fasting blood samples and anthropometric data were collected.ResultsThe children born SGA had lower bone mineral density (BMD) Z-score (P<0.001) and age- and sex-adjusted BMD (P<0.005) than the LGA and AGA children. Adjusted BMC, muscle mass, and body fat percentage (%BF) did not differ between the study groups. Muscle mass, BMI SD score (SDS), %BF, and serum dehydroepiandrosterone sulfate (DHEAS) concentration were the strongest predictors of high BMD in mid-childhood.ConclusionSGA-born children had lower BMD in mid-childhood compared with AGA- and LGA-born ones. Muscle mass or BMI SDS, %BF, and DHEAS were significant predictors of childhood BMD.

Body fat mass, lean body mass and associated biomarkers as determinants of bone mineral density in children 6-8years of age - The Physical Activity and Nutrition in Children (PANIC) study

Lean body mass (LM) has been positively associated with bone mineral density (BMD) in children and adolescents, but the relationship between body fat mass (FM) and BMD remains controversial. Several biomarkers secreted by adipose tissue, skeletal muscle, or bone may affect bone metabolism and BMD. We investigated the associations of LM, FM, and such biomarkers with BMD in children. We studied a population sample of 472 prepubertal Finnish children (227 girls, 245 boys) aged 6-8years. We assessed BMD, LM, and FM using whole-body dual-energy x-ray absorptiometry and analysed several biomarkers from fasting blood samples. We studied the associations of LM, FM, and the biomarkers with BMD of the whole body excluding the head using linear regression analysis. LM (standardized regression coefficient β=0.708, p<0.001), FM (β=0.358, p<0.001), and irisin (β=0.079, p=0.048) were positive correlates for BMD adjusted for age, sex, and height in all children. These associations remained statistically significant after further adjustment for LM or FM. The positive associations of dehydroepiandrosterone sulphate (DHEAS), insulin, homeostatic model assessment for insulin resistance (HOMA-IR), leptin, free leptin index, and high-sensitivity C-reactive protein and the negative association of leptin receptor with BMD were explained by FM. The positive associations of DHEAS and HOMA-IR with BMD were also explained by LM. Serum 25-hydroxyvitamin D was a positive correlate for BMD adjusted for age, sex, and height and after further adjustment for FM but not for LM. LM and FM were positive correlates for BMD also in girls and boys separately. In girls, insulin, HOMA-IR, leptin, and free leptin index were positively and leptin receptor was negatively associated with BMD adjusted for age, height, and LM. After adjustment for age, height, and FM, none of the biomarkers was associated with BMD. In boys, leptin and free leptin index were positively and leptin receptor was negatively associated with BMD adjusted for age, height, and LM. After adjustment for age, height and FM, 25(OH)D was positively and IGF-1 and leptin were negatively associated with BMD. FM strongly modified the association between leptin and BMD. LM but also FM were strong, independent positive correlates for BMD in all children, girls, and boys. Irisin was positively and independently associated with BMD in all children. The associations of other biomarkers with BMD were explained by LM or FM.

Fat mass is positively associated with bone mass acquisition in children with small or normal lean mass: A three-year follow-up study

The independent impact of fat mass (FM) on bone health is difficult to assess, as FM is correlated with lean soft tissue mass (LSTM). In a previous cross-sectional study, FM was suggested to help promote high bone mass acquisition in adolescents with small LSTM. The present prospective cohort study investigated the effects of FM on bone in pubertal children after stratification by height-normalized index of LSTM (LSTMI). The source population was all 5th grade children enrolled in either one of the two public elementary schools in Hamamatsu, Japan. Of these, 545 children who participated in both baseline (at age 11) and follow-up (at age 14) surveys were included in the present analysis. Body composition and whole body areal bone mineral density (aBMD) were measured using dual-energy X-ray absorptiometry. From baseline to follow-up, significant (P<0.05) differences were observed in changes in aBMD among tertiles of change in FM in both sexes after adjusting for confounding factors including LSTMI. After stratification by tertiles of sex-specific LSTMI, adjusted means of changes in aBMD according to tertiles of change in FM within the lowest and second lowest tertiles of LSTMI in both sexes showed a significant increase from the lower tertiles to the highest tertile of change in FM. In the highest tertile of LSTMI, changes in FM showed no significant association with changes in aBMD. These findings suggest that adipose tissue might help promote high bone mass acquisition in pubertal children with small or normal LSTMI.

Association between Anthropometric Indices, Body Composition and Bone Parameters in Thai Female Adolescents

OBJECTIVE

To investigate correlations between anthropometrics and body composition with bone parameters of the whole-body and lumbar spine in non-obese and obese Thai female adolescents.

METHODS

This study was performed in 135 female adolescents aged 15 to 18 y enrolled in secondary schools in southern Thailand. Subjects were grouped into non-obesity (underweight and normal-to-overweight) (BMI < 25) and obesity (BMI ≥ 25) groups. Anthropometric indices for obesity [body weight (BW), waist circumference (WC), and body mass index (BMI)] were recorded. Bone parameters (BMC, BMD, and Z-scores) of the whole-body and lumbar spine (L1-L4) and body composition (LBM, BFM, %fat, %lean, and %bone) were assessed by dual-energy X-ray absorptiometry (DXA). Correlations between anthropometrics, body composition, and bone parameters were evaluated and compared between subject groups.

RESULTS

The obesity group had significantly higher means of whole-body BMD, BMC and Z-score than non-obese group (p < 0.05). BMI and BW were positively associated with BFM and %fat (p < 0.05) for non-obese subjects. Obese subjects had greater lumbar spine BMC compared to non-obese subjects. BFM was correlated with whole-body BMC in obese group. BW was a positive determinant of BMC at both sites in all subject groups, particularly for obese subjects; BW had positive associations with all bone parameters at the lumbar spine.

CONCLUSIONS

BW can be used as a determinant of all bone parameters at lumbar spine, and BFM had a positive effect on whole-body BMC in Thai obese female adolescent subjects.

The Impact of Fat and Obesity on Bone Microarchitecture and Strength in Children

A complex interplay of genetic, environmental, hormonal, and behavioral factors affect skeletal development, several of which are associated with childhood fractures. Given the rise in obesity worldwide, it is of particular concern that excess fat accumulation during childhood appears to be a risk factor for fractures. Plausible explanations for this higher fracture risk include a greater propensity for falls, greater force generation upon fall impact, unhealthy lifestyle habits, and excessive adipose tissue that may have direct or indirect detrimental effects on skeletal development. To date, there remains little resolution or agreement about the impact of obesity and adiposity on skeletal development as well as the mechanisms underpinning these changes. Limitations of imaging modalities, short duration of follow-up in longitudinal studies, and differences among cohorts examined may all contribute to conflicting results. Nonetheless, a linear relationship between increasing adiposity and skeletal development seems unlikely. Fat mass may confer advantages to the developing cortical and trabecular bone compartments, provided that gains in fat mass are not excessive. However, when fat mass accumulation reaches excessive levels, unfavorable metabolic changes may impede skeletal development. Mechanisms underpinning these changes may relate to changes in the hormonal milieu, with adipokines potentially playing a central role, but again findings have been confounding. Changes in the relationship between fat and bone also appear to be age and sex dependent. Clearly, more work is needed to better understand the controversial impact of fat and obesity on skeletal development and fracture risk during childhood.

Vitamin D status of Icelandic children and its influence on bone accrual

The importance of vitamin D for children's bone health has been well established, but the effects of less severe deficiency are not fully known. The main objective of this study was to assess the vitamin D status of Icelandic children at the age of 7, and again at 9 years of age, and the association of vitamin D status with bone mineral content and bone accrual over 2 years. We invited 321 children to participate in this study, and 267 (83 %) took part; 211 (79 %) underwent a DXA scan and 164 were again scanned 2 years later; 159 (60 %) vitamin D samples were measured and 119 (75 %) were measured again 2 years later. At age 7, 65 % of the children had vitamin D concentrations <50 nmol/l, and at age 9 this figure was 60 %. At age 7, 43 % of the children had insufficient amounts of vitamin D (37.5-50 nmol/l), and 22 % had a vitamin D deficiency (<37.5 nmol/l). In linear regression analysis, no association was found between vitamin D and bone mineral content. Furthermore, there was no significant difference in bone accrual over 2 years for the children with insufficient or deficient vitamin D at both ages, compared to those having more than 50 nmol/l at both time points. More than 60 % of Icelandic children have inadequate concentrations of vitamin D in serum repeatedly over a 2-year interval. However, vitamin D in the range did not have a significant effect on bone mineral content or accrual at ages 7 and 9.

Chronic Psychosocial Stress Impairs Bone Homeostasis: A Study in the Social Isolation Reared Rat

Chronic psychosocial stress is a key player in the onset and aggravation of mental diseases, including psychosis. Although a strong association between this psychiatric condition and other medical co-morbidities has been recently demonstrated, few data on the link between psychosis and bone homeostasis are actually available. The aim of this study was to investigate whether chronic psychosocial stress induced by 4 or 7 weeks of social isolation in drug-naïve male Wistar rats could alter bone homeostasis in terms of bone thickness, mineral density and content, as well as markers of bone formation and resorption (sclerostin, cathepsin K, and CTX-I). We found that bone mineral density was increased in rats exposed to 7 weeks of social isolation, while no differences were detected in bone mineral content and area. Moreover, 7 weeks of social isolation lead to increase of femur thickness with respect to controls, suggesting the development of a hyperostosis condition. Isolated rats showed no changes in sclerostin levels, a marker of bone formation, compared to grouped animals. Conversely, bone resorption markers were significantly altered after 7 weeks of social isolation in terms of decrease in cathepsin K and increase of CTX-I. No alterations were found after 4 weeks of isolation rearing. Our observations suggest that chronic psychosocial stress might affect bone homeostasis, more likely independently from drug treatment. Thus, the social isolation model might help to identify possible new therapeutic targets to treat the burden of chronic psychosocial stress and to attempt alternative therapy choices.

Body mass but not vitamin D status is associated with bone mineral content and density in young school children in northern Sweden

Background

High latitude of residence where sun exposure is limited affects vitamin D status. Although vitamin D levels have been associated with poor bone health, cut-off values for optimising bone health are yet to be decided.

Objective

To assess vitamin D intake and status among young school children living at latitude 63–64 °N, in northern Sweden and to examine the association between vitamin D status and bone mineral content (BMC) and bone mineral density (BMD).

Design

In a cross-sectional study, diet was assessed by a 4-day food diary and a food frequency questionnaire in 8- to 9-year-old children (n=120). Energy, vitamin D, and calcium intakes were calculated. Physical activity was assessed using a pedometer for 7 days. Serum 25-hydroxyvitamin D (S-25[OH]D) levels were analysed by high-pressure liquid chromatography-atmospheric pressure chemical ionisation-mass spectrometry (n=113). BMC and BMD were assessed by dual energy X-ray absorptiometry scan. Height and weight were measured by standard procedures and BMI z-score was calculated using WHO AnthroPlus programme.

Results

The majority of children, 91%, did not reach the recommended vitamin D intake of 7.5 µg/day and 50% had insufficient S-25[OH]D levels defined as <50 nmol/l. The highest concentrations of S-25[OH]D were observed during the summer months (p=0.01). Body mass (p<0.01) but not S-25[OH]D was associated with measures of BMC and BMD. Furthermore, boys had higher total BMC (p=0.01), total body less head BMC (p=0.02), fat free mass (p<0.01), and a higher degree of physical activity (p=0.01) compared to girls.

Conclusions

Body mass was related to BMC and BMD measures in a population of prepubertal school children living at high latitudes in Sweden. Despite insufficient S-25[OH]D levels and low vitamin D intake, this did not appear to affect bone parameters. Prospective studies with repeated assessment of vitamin D status are needed to examine cut-off values for optimising bone health.

Leisure time computer use and adolescent bone health--findings from the Tromsø Study, Fit Futures: a cross-sectional study

OBJECTIVES

Low levels of physical activity may have considerable negative effects on bone health in adolescence, and increasing screen time in place of sporting activity during growth is worrying. This study explored the associations between self-reported screen time at weekends and bone mineral density (BMD).

DESIGN

In 2010/2011, 1038 (93%) of the region's first-year upper-secondary school students (15-18 years) attended the Tromsø Study, Fit Futures 1 (FF1). A follow-up survey (FF2) took place in 2012/2013. BMD at total hip, femoral neck and total body was measured as g/cm(²) by dual X-ray absorptiometry (GE Lunar prodigy). Lifestyle variables were self-reported, including questions on hours per day spent in front of television/computer during weekends and hours spent on leisure time physical activities. Complete data sets for 388/312 girls and 359/231 boys at FF1/FF2, respectively, were used in analyses. Sex stratified multiple regression analyses were performed.

RESULTS

Many adolescents balanced 2-4 h screen time with moderate or high physical activity levels. Screen time was positively related to body mass index (BMI) in boys (p=0.002), who spent more time in front of the computer than girls did (p<0.001). In boys, screen time was adversely associated with BMDFF1 at all sites, and these associations remained robust to adjustments for age, puberty, height, BMI, physical activity, vitamin D levels, smoking, alcohol, calcium and carbonated drink consumption (p<0.05). Screen time was also negatively associated with total hip BMD(FF2) (p=0.031). In contrast, girls who spent 4-6 h in front of the computer had higher BMD than the reference (<2 h).

CONCLUSIONS

In Norwegian boys, time spent on screen-based sedentary activity was negatively associated with BMD levels; this relationship persisted 2 years later. Such negative associations were not present among girls. Whether this surprising result is explained by biological differences remains unclear.