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.     

A 4-year follow-up study of the effects of calcium supplementation on bone density in elderly postmenopausal women

To determine the long-term effect of calcium supplementation on bone density, 84 elderly women (54–74 years) more than 10 years past the menopause were studied for 4 years as part of a follow-up study of a randomized, double-masked, placebo-controlled trial. The placebo group who did not take calcium supplements at all during the 4-year study (control group,n=21) served as a comparison with the treated group who took calcium supplements for 4 years (calcium supplement group,n=14). We also studied subjects who were treated for 2 years with calcium supplements and then ceased taking them (non-compliant group,n=49). The changes in bone density at the lumbar spine, hip and ankle sites, current calcium intake and activity were monitored. Over the 4 years the calcium supplement group (mean calcium intake 1988±90 mg/day) did not lose bone at the hip and ankle site. The control group (mean calcium intake 952±109 mg/day) lost significantly more bone than the calcium supplement group at all sites of the hip and ankle. No overall bone loss was seen at the spine, in either group, over the 4 years of this study. Between years 2 and 4 the non-compliant group (mean calcium intake 981±75 mg/day) lost significantly more bone at all sites of the ankle than the calcium supplement group. Therefore, calcium supplementation produces a sustained reduction in the rate of loss of bone density at the ankle and hip sites in elderly postmenopausal women. Increasing dietary calcium intake in women should be the aim of a public health campaign.     

Skeletal status in adolescents with end-stage renal failure: a longitudinal study

In a longitudinal study, bone status was assessed in adolescents and young adults aged 15.3±3.4 years at the onset of the study with end-stage renal failure (ESRF). The group consisted of 18 subjects (11 females and seven males), of whom nine patients were on hemodialysis and nine patients on peritoneal dialysis. Six patients were previous or current glucocorticoid (GCS) users. Renal failure was recognized before 6.1±4.1 years, and dialysis was performed for 3.0±2.0 years. Follow-up took placed 8.6±0.8 and 21.7±2.5 months later, and the following data were collected: bone mineral density (BMD) at the spine (s-BMD) and total body (TB-BMD) using DPX-L (Lunar, USA); quantitative ultrasound by DBM 1200 (IGEA, Italy) at the hand phalanges (Amplitude-dependent Speed of Sound, Ad-SoS), serum concentration of i-PTH, total calcium, ionized calcium and phosphate. Tanner stages were also evaluated. The mean values of BMD measurements and Ad-SoS were stable during a period of observation, and a mean Z-score for TB-BMD was significantly lower at the third versus baseline value (–1.87±1.75 versus –1.49±1.53, P<0.05). Z-scores for s-BMD and Ad-SoS decreased non-significantly. Changes in s-BMD and TB-BMD Z-scores were influenced by changes in body size and changes in biochemical parameters, and a change in Ad-SoS Z-score was not dependent on these factors. The values of second (P<0.05) and third (P<0.01) s-BMD Z-score were significantly lower in GCS treated subjects, and longitudinal change in spine Z-score was greater in GCS treated patients versus others (P<0.05). Duration of ESRF, duration and type of dialysis and gender did not influence skeletal variables. Skeletal measurements correlated significantly with Tanner stages (besides the correlation with Ad-SoS in the first measurement, r ranged from 0.5 to 0.72, P<0.05), and changes in Tanner stages observed over a period of observation did not correlate with changes in skeletal variables. Among laboratory variables, the following non-significant tendencies to change were observed: serum concentration of i-PTH and phosphate increased, and total and ionized calcium decreased. In conclusion, adolescent subjects with ESRF treated with dialysis showed stable mean values of skeletal measurements, and these were expressed as Z-scores, a tendency to drop was observed. The lack of an increase observed in normal healthy subjects of the same age, and low values in Z-scores, indicates that skeletal status is seriously affected in subjects with ESRF.     

Bone mineral density in live related kidney transplant children and adolescents

Successful kidney transplantation corrects many of the metabolic abnormalities associated with development of renal osteodystrophy, but despite a well-functioning graft, osteopenia, remains prevalent in adult and pediatric kidney recipients. The factors that affect the bone mineral density (BMD) and the long term course of BMD after transplantation in children is still unknown. We performed a cross sectional study to determine BMD in 83 recipients who received living renal allotransplants in Mansoura Urology & Nephrology Center between 1981 and 2002 (mean age at transplantation 13.2 ± 3.1 years) by dual energy x-ray absorptiometry at various time intervals up to 16 years after transplantation (mean duration after transplantation was 48 ± 34 months, range 12–192 months). The mean ± SD for BMD was −2.28 ± 2.06 for lumbar 2-4 spine and −1.44 ± 1.44 for the total body BMD as corrected for body surface area. Osteopenia/osteoporosis were present in about two thirds of our kidney transplant recipients. The significant risk factors for osteopenia/osteoprosis using univariate analysis were the cyclosporine based immunosuppressive regimen, cumulative dose of steroids/m² surface area, graft dysfunction and the urinary deoxypyridinoline. Using logistic regression analysis the cumulative steroid dose/m² surface area and the urinary deoxypyridinoline were the major significant predictors for bone loss. In conclusion, osteopenia and osteoprosis are common in pediatric and adolescent renal transplant patients. The cumulative steroid dose and the urinary deoxypyridinoline were the major predictors for bone loss. This revised version was published online in August 2006 with corrections to the Cover Date.     

Progressive vertebral deformities despite unchanged bone mineral density in patients with sarcoidosis: a 4-year follow-up study

Summary To evaluate the incidence of new and/or progressive vertebral deformities and changes in bone mineral density, we re-examined 66 patients with sarcoidosis after a follow-up period of four years. In 17 subjects (26%) new and/or progressive vertebral deformities were found, though BMD did not change significantly. Introduction Previous studies from our group have shown that morphometric vertebral deformities suggestive of fractures can be found in 20% of patients with sarcoidosis, despite a normal bone mineral density (BMD). The aim of this study was to determine the incidence of new and/or progressive vertebral deformities and the evolution of BMD during the course of this disease. Methods BMD of the hip (DXA) and vertebral fracture assessment (VFA) with lateral single energy densitometry was performed at baseline and after 45 months in 66 patients with sarcoidosis. Potential predictors of new/progressive vertebral deformities were assessed using logistic regression analysis. Results The BMD of the total group was unchanged after follow-up. The prevalence of vertebral deformities increased from 20 to 32% (p < 0.05); in 17 subjects (26%) new or progressive vertebral deformities were diagnosed. A lower T-score of the femoral neck [(OR = 2.5 (CI: 1.0-5.9), p < 0.05)] and mother with a hip fracture [(OR = 14.1 (CI:1.4-142.6), p < 0.05)] were independent predictors of new/progressive deformities. Conclusions In subjects with sarcoidosis the number of vertebral deformities increases in the course of this disease, despite unchanged BMD. The combination of low normal BMD and family history of fragility fractures confers an increased risk of the incidence of these deformities.     

Deficits in Bone Mineral Content in Children and Adolescents With Cystic Fibrosis Are Related to Height Deficits

Despite reports of decreased bone density, children with mild to moderate cystic fibrosis (CF)–associated pulmonary disease do not have increased fracture rates. Short stature and delayed puberty complicate interpretations of bone mineral status in many children with chronic diseases. This study sought to characterize bone mineral content (BMC) in children with CF and determine its relationship to growth, body composition, and disease severity. Dual-energy X-ray absorptiometry measurements of whole body BMC (WB-BMC), spine BMC (Sp-BMC), and lean body mass (LBM) were converted to Z-scores in 82 CF and 322 healthy children. Effects of growth, body composition, and CF-disease characteristics on BMC were determined using linear regression. Children with CF had lower weight, height (HT), BMI, and LBM-Z. Females with CF had lower (p < 0.001) WB-BMC-Z (−1.1 ± 1.1) and Sp-BMC-Z (−0.9 ± 1.1) than controls. Following adjustment for height standard deviation score (HT-Z), deficits were absent. Males with CF had lower (p < 0.001) WB-BMC-Z (−1.3 ± 0.9) and Sp-BMC-Z (−0.9 ± 1.3). Following adjustment for HT-Z, WB-BMC-Z deficits were attenuated and Sp-BMC-Z deficits absent. HT-Z, LBM-Z, and pulmonary function had independent effects on WB-BMC-Z and Sp-BMC-Z. BMC deficits are related to altered body size, reduced LBM, and pulmonary function in children with CF. Interventions targeting improved growth, muscle mass, and pulmonary function may benefit bone health in CF.     

A cross-sectional study of bone mineral density in children and adolescents attending a Cystic Fibrosis Centre

BackgroundLow bone mineral density is common in adults with cystic fibrosis. Children with good lung function compared to controls matched for body size have normal bone mineralisation. There are few data in large unselected populations of children.MethodsAll children between five and 16 years were invited to take part. Disease severity was assessed. Bone mineral measurements using a GE-Lunar Prodigy densitometer were expressed as age and gender matched Z-scores. Bone mineral apparent density for L2–L4 was estimated and data from UK Caucasian children used to create age and gender specific reference ranges for predicted values. Z-scores were calculated. Total body analysis utilised the Molgaard method. Blood was sampled for measurement of 25-hydroxyvitamin D, and parathyroid hormone levels.Results107 children entered the study. 18 and 10 children had low areal and apparent bone mineral density respectively. Short, narrow bones were common. Fifteen children reported 22 fractures, 20 with associated trauma. The best predictors of bone status were ZBMI and percent predicted FEV₁.ConclusionsBone mineral density corrected for body size was normal in over 90% of children. These results are similar to previously reported results in small studies of children with well preserved respiratory function.     

789例正常儿童骨密度与奶制品、维生素A、D的关系

为了解北京市儿童骨密度及与常见营养因素：奶制品，维生素A、D的关系，用单光子吸收测量法，测量了789例2～8岁正常儿童骨密度。统计学结果显示：儿童骨密度与年龄成正相关，7岁时出现骨密度增长高峰。骨密度低于平均值减一个标准差占受检总数的11．4%。不同年龄儿童分组l检验结果显示：奶制品 维生素A、D组儿童骨密度最高，奶制品组次之，非奶制品 非维生素A、D组骨密度最低。提示服用奶制品及维生素A、D，对儿童骨胳的正常发育及骨质疏松症早期预防有十分重要的意义。     

Controlled longitudinal study of bone mass accrual in children and adolescents with cystic fibrosis

BACKGROUND: A study was undertaken to observe the gains in bone mass in children and adolescents with cystic fibrosis (CF) over 24 months and to examine the relationship between areal bone mineral density (aBMD) and associated clinical parameters including physical activity, nutrition, and 25-hydroxyvitamin D (25OHD). METHODS: Areal BMD of the total body (TB), lumbar spine (LS), and total femoral neck (FNt) were repeatedly measured in 85 subjects aged 5-18 years with CF and 100 age and sex matched controls over 2 years. At each visit anthropometric variables, nutritional parameters, pubertal status, disease severity, physical activity, dietary calcium, caloric intake, and serum 25OHD were assessed and related to aBMD. RESULTS: After adjusting for age, sex, and height Z-score, gains in LS aBMD in children (5-10 years) and TB and FNt aBMD in adolescents (11-18 years) with CF were significantly less than in controls. Lean tissue mass was significantly associated with TB and LS aBMD gains in children and adolescents and explained a significant proportion of the aBMD deficit observed. Lung function parameters were significantly associated with aBMD gains in adolescents with CF. CONCLUSIONS: Inadequate bone mass accrual during childhood and adolescence contributes to the low bone mass observed in adults with CF. Accounting for the height discrepancy which is frequently observed in those with CF, in addition to age and sex, is important when assessing low bone mass in children and adolescents with CF. To optimise an individual's potential to acquire maximal bone mass, it is necessary to maximise nutritional status and limit the progression of chronic suppurative lung disease.     

Dancing for bone health: a 3-year longitudinal study of bone mineral accrual across puberty in female non-elite dancers and controls

Introduction Weight-bearing exercise during growth enhances peak bone mass. However, the window of opportunity for optimizing positive effects of exercise on peak bone mass remains to be fully defined. Ballet dancing provides a model of mechanical loading patterns required to site-specifically modulate bone. Methods We assessed the effects of ballet dancing on bone mineral accrual in female non-elite dancers and normally active controls for 3 years across puberty. We recruited 82 ballet dancers and 61 controls age 8–11 years at baseline. Participants were measured over 3 consecutive years; however, the overlap in ages allowed analysis of the groups across 8–14 years of age. We annually assessed bone mineral content (BMC) at the total body (TB), including upper and lower limb regions, and biannually assessed BMC at the proximal femur and lumbar spine (LS) using dual x-ray absorptiometry (DXA). We derived TB lean mass and fat mass from DXA TB scans. Anthropometry, exercise levels, and calcium intake were also measured biannually. Maturational age was determined by age at peak height velocity (PHV). A multilevel regression model was used to determine the independent effects of body size, body composition, maturation, exercise levels, and calcium intake at each measurement occasion. Results When adjusted for growth and maturation, dancers had significantly greater BMC at the TB, lower limbs, femoral neck (FN), and LS than controls. Excepting the FN region, these differences became apparent at 1 year post-PHV, or the peripubertal years, and by 2 years post-PHV the differences represented a cumulative advantage in dancers of 0.6–1.3% (p<0.05) greater BMC than controls. At the FN, dancers had 4% (p<0.05) greater BMC than controls in prepuberty and maintained this advantage throughout the pubertal years. Conclusions Results from this novel population provide evidence for modest site-specific and maturity-specific effects of mechanical loading on bone.     

Bone mineral density and risk factors for osteoporosis—A population-based study of 1600 perimenopausal women

Population-based epidemiological studies on osteoporosis are few. Our study evaluated the effects of menopause and certain putative behavioral risk factors on bone mineral density (BMD). Spinal and femoral neck BMD were measured with dual X-ray absorptiometry (DXA) from 1600 perimenopausal women aged 48–59 years (mean 53.2 years) with no diseases or medications known to affect bone metabolism. These women were a selected sample of the Kuopio Osteoporosis Risk Factor and Prevention Study population (n=14,220). There was a wide variation of BMD among perimenopausal women. Menopause had a major effect on BMD. Postmenopausal women had significantly lower BMD in both spine (-6.2%) and femoral neck (-3.9%) as compared with premenopausal women. Multiple regression analysis showed that weight, menopausal status, age, and grip strength were significant independent predictors of both spinal and femoral BMD. Additionally, physical activity was found to be a significant predictor of femoral BMD, and alcohol consumption was a significant predictor of spinal BMD. However, current anthropometric and lifestyle factors explained only 18.7–25.4% of the variability of BMD. Therefore, the estimation of the risk factor status at menopause is not an adequate substitute for bone densitometry. However, our results may in part help clinicians to identify the risk groups at which to direct bone density measurements.     

Shorter Sleep may be a Risk Factor for Impaired Bone Mass Accrual in Childhood

The purpose of the study was to investigate whether sleep duration during early childhood was associated with fat mass and bone mineral content (BMC). BMC and fat mass were measured by dual-energy X-ray absorptiometry in children (n = 336) aged 4–12 yr. Sleep was quantified according to parental report of hours slept at night and napping. The relationship between sleep pattern and body composition was tested using analysis of variance including confounding factors. Based on the sample distribution, children were grouped into tertiles of sleep duration. BMC was greater in children with longer sleep duration (p = 0.02). Age was inversely associated with sleep duration; therefore, the sample was analyzed by age category using age 7 yr as a cut-off point. The relationship remained significant only among younger children. Napping was positively associated with BMC (p = 0.001). Sleep duration was not associated with fat parameters. Longer sleep duration may allow for optimal energy resource partitioning in which bone is favored. Sleep duration of less than 8 h may impair bone mass accrual, particularly during periods of rapid growth.     

Effects of pubertal development, height, weight, and grip strength on the bone mineral density of the lumbar spine and hip in peripubertal Japanese children: Kyoto kids increase density in the skeleton study (Kyoto KIDS study)

The effects of growth and pubertal development on the bone mineral density (BMD) of the lumbar spine and hip in peripubertal Japanese children were studied as a basis for evaluating the effects of modifiable factors on bone mass gain. The study comprised bone mass measurements in the lumbar spine (L2–4), femoral neck, and total hip using dual-energy X-ray absorptiometry as well as body size measurements and detailed interviews on medical history and pubertal status. The subjects were 404 first-grade students in three junior high schools (129 boys and 275 girls, mean age 12.8 ± 0.3 years) with no diseases or medication that would affect bone metabolism. BMD at each site showed an increasing trend with physical growth and sexual maturity. Significant positive correlations were observed between BMD at every skeletal site and height, weight, and grip strength in pre- and postpubertal boys and girls. In multiple regression analyses, pubertal development had a significant positive independent effect on BMD at every skeletal site in girls, but not in boys. Physical and pubertal development showed major effects on BMD, but the magnitude of these effects differed in boys and girls, even if they were of the same age. We conclude that confounding factors due to physical and pubertal development should be taken into consideration in different ways for boys and girls in investigations on the effects of environmental or behavioral factors on bone mass acquisition in peripubertal children.     

Changes in Bone Mass,Bone Structure,Bone Biomechanical Properties,and Bone Metabolism after Spinal Cord Injury: A 6-Month Longitudinal Study in Growing Rats

Spinal cord injury (SCI) results in a great decline in bone mineral density (BMD) and deterioration of bone microarchitecture. The objective of this study was to investigate the time course of the changes in BMD, microarchitecture, biomechanical properties, and bone turnover in male growing rats following SCI. Sixty male growing Sprague-Dawley rats, 6 weeks of age, were randomly divided into SCI (lower thoracic cord transection) and sham-operated groups, and bone tissues and blood samples were examined at 3 weeks, 6 weeks, and 6 months after surgery. SCI rats had low bone weight (wet, dry, and ash weight) and BMD of the femora, tibiae, and third lumbar vertebrae at all time points compared to sham rats, while in forelimbs, there was a decrease of dry and ash weight compared to sham rats only at 3 weeks but not BMD. Bone microarchitecture and trabecular connectivity were deteriorated in SCI rats and remained so after. Bone formation rate and serum osteocalcin level in SCI rats were significantly increased 3 weeks after SCI surgery. However, eroded surface/bone surface and serum N-terminal telopeptide of type I collagen level remained elevated from 3 weeks to 6 months. In addition, SCI rats showed poor biomechanical properties in the proximal tibiae and femora but not in the humeri. In conclusion, SCI causes profound BMD loss, disturbances in bone microarchitecture, decreased mechanical strength in the lower extremity and lumbar spine, and high bone turnover. These findings will allow better understanding of osteoporosis following SCI.     

Pattern of Periprosthetic Bone Remodeling Around Stable Uncemented Tapered Hip Stems: A prospective 84-month follow-up study and a Median 156-month Cross-Sectional Study with DXA

Bone resorption in the proximal femur is commonly seen after total hip arthroplasty (THA). With dual energy X-ray absorptiometry (DXA), the amount of bone mass (BMD) after implantation of a total hip stem can be precisely determined. However, prospective evaluation of the change of bone mass around the stem is only available for selected stems and short-term follow-up (up to 36 months). We analyzed BMD in patients who had undergone uncemented THA by DXA. Only patients with good clinical outcome (Merle d Aubigné score > 12) were included to obtain normative data for regular bone response. Two separate studies were performed: a prospective longitudinal study over 84 months with baseline values acquired within the first postoperative week (group A) (n = 26 patients) and a separate cross-sectional study, median follow-up 156 (124-178) months (group B) (n = 35 patients). Regions of interest were defined according to Gruen (ROI 1-7) and as net average ROI (net avg) for the periprosthetic femoral bone. After the initial remodeling process (12 months), BMD was compared to the 84-month (longitudinal) and the 156-month (cross-sectional) follow-up values to determine long-term periprosthetic changes of bone mineral density. The longitudinal study (group A), after the initial bone remodeling, showed no relevant further bone loss for women and men with BMD values 1.19 ± 0.15 and 1.40 ± 0.19, respectively, 12 months (women 89.8%, men 93.6%), and 1.19 ± 0.13 and 1.36 ± 0.18, respectively, after 84 months (women 90.0%, men 91.3%) (P = 0.98, P = 0.08,) respectively. The distribution of the BMD around the stem changed during the first 12 months. The ROIs around the proximal stem (ROI 1 and 7) showed the lowest absolute values at the 12-month follow-up and BMD in ROI 7 decreased most during the further follow-up until 84 months. The cross-sectional study (group B) showed no significant difference in BMD (net avg) values at a median of 156 months follow-up compared to the 12-month values (group A) (women: P = 0.77, men: P = 0.44). Initial BMD, implant diameter, and body mass index did not influence BMD loss (net avg) in this study, whereas age showed a weak correlation with BMD loss. The results show that after the initial remodeling process, no relevant further bone loss (net avg) occurs up to 84 months postsurgery, and values after a median of 156 months are similar. Normative long-term changes in the periprosthetic bone can be demonstrated in defined ROIs after implantation of a tapered corundum-blasted titanium stem with a good clinical result.     

Bone mineral density in diabetic children and adolescents: a follow-up study

OBJECTIVE: To establish whether T1DM can affect bone mineral density (BMD) in children and adolescents. RESEARCH DESIGN AND METHODS: We performed a cross-sectional and longitudinal study of 57 diabetic children and adolescents and 57 normal controls. Total body and lumbar BMD and bone mineral content (BMC) were assessed by DXA (Lunar DPX) and volumetric transformation was calculated using the Katzman formula for total body BMD (BMAD) and using the Kroger formula for Lumbar BMD (L2L4BMDvol). BMC, BMAD, BMDspine, and L2L4BMDvol were adjusted for confounding factors such as age, gender, BMI, height, weight, and pubertal stage. RESULTS: BMDspine in the control group increased by 0.006 (g/cm(2))/year; while in the 39 diabetic patients longitudinally studied, it dropped by 0.006 (g/cm(2))/year during a follow-up period of 51 +/- 27 months. The average time spent weekly doing physical activity resulted in T1DM group directly correlated to BCM (P < 0.001) and inversely correlated with BMDspine (P < 0.05) and L2L4BMDvol (P < 0.01). L2L4BMDvol resulted significantly correlated with previous BMD spine (R = 0.63; P < 0.0001) and BMC evaluation (R = 0.42; P < 0.01) but not with BMAD. A second lumbar DXA evaluation performed in 38 patients after 1.00 +/- 0.16 years confirmed a small but significant decrease of 1.6% per year in L2L4BMDvol. The percentage of variation of L2L4BMDvol between the two evaluations was not correlated with the level of metabolic control, insulin requirement, and duration of the disease. Patients with complications showed similar L2L4BMDvol to patients without complications. CONCLUSIONS: Diabetic children and adolescents show a slight negative pattern of spine mineralization, which does not depend on metabolic control and microvascular complications.     

Body mass index, percent body fat, and bone mass in a cohort of Chinese twins aged 6 to 18 years

Introduction This report examines the relationship of body mass index (BMI), percent body fat (%BF), and bone mass in a cohort of male and female twins recruited from Anhui province, China, ages 6–18 years—577 male pairs (mean age = 11.4) and 478 female pairs (mean age = 11.6). Methods Whole body bone mineral content (WBMC) in (g), whole body bone area (WBA) in (cm²), and %BF were measured using DEXA (Lunar Prodigy, USA). Regression analysis of within-pair differences was used to assess the strength of the association, and the analysis was stratified by gender and age group, where age cut-offs were based on ages at spermarche or menarche estimated from large population based studies in China. Males were stratified at ages before 14 and age 14–18, and females at ages prior to 12 and age 12–18. Results Univariately, BMI and %BF were associated with WBMC and WBA in the younger males and females, and in older males; %BF was significant only in older females. Multivariate models included both BMI and %BF. Among the younger males, age < 14, BMI and %BF were significantly associated with WBMC and WBA. In the younger females, age < 12, %BF was only significant to WBA. In the older age group, only BMI was significant to WBMC and WBA in females, but in males, BMI was positively associated, and %BF was negatively associated with both bone measures. Discussion These findings show that association between BMI and %BF and bone mass differ across gender and developmental stages, and %BF appears to be beneficial at younger ages, but detrimental or non-beneficial at older ages of development.     

Genetic and environmental determinants on bone loss in postmenopausal Caucasian women: a 14-year longitudinal twin study

Summary  This longitudinal twin study documented that genetic factors explain 44–56% of the between-individual variance in bone loss at femoral neck, lumbar spine, and forearm in postmenopausal Caucasian women, providing a rationale for identifying the specific genes involved. Introduction  Although there is a significant genetic effect on peak BMD, until recently, no substantive studies on heritability of bone loss in human were available. The aim of the study was to estimate the heritability of the bone loss at multiple sites in postmenopausal Caucasian women. Methods  Postmenopausal female monozygotic (MZ) and dizygotic (DZ) twins aged 40 or above at baseline were selected from the TwinsUK registry and followed up for an average of 8 years (range 5–14 years). All twins were noncurrent hormone replacement therapy users and not on any osteoporosis treatment. They had dual-energy X-ray absorptiometry (DXA) scans of their hip, lumbar spine, and forearm several times (range 2–9) during the follow-up period. Individual bone losses at femoral neck, lumbar spine, and forearm were estimated by linear regression modeling. Structural equation modeling was utilized to estimate the heritability of the bone loss. Results  A total of 712 postmenopausal Caucasian female twins (152 MZ and 204 DZ pairs) were included. MZ twins were older and had slightly lower BMD at all sites than DZ twins. DZ twins had slightly higher bone loss at lumbar spine, but similar at femoral neck and forearm compared to MZ twins. Intraclass correlation coefficients (ICC) for the bone loss at all sites were significantly higher in MZ than DZ twin pairs (p = 0.0045, 0.0003, and 0.0007 for femoral neck, lumbar spine, and forearm, respectively), indicating a significant genetic influence on bone loss at these sites. After adjustment for age at baseline and weight change during the follow-up, the heritability estimate was 47% (95% CI 27–63%) for bone loss at femoral neck, 44% (95% CI 27–58%) for lumbar spine, and 56% (95% CI 44–65%) for forearm. Conclusions  Our data suggest that up to 56% of the between-individual variance in bone loss is due to genes, providing a rationale to identify specific genetic factors for bone loss.     

Familial aggregation of bone mineral density and bone mineral content in a Chinese population

Familial aggregation of bone mineral density (BMD) and bone mineral content (BMC) has been shown in twin and familial studies, but most sample sizes were small. We here report a large familial aggregation study in a Chinese population. A total of 13,973 siblings aged 25–64 years from 3,882 families were enrolled from Anhui, China. We assessed the whole-body, hip and lumbar spine BMD and BMC by dual-energy X-ray absorptiometry (DXA). Intra-class correlation coefficients of BMD and BMC between siblings varied among different skeletal sites and between different age groups of male sib-pairs and premenopausal and postmenopausal female sib-pairs, with a range of 0.228 to 0.397. The sibling recurrence risk ratio (s) of osteoporosis was 2.6 in our population. We also evaluated the joint association of the BMD values of the first siblings and the second siblings with the risk of low BMD (defined as less than the 10th percentile of the same group population) of their younger siblings. If both the first and second siblings BMDs were in the lowest tertile, the odd ratios (ORs) of low BMD in their subsequent siblings were 8.32 [95% confidence interval (CI) 5.59–12.39)], 8.71 (95% CI 5.74–13.22) and 5.90 (95% CI 3.57–9.76) for total body, total hip and lumbar spine, respectively. This study demonstrates a significant familial aggregation of BMD and BMC in a large sample of rural Chinese adults.     

Changes in bone mineral density, body composition and biochemical markers of bone turnover during weight gain in adolescents with severe anorexia nervosa: a 1-year prospective study

Osteoporosis is a serious complication of anorexia nervosa and in affected adolescents may result in a permanent deficit in bone mass. The pathophysiology of this bone disease has not been clearly defined. In this prospective study of 26 young women with anorexia nervosa aged 13–20 years (mean 16.5) we have measured changes in bone mineral density, total body composition and biochemical indices of bone turnover over 1 year. Over this period there was a mean weight gain of 10 kg and significant height gain with baseline and final values for body mass index of 14.2±1.7 and 17.6±2.3 kg/m² (P<0.001). However, no significant changes were seen in bone mineral density in the spine or proximal femur during the study; total body bone mineral content was significantly higher than baseline at 3 months and 12 months (P=0.001 and P<0.0001), but total body bone mineral density at 3 months was significantly lower than baseline (P=0.003). Serum osteocalcin and bone-specific alkaline phosphatase values increased significantly and remained higher than baseline at all time points whereas urinary NTX/creatinine excretion showed a non-significant increase over the first 6 months of the study, but at 12 months, the mean value was significantly lower than baseline. Mean serum 25-hydroxyvitamin D levels showed a significant decrease at 6 months (P<0.05), but returned towards baseline thereafter. There was a significant increase in serum parathyroid hormone levels at all time points compared to baseline, these occurring within the normal range. These results indicate that although weight gain in young anorexics is associated with linear growth, bone mineral density does not increase. Whether this deficit can be corrected subsequently requires longer-term prospective studies.