Bone mineral density and body composition in boys with distal forearm fractures: a dual-energy x-ray absorptiometry study

The role of dietary calcium in bone health

Approximately 99% of body Ca is found in bone, where it serves a key structural role as a component of hydroxyapatite. Dietary requirements for Ca are determined by the needs for bone development and maintenance, which vary throughout the life stage, with greater needs during the periods of rapid growth in childhood and adolescence, during pregnancy and lactation, and in later life. There is considerable disagreement between expert groups on the daily Ca intake levels that should be recommended, reflecting the uncertainty in the data for establishing Ca requirements. Inadequate dietary Ca in early life impairs bone development, and Ca supplementation of the usual diet for periods of ≤3 years has been shown to enhance bone mineral status in children and adolescents. However, it is unclear whether this benefit is long term, leading to the optimisation of peak bone mass in early adulthood. In later years inadequate dietary Ca accelerates bone loss and may contribute to osteoporosis. Ca supplementation of the usual diet in post-menopausal women and older men has been shown to reduce the rate of loss of bone mineral density at a number of sites over periods of 1–2 years. However, the extent to which this outcome reduces fracture risk needs to be determined. Even allowing for disagreements on recommended intakes, evidence indicates that dietary Ca intake is inadequate for maintenance of bone health in a substantial proportion of some population groups, particularly adolescent girls and older women.

Fracture rate in children with cerebral palsy

OBJECTIVES

To determine the prevalence of previous fracture, the rate of fracture over time and associated risk factors for fracture in children with moderate or severe cerebral palsy (CP).

STUDY DESIGN

Three hundred and sixty-four children with moderate-to-severe motor impairment (Gross Motor Function Classification System III, IV and V) enrolled in a multi-centre, region-based longitudinal study of growth, nutrition and health. Of these, 297 had baseline fracture information and 261 children had at least one follow-up assessment. Median duration of follow-up was 1.6 years, for over 600 person-years of follow-up.

RESULTS

Forty-six (15.5%) children reported 62 previous fractures at baseline assessment. Children with a history of fractures at baseline were older (mean age 11.9 vs. 8.9 years, p<0.0001) and had greater body fat (triceps z-score -0.01 vs. -0.68, p=0.0003) than children with no previous fracture. Twenty children (6.7%) reported 24 fractures during the follow-up period. Factors associated with risk of fracture during the follow-up period were higher body fat (p=0.03), gastrostomy use (p=0.05) and previous fracture (p=0.10). Based on 24 fractures in 604.5 person-years of follow-up, the rate of fracture was 4.0 per hundred children (4.0%) per year. For children with a history of fracture at baseline, the fracture rate was 7.0% per year; for children with gastrostomy, 6.8% per year; and for children with high triceps skinfold, 9.7% per year.

CONCLUSIONS

Children with moderate or severe CP are at high risk for fracture. Children with greater body fat, feeding gastrostomy and prior history of fracture are at highest risk and may benefit most from intervention. Further longitudinal study and clinical trials in children with CP are needed to better understand the factors contributing to fracture risk in this population and the best methods of prevention and treatment.

DXA measurements confirm that parental perceptions of elevated adiposity in young children are poor

OBJECTIVE

To compare parental assessments of child body weight status with BMI measurements and determine whether children who are incorrectly classified differ in body composition from those whose parents correctly rate child weight. Also to ascertain whether children of obese parents differ from those of non-obese parents in actual or perceived body weight.

RESEARCH METHODS AND PROCEDURES

Weights, heights, BMI, and waist girths of New Zealand children ages 3 to 8 years were determined. Fat mass, fat percentage, and lean mass were measured by DXA (n = 96). Parents classified child weight status as underweight, normal-weight, slightly overweight, or overweight. Centers for Disease Control and Prevention 2000 percentiles of BMI were used.

RESULTS

Parents underestimated child weight status. Despite having 83% more fat mass than children with BMI values below the 85th percentile, only 7 of 31 children with BMI values at or above the 85th percentile were rated as slightly overweight or overweight. In the whole sample, participants whose weight status was underestimated by parents (40 of the 96 children) had l9% less fat mass but similar lean mass as children whose weight status was correctly classified. However, children of obese and non-obese parents did not differ in body composition or anthropometry, and obese parents did not underestimate child weight more than non-obese parents.

DISCUSSION

Because parents underestimate child weight, but BMI values at or above the 85th percentile identify high body fat well, advising parents of the BMI status of their children should improve strategies to prevent excessive fat gain in young children.

Incidence of skeletal complications during treatment of childhood acute lymphoblastic leukemia: comparison of fracture risk with the General Practice Research Database

BACKGROUND

Skeletal complications during or after treatment of acute lymphoblastic leukemia (ALL) have been frequently reported and can cause substantial morbidity, yet their incidence is not well established. The present study assessed the incidence of fractures, osteonecrosis (ON), and bone pain during ALL treatment and compared the fracture incidence with age- and sex-specific reference data from the UK General Practice Research Database (GPRD).

PROCEDURE

Medical records of 122 ALL patients diagnosed at our institution from 1992 to 2004 were reviewed for information on fractures, ON, bone pain, and their anatomical location, risk group, phase of antileukemic therapy, and time since diagnosis. Evaluation of skeletal complications was followed up until July 2005 or the patient's death. Thirteen children were excluded as they were transferred to other institutions shortly after diagnosis.

RESULTS

Skeletal complications occurred at a 5-year incidence of 32.7%. The 5-year incidence of fractures, ON, and isolated bone pain was 13.5%, 12.1%, and 12.3%, respectively. The relative rate of fractures adjusted for age and sex was 2.03 (95% confidence interval 1.15-3.57) compared to the GPRD, with greatest rates in children <5 years. Thirty ON occurred in 10 patients with a 15 times greater incidence in children >10 years than in those <5 years. Nearly all skeletal complications occurred during maintenance therapy at a median of 14.92 months (range 0.0-53.8) after diagnosis and in weight-bearing bones.

CONCLUSIONS

The doubled fracture rate and the high incidence of skeletal complications during the first years after diagnosis suggest the developing skeleton is very vulnerable in this period. Adolescents develop more ON whereas younger children may be more prone to fractures. Serious "immediate effects" of chemotherapy on bone appear of great concern and should entail preventative studies in this group of patients.

Assessing bone mass in children and adolescents

Growing awareness that osteoporosis may have its antecedents in childhood has led to increasing interest in assessing bone mass in children and adolescents. Several noninvasive imaging techniques are currently available to measure properties of the growing skeleton, including bone mass, density, cross-sectional area, and microarchitecture. Dual-energy x-ray absorptiometry (DXA) is the most widely used technique, but it has several major limitations associated with its dependence on two-dimensional projections. Quantitative CT and peripheral quantitative CT allow three-dimensional imaging but are more costly and have higher radiation exposure. Quantitative ultrasound is simple and inexpensive but can measure bone "quality" only at a single peripheral site. MRI techniques for measuring bone are still under development and not yet ready for clinical use. For all of these techniques, clinical interpretation of the bone measures obtained remains a significant challenge. Further research is needed to relate these measures to osteoporosis in the elderly and to short-term and long-term fracture risk.

Nutrition and bone growth and development

The growth and development of the human skeleton requires an adequate supply of many different nutritional factors. Classical nutrient deficiencies are associated with stunting (e.g. energy, protein, Zn), rickets (e.g. vitamin D) and other bone abnormalities (e.g. Cu, Zn, vitamin C). In recent years there has been interest in the role nutrition may play in bone growth at intakes above those required to prevent classical deficiencies, particularly in relation to optimising peak bone mass and minimising osteoporosis risk. There is evidence to suggest that peak bone mass and later fracture risk are influenced by the pattern of growth in childhood and by nutritional exposures in utero, in infancy and during childhood and adolescence. Of the individual nutrients, particular attention has been paid to Ca, vitamin D, protein and P. There has also been interest in several food groups, particularly dairy products, fruit and vegetables and foods contributing to acid-base balance. However, it is not possible at the present time to define dietary reference values using bone health as a criterion, and the question of what type of diet constitutes the best support for optimal bone growth and development remains open. Prudent recommendations (Department of Health, 1998; World Health Organization/Food and Agriculture Organization, 2003) are the same as those for adults, i.e. to consume a Ca intake close to the reference nutrient intake, optimise vitamin D status through adequate summer sunshine exposure (and diet supplementation where appropriate), be physically active, have a body weight in the healthy range, restrict salt intake and consume plenty of fruit and vegetables.

Mechanisms of disease: is osteoporosis the obesity of bone?

Osteoporosis and obesity, two disorders of body composition, are growing in prevalence. Interestingly, these diseases share several features including a genetic predisposition and a common progenitor cell. With aging, the composition of bone marrow shifts to favor the presence of adipocytes, osteoclast activity increases, and osteoblast function declines, resulting in osteoporosis. Secondary causes of osteoporosis, including diabetes mellitus, glucocorticoids and immobility, are associated with bone-marrow adiposity. In this review, we ask a provocative question: does fat infiltration in the bone marrow cause low bone mass or is it a result of bone loss? Unraveling the interface between bone and fat at a molecular and cellular level is likely to lead to a better understanding of several diseases, and to the development of drugs for both osteoporosis and obesity.

Effects of calcium supplementation on bone density in healthy children: meta-analysis of randomised controlled trials

OBJECTIVES

To assess the effectiveness of calcium supplementation for improving bone mineral density in healthy children and to determine if any effect is modified by other factors and persists after supplementation stops.

DESIGN

Meta-analysis.

DATA SOURCES

Electronic bibliographic databases, hand searching of conference proceedings, and contacting authors for unpublished data.

REVIEW METHODS

We included randomised placebo controlled trials of calcium supplementation in healthy children that lasted at least three months and had bone outcomes measured after at least six months of follow-up. Two reviewers independently extracted data and assessed quality. Meta-analyses predominantly used fixed effects models with outcomes given as standardised mean differences.

RESULTS

We included 19 studies involving 2859 children. Calcium supplementation had no effect on bone mineral density at the femoral neck or lumbar spine. There was a small effect on total body bone mineral content (standardised mean difference 0.14, 95% confidence interval 0.01 to 0.27) and upper limb bone mineral density (0.14, 0.04 to 0.24). This effect persisted after the end of supplementation only at the upper limb (0.14, 0.01 to 0.28). There was no evidence that sex, baseline calcium intake, pubertal stage, ethnicity, or level of physical activity modified the effect.

CONCLUSIONS

The small effect of calcium supplementation on bone mineral density in the upper limb is unlikely to reduce the risk of fracture, either in childhood or later life, to a degree of major public health importance.

Fractures and recurrent fractures in children; varying effects of environmental factors as well as bone size and mass

BACKGROUND

Fractures are frequent in childhood and cause considerable morbidity. Previous reports have indicated a variety of potential contributors to fracture risk including low bone mineral content and density, milk avoidance, lack of exercise, asthma, obesity, and a high consumption of carbonated beverages.

AIMS

We wished to test the hypothesis that children who sustain recurrent fractures have a lower bone mass and a higher prevalence of underlying risk factors for fracture than those who fracture once or not at all.

METHODS

We studied 150 children aged 4-16 years: 50 who had suffered recurrent fractures, 50 who had fractured for the first time, and 50 fracture-free controls. Subjects underwent assessment of bone size and mass by total body (TB) and lumbar spine (L2-4) dual energy X-ray absorptiometry (DXA). Values were adjusted for body size, based on the control group measurements as unadjusted DXA values are substantially influenced by size in children. Anthropometry and grip dynamometry were carried out, and information about factors implicated in fracture aetiology such as milk intake, physical activity levels, asthma prevalence and carbonated beverage consumption were recorded using questionnaires.

RESULTS

Children who had sustained one or more fractures had a significantly lower BMC and aBMD at all sites than controls after conversion to size adjusted z scores (L2-4 BMC P = 0.0002; L2-4 aBMD P < 0.0001; TB BMC P < 0.0001; TB aBMD P < 0.0001); estimates for TB excluded fracture sites. There was, however, no difference in adjusted bone mass between children with one and those with recurrent fractures. Children with recurrent fractures had a significantly lower milk intake, lower levels of physical activity, a higher BMI, and a higher consumption of carbonated beverages than controls. The prevalence of risk factors was not, however, significantly higher than controls in children with a single fracture.

CONCLUSIONS

Children with fractures have a lower bone mass for body size than children without fractures. Modifiable risk factors such as diet and exercise increase the risk of recurrent fractures.

A genetic approach to fracture epidemiology in childhood

The purpose of this report is to provide a review of both childhood fracture epidemiology and known heritable causes for fracture predisposition to the Medical Geneticist, who is frequently consulted to assess children with multiple or unexplained fractures for a physiologic etiology. A detailed knowledge of the clinical and laboratory evaluation for osteogenesis imperfecta (OI) and other single-gene disorders is obviously essential to complete a useful evaluation of such children. The experienced clinician will immediately recognize that single gene disorders represent only a small fraction of these patients. In infants, non-accidental trauma (NAT) unfortunately is the likely explanation for the fracture pattern, but in some infants, and certainly in older children with recurrent fractures, no medical explanations can be found. Recent studies in which bone mineral density (BMD) has been associated with genetic variation at a number of candidate genes are promising but these studies are too premature yet to be used clinically. Nonetheless, we do expect that in the future whole-genome approaches in conjunction with key clinical and epidemiological variables may be combined through an informatics approach to create better predictors of fracture susceptibility for these populations of patients.

Bone abnormalities in adolescent leptin-deficient mice

Ob/ob and db/db mice have different aberrations in leptin signaling that both lead to abnormalities in bone mineral density (BMD), and bone histological and histomorphometric outcomes. A few studies have directly compared bone metabolism in ob/ob and db/db mice, and biomechanical strength properties that are surrogate measures of fracture risk, have not been extensively studied. This study compared bone mineral content (BMC), BMD and biomechanical strength properties of femurs and lumbar vertebrae among 10 week old male ob/ob, db/db and C57Bl/6 wildtype (WT) mice. Femurs and lumbar vertebrae were specifically studied to determine if trabecular and cortical bone are regulated by leptin in a similar manner in ob/ob and db/db mice. Femurs of ob/ob and db/db mice had lower BMC, BMD and biomechanical strength properties, including peak load, compared to WT mice. In contrast, lumbar vertebrae BMC and BMD did not differ among genotypes, nor did the peak load from compression testing of an individual lumbar vertebra differ among groups. These findings suggest that leptin deficiency in adolescent male mice first results in changes in femurs, a representative long bone, and alterations in lumbar vertebrae may occur later in life.

The impact of childhood obesity on musculoskeletal form

Despite the greater prevalence of musculoskeletal disorders in obese adults, the consequences of childhood obesity on the development and function of the musculoskeletal system have received comparatively little attention within the literature. Of the limited number of studies performed to date, the majority have focused on the impact of childhood obesity on skeletal structure and alignment, and to a lesser extent its influence on clinical tests of motor performance including muscular strength, balance and locomotion. Although collectively these studies imply that the functional and structural limitations imposed by obesity may result in aberrant lower limb mechanics and the potential for musculoskeletal injury, empirical verification is currently lacking. The delineation of the effects of childhood obesity on musculoskeletal structure in terms of mass, adiposity, anthropometry, metabolic effects and physical inactivity, or their combination, has not been established. More specifically, there is a lack of research regarding the effect of childhood obesity on the properties of connective tissue structures, such as tendons and ligaments. Given the global increase in childhood obesity, there is a need to ascertain the consequences of persistent obesity on musculoskeletal structure and function. A better understanding of the implications of childhood obesity on the development and function of the musculoskeletal system would assist in the provision of more meaningful support in the prevention, treatment and management of the musculoskeletal consequences of the condition.

Sex difference in the effect of puberty on the relationship between fat mass and bone mass in 926 healthy subjects, 6 to 18 years old

OBJECTIVE

Understanding factors influencing bone mineral accrual is critical to optimize peak bone mass during childhood. The epidemic of pediatric obesity and reported higher incident of fracture risk in obese children led us to study the influence of fat mass on bone mineral content (BMC) in children.

RESEARCH METHODS AND PROCEDURES

Height; weight; pubertal stage; and BMC, non-bone fat-free mass (nbFFM), and fat mass (FM) by DXA were obtained in a multiethnic group of healthy children (444 girls/482 boys; 6 to 18 years old) recruited in the New York metropolitan area. Regression techniques were used to explore the relationship between BMC and FM, with age, height, nbFFM, pubertal stage, sex, and ethnicity as covariates.

RESULTS

Because there were significant sex interactions, separate regression analyses were performed for girls and boys. Although ln(nbFFM) was the greatest predictor of ln(BMC), ln(FM) was also a significant predictor in prepubertal boys and all girls but not in pubertal boys. This effect was independent of ethnicity.

DISCUSSION

FM was a determinant of BMC in all girls but in only prepubertal boys. Our study confirms nbFFM as the greatest predictor of BMC but is the first to find a sex difference in the effect of puberty on the relationship of FM to BMC. Our results suggest that, in two individuals of the same sex and weight, the one with greater fat mass will have lower BMC, especially pubertal boys. The implications of these findings for achievement of optimal peak bone mass in a pediatric population with an unprecedented incidence of overweight and "overfat" status remain to be seen.

Childhood onset arthritis is associated with an increased risk of fracture: a population based study using the General Practice Research Database

BACKGROUND

Childhood onset arthritis is associated with low bone mass and strength.

OBJECTIVE

To determine whether childhood onset arthritis is associated with greater fracture risk.

METHODS

In a retrospective cohort study all subjects with onset of arthritis between 1 and 19 years of age in the United Kingdom General Practice Research Database were identified. As controls, all sex and age matched subjects from a practice that included a subject with arthritis were included. Incidence rate ratios (IRRs) for first fracture were generated using Mantel-Haenszel methods and Poisson regression.

RESULTS

1939 subjects with arthritis (51% female) and 207 072 controls (53% female) were identified. The median age at arthritis diagnosis was 10.9 years. A total of 129 (6.7%) first fractures were noted in subjects with arthritis compared with 6910 (3.3%) in controls over a median follow up of 3.90 and 3.95 years in the subjects with arthritis and controls, respectively. The IRR (95% confidence interval) for first fracture among subjects with arthritis, compared with controls, according to the age at the start of follow up were 1.49 (0.91 to 2.31) for age <10 years, 3.13 (2.21 to 4.33) at 10-15 years, 1.75 (1.18 to 2.51) at 15-20 years, 1.40 (0.91 to 2.08) at 20-45 years, and 3.97 (2.23 to 6.59) at >45 years.

CONCLUSIONS

Childhood onset arthritis is associated with a clinically significant increased risk of fracture in children, adolescents and, possibly, adults. Studies are urgently needed to characterise the determinants of structural bone abnormalities in childhood arthritis and devise prevention and treatment strategies.

Calcium supplementation for improving bone mineral density in children

BACKGROUND

Clinical trials have shown that calcium supplementation in children can increase bone mineral density (BMD) although this effect may not be maintained. There has been no quantitative systematic review of this intervention.

OBJECTIVES

. To determine the effectiveness of calcium supplementation for improving BMD in children. . To determine if any effect varies by sex, pubertal stage, ethnicity or level of physical activity, and if any effect persists after supplementation is ceased.

SEARCH STRATEGY

We searched CENTRAL, (Cochrane Central Register of Controlled Trials) (Issue 3, 2005), MEDLINE (1966 to 1 April 2005), EMBASE (1980 to 1 April 2005), CINAHL (1982 to 1 April 2005), AMED (1985 to 1 April 2005), MANTIS (1880 to 1 April 2005) ISI Web of Science (1945 to 1 April 2005), Food Science and Technology Abstracts (1969 to 1 April 2005) and Human Nutrition (1982 to 1 April 2005). Conference abstract books (Osteoporosis International, Journal of Bone and Mineral Research) were hand-searched.

SELECTION CRITERIA

Randomised controlled trials of calcium supplementation (including by food sources) compared with placebo, with a treatment period of at least 3 months in children without co-existent medical conditions affecting bone metabolism. Outcomes had to include areal or volumetric BMD, bone mineral content (BMC), or in the case of studies using quantitative ultrasound, broadband ultrasound attenuation and ultrasonic speed of sound, measured after at least 6 months of follow-up.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data including adverse events. We contacted study authors for additional information.

MAIN RESULTS

The 19 trials included 2859 participants, of which 1367 were randomised to supplementation and 1426 to placebo. There was no heterogeneity in the results of the main effects analyses to suggest that the studies were not comparable. There was no effect of calcium supplementation on femoral neck or lumbar spine BMD. There was a small effect on total body BMC (standardised mean difference (SMD) +0.14, 95% CI+0.01, +0.27) and upper limb BMD (SMD +0.14, 95%CI +0.04, +0.24). Only the effect in the upper limb persisted after supplementation ceased (SMD+0.14, 95%CI+0.01, +0.28). This effect is approximately equivalent to a 1.7% greater increase in supplemented groups, which at best would reduce absolute fracture risk in children by 0.1-0.2%per annum. There was no evidence of effect modification by baseline calcium intake, sex, ethnicity, physical activity or pubertal stage. Adverse events were reported infrequently and were minor.

AUTHORS' CONCLUSIONS

While there is a small effect of calcium supplementation in the upper limb, the increase in BMD which results is unlikely to result in a clinically significant decrease in fracture risk. The results do not support the use of calcium supplementation in healthy children as a public health intervention. These results cannot be extrapolated to children with medical conditions affecting bone metabolism.

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.

Is significant cystic fibrosis-related liver disease a risk factor in the development of bone mineralization abnormalities?

In order to assess the effects of significant cystic fibrosis-related liver disease (CFLD) on bone health, we compared the bone mineral status of older children and adolescents with CFLD to those with cystic fibrosis (CF) alone. Thirteen children (age range, 10-19 years) from our clinical CF services were identified with significant CFLD (9 of these 13 patients had clinical and radiological evidence of portal hypertension). This cohort was then matched by age, gender, and anthropometric measurements with equal numbers of patients with CF alone. All patients had a dual-energy X-ray absorptiometry (DEXA) scan to determine bone mineral content (BMC), bone area (BA), bone mineral density (BMD), and bone mineral apparent density (BMAD) in the region of the lumbar spine. Blood was drawn to determine serum vitamin A, D, E, and K status and liver function tests. The best forced expired volume in 1 sec (FEV1) for each patient in the 12 months around the time of the scan was also documented. Patients with CFLD had slightly worse FEV1 (82 +/- 20% vs. 91 +/- 16%, P = 0.05) and significantly higher alanine aminotransferase (65.5 +/- 35 IU/l vs. 30 +/- 20 IU/l, P = 0.01) than those with CF alone. The mean lumbar spine BA, BMC, BMD, and BMAD were not different between children with CFLD and CF. In conclusion, the presence of significant liver disease in children with CF does not appear to be an additional risk factor for the development of abnormal bone mineralization.

Childhood fractures are associated with decreased bone mass gain during puberty: an early marker of persistent bone fragility?

Whether peak bone mass is low among children with fractures remains uncertain. In a cohort of 125 girls followed over 8.5 years, 42 subjects reported 58 fractures. Among those, BMC gain at multiple sites and vertebral bone size at pubertal maturity were significantly decreased. Hence, childhood fractures may be markers of low peak bone mass acquisition and persistent skeletal fragility.

INTRODUCTION

Fractures in childhood may result from a deficit in bone mass accrual during rapid longitudinal growth. Whether low bone mass persists beyond this period however remains unknown.

MATERIALS AND METHODS

BMC at the spine, radius, hip, and femur diaphysis was prospectively measured over 8.5 years in 125 girls using DXA. Differences in bone mass and size between girls with and without fractures were analyzed using nonparametric tests. The contribution of genetic factors was evaluated by mother-daughter correlations and that of calcium intake by Cox proportional hazard models.

RESULTS

Fifty-eight fractures occurred in 42 among 125 girls (cumulative incidence, 46.4%), one-half of all fractures affecting the forearm and wrist. Girls with and without fractures had similar age, height, weight. and calcium intake at all time-points. Before and during early puberty, BMC and width of the radius diaphysis was lower in the fracture compared with no-fracture group (p < 0.05), whereas aBMD and BMAD were similar in the two groups. At pubertal maturity (Tanner's stage 5, mean age +/- SD, 16.4 +/- 0.5 years), BMC at the ultradistal radius (UD Rad.), femur trochanter, and lumbar spine (LS), and LS projected bone area were all significantly lower in girls with fractures. Throughout puberty, BMC gain at these sites was also decreased in the fracture group (LS, -8.0%, p = 0.015; UD Rad., -12.0%, p = 0.004; trochanter, -8.4%, p = 0.05 versus no fractures). BMC was highly correlated between prepuberty and pubertal maturity (R = 0.54-0.81) and between mature daughters and their mothers (R = 0.32-0.46). Calcium intake was not related to fracture risk.

CONCLUSIONS

Girls with fractures have decreased bone mass gain in the axial and appendicular skeleton and reduced vertebral bone size when reaching pubertal maturity. Taken together with the evidence of tracking and heritability for BMC, these observations indicate that childhood fractures may be markers for low peak bone mass and persistent bone fragility.

Evaluation of bone density in children with slipped capital femoral epiphysis

Slipped capital femoral epiphysis (SCFE) is a condition seen during the preadolescent growth spurt, often in obese children and in children with endocrine disorders. Given that endocrine factors also play a role in bone density, a link between low bone mineral density (BMD) and SCFE was proposed. Dual energy X-ray absorptiometry (DXA) scanning of the spine and hips was performed on 12 children with SCFE and on 5 overweight children without this hip disorder. All scans were performed by the same technician using a Hologic Delphi W densitometer and were interpreted by a pediatric orthopedic surgeon certified in clinical densitometry. Z-scores were obtained using a pediatric database. Mean and standard deviation of the Z-scores were calculated, and paired t tests were used to assess differences between these subjects and the expected norm. The SCFE patients' Z-scores at each of the skeletal sites assessed (spine, femoral neck, and total hip) were greater than the mean by an average of 1 standard deviation. The control subjects' BMD was also greater than the mean. The P values were less then 0.05. These results suggest that children with SCFE do not have low BMD, but show bone density significantly greater then expected for age and sex. Although BMD is endocrinologically driven and endocrinologic abnormalities are implicated in SCFE, there appears to be no correlation between low BMD and SCFE.

Determinants of bone mass and bone size in a large cohort of physically active young adult men

The determinants of bone mineral density (BMD) at multiple sites were examined in a fit college population. Subjects were 755 males (mean age = 18.7 years) entering the United States Military Academy. A questionnaire assessed exercise frequency and milk, caffeine, and alcohol consumption and tobacco use. Academy staff measured height, weight, and fitness. Calcaneal BMD was measured by peripheral dual-energy x-ray absorptiometry (pDXA). Peripheral-quantitative computed tomography (pQCT) was used to measure tibial mineral content, circumference and cortical thickness. Spine and hip BMD were measured by DXA in a subset (n = 159). Mean BMD at all sites was approximately one standard deviation above young normal (p < 0.05). African Americans had significantly higher hip, spine and heel BMD and greater tibial mineral content and cortical thickness than Caucasians and Asians. In Caucasians (n = 653), weight was a significant determinant of BMD at every skeletal site. Prior exercise levels and milk intake positively related to bone density and size, while caffeine had a negative impact. There was an apparent interaction between milk and exercise in BMD at the heel, spine, hip and tibial mineral content and cortical thickness. Our data confirm the importance of race, body size, milk intake and duration of weekly exercise as determinants of BMD and bone size.

Association between bone density and fractures in children: a systematic review and meta-analysis

OBJECTIVE

The objective of this article was to systematically review all published studies that investigated the association between bone density and fractures in children.

DESIGN

Potentially relevant articles were identified by searching electronic databases. Duplicates were removed, abstracts were inspected, and relevant articles were obtained. Studies were included in the systematic review if participants were <16.0 years old, were healthy, had extractable data on bone mass, and had fractures as the outcome.

RESULTS

Ten case-control studies were identified. No prospective studies were found. There was no evidence of heterogeneity between studies or of funnel-plot asymmetry. Eight of the studies were included in the meta-analysis, because they presented results as means and standard deviations of bone density in cases and controls. The pooled standardized mean difference for bone mass in children with and without fractures, from a fixed-effects model, was -0.32 (95% confidence interval: -0.43 to -0.21).

CONCLUSIONS

Evidence for an association between bone density and fractures in children is limited. The results from this meta-analysis suggest that there is an association between low bone density and fractures in children. Although there was no evidence of heterogeneity or publication bias, this meta-analysis is based on case-control studies that are prone to bias. Large, well-conducted prospective cohort studies are required to confirm the association between bone density and fractures in children.

Children who experience their first fracture at a young age have high rates of fracture

Rate of fracture was examined according to age at first fracture in 313 New Zealand children (145 girls, 168 boys) under l3 years of age (95.4% of a consecutive series of children treated at one hospital for a recent confirmed fracture at any site). In their lifetimes they had experienced 468 separate fracture events, over half (54.7%) occurring in the 32.3% of children breaking bones on more than one occasion. Children experiencing a first fracture before 4 years of age had 36.7 (95%CI 30.7-44.1) fractures per l00 years of exposure: this was a significantly higher rate than that of children experiencing their first fracture later in life. Thus, using the <4.0 year age group as a reference, we found that rate ratios (adjusted for gender) for groups that had suffered the first fracture at later ages were: first fracture between 4.0 and 6.99 years, 0.77 (95%CI 0.58-1.03); first fracture between 7.0 and 9.99 years, 0.63 (95%CI 0.42-0.94); first fracture between 10.0 and 12.99 years, 0.48 (95% CI 0.32-0.72). Asthma was over-represented (31% seen, 25% expected), and a high proportion of the sample (32.9%) used corticosteroid medications; however, neither characteristic affected age at first fracture. In contrast, the large number (n= 42) of youngsters (13.4% of the sample) reporting adverse reactions to milk were younger at first fracture than children without reactions to milk (P<0.05). We conclude that children experiencing their first fracture at a young age have high rates of fracture and should be targeted for advice to improve their bone strength.

Optimizing bone health and calcium intakes of infants, children, and adolescents

Most older children and adolescents in the United States currently do not achieve the recommended intake of calcium. Maintaining adequate calcium intake during childhood and adolescence is necessary for the development of peak bone mass, which may be important in reducing the risk of fractures and osteoporosis later in life. Optimal calcium intake is especially relevant during adolescence, when most bone mineral accretion occurs. Because of the influence of the family's diet on the diet of children and adolescents, adequate calcium intake by all members of the family is important. Assessment of calcium intake can be performed in the physician's office. A well-rounded diet including low-fat dairy products, fruits, and vegetables and appropriate physical activity are important for achieving good bone health. Establishing these practices in childhood is important so that they will be followed throughout the life span.

A mother-based intervention trial for osteoporosis prevention in children

OBJECTIVE

To assess whether a lifestyle intervention delivered to mothers might impact on osteoporosis preventive behaviors in their children.

METHODS

We performed a 2-year randomized controlled trial of individualized bone mineral density feedback with either an osteoporosis information leaflet, or small group education, in a population-based sample of 354 mothers from Southern Tasmania, Australia in 2000-02. Main outcomes were maternal report of calcium intake and physical activity change in their children.

RESULTS

Receiving small group education was associated with mothers' report of increasing children's calcium intake (odds ratio 2.3, 95% confidence interval 1.4, 3.8), as was low t-score feedback (odds ratio 2.0, 95% confidence interval 1.2, 3.3). Mothers who increased their own physical activity were more often reported increasing both physical activity (odds ratio 2.7, 95% confidence interval 1.5, 5.0) and calcium intake in their children (odds ratio 2.2, 95% confidence interval 1.3, 3.7). Mothers who commenced calcium supplements more often reported increasing children's calcium intake (odds ratio 2.6, 95% confidence interval 1.0, 6.7) but not physical activity.

CONCLUSIONS

Both bone mineral density feedback and small group education delivered to mothers are effective at inducing maternally reported osteoporosis preventive behavior change in their children. These results require confirmation by studies with objective outcome measures.

Adaptation of the Carter method to adjust lumbar spine bone mineral content for age and body size: application to children who were born preterm

In adults, the Carter method allows the separation of the lumbar spine bone mineral content (BMC) into its constituents; bone volume (BV) and volumetric density (bone mineral apparent density [BMAD]). However, this method is not widely used in pediatric studies and does not account for the effects of body habitus on bone mass. The aims of this study were to modify the Carter method for use in children by developing an approach that adjusts separately for age and body height, and to test whether lumbar spine bone mass is normal in children born who were born preterm. Twenty-five preterm-born children were matched to a term-born child. Lumbar spine bone mass was measured using dual-energy X-ray absorptiometry. The BV and BMAD were calculated. Z-scores based on age and height were calculated. The preterm group had reduced absolute height, weight, BMC, BV, and BMAD, and reduced height, weight, and BMC for their age. The BMC was appropriate for height. The BV was appropriate for age. The BMAD was reduced for age but appropriate for height. In preterm children, the major abnormality at the lumbar spine is a decrease in volumetric density; however, this decrease is proportional with their reduced stature, and we speculate that there is no reduction in the strength of the lumbar spine.

Relation of body composition, fat mass, and serum lipids to osteoporotic fractures and bone mineral density in Chinese men and women

BACKGROUND

Higher fat mass may be an independent risk factor for osteoporosis and osteoporotic fractures.

OBJECTIVE

We aimed to determine the independent contribution of fat mass to osteoporosis and to estimate the risk of osteoporotic fractures in relation to body weight, lean mass, and other confounders.

DESIGN

This was a community-based, cross-sectional study of 7137 men, 4585 premenopausal women, and 2248 postmenopausal women aged 25-64 y. Total-body and hip bone mineral content (BMC) and bone mineral density (BMD) and body composition were measured by dual-energy X-ray absorptiometry. Serum lipids were measured. Sex- and menopause-specific multiple generalized linear models were applied.

RESULTS

Across 5-kg strata of body weight, fat mass was significantly inversely associated with BMC in the whole body and total hip. When we compared the highest quartile with the lowest quartile of percentage fat mass in men, premenopausal women, and postmenopausal women, the adjusted odds ratios (95% CIs) of osteoporosis defined by hip BMD were 5.2 (2.1, 13.2), 5.0 (1.7, 15.1), and 6.9 (4.3, 11.2), respectively. Significant linear trends existed for higher risks of osteoporosis, osteopenia, and nonspine fractures with higher percentage fat mass. Significant negative relations were found between whole-body BMC and cholesterol, triacylglycerol, LDL, and the ratio of HDL to LDL in all groups.

CONCLUSIONS

Risks of osteoporosis, osteopenia, and nonspine fractures were significantly higher for subjects with higher percentage body fat independent of body weight, physical activity, and age. Thus, fat mass has a negative effect on bone mass in contrast with the positive effect of weight-bearing itself.

Newer Perspectives on Calcium Nutrition and Bone Quality

It is now generally accepted that an adequate calcium intake is important for building and maintaining a skeleton that expresses quantitatively the full genetic program and reduces lifetime fracture risk. In this brief review we focus mainly on a new and growing body of evidence indicating a benefit of adequate calcium intake on qualitative features of the skeleton that, independent of the quantity of bone, themselves influence skeletal strength and fragility. Change in bone mass and size during growth are dependent on both calcium intake and exercise, with the largest differences being observed in prepubertal children who have both high exercise levels and high calcium intakes. Much of this benefit is expressed as increased bone diameter (and hence stiffness). Fracture risk peaks at about the time of puberty and is inversely related to bone mass. However, even prepubertally, children with low calcium intakes have been reported to have a fracture rate 2.7x that of their birth cohort. Bone remodeling triples from age 50 to 65 in typical women and is now recognized to have primarily a homeostatic basis. While remodeling improves bone strength by repairing acquired defects, homeostatic remodeling, while necessary to maintain blood calcium levels, contributes only structural weakness to bone. High calcium intakes in postmenopausal and older women reduce this homeostatic remodeling to approximately pre-menopausal values and improve bone strength immediately, well prior to any appreciable change in bone mass.

Nutrient Inadequacy in Obese and Non-Obese Youth

Purpose: In this study, the Dietary Reference Intake standards were used to evaluate the prevalence of inadequate intakes of micronutrients in obese and non-obese youth.

Methods: Dietary intake was analyzed with a dietary history taken by a registered dietitian. The obese group (n=156) had a body mass index (BMI) above the 95th percentile for age and sex. The non-obese group (n=90) was between the tenth and 85th BMI percentiles.

Results: In the obese subjects, the prevalence of inadequate intakes was 81% for vitamin E and 27% for magnesium; the proportions with intakes below the Adequate Intakes (AIs) for calcium and vitamin D were 55% and 46%, respectively. The obese children consumed 124% of estimated need for energy, 32% of which came from fat. The non-obese had a similar prevalence of inadequate intakes (vitamin E, 93%; magnesium, 29%; calcium, 51%; vitamin D, 44%). They consumed 107% of estimated need for energy, and 31% of energy came from fat. For both groups, all other nutrient intakes were adequate.

Conclusions: Even though children may consume an excess of energy, they may not be meeting all of their micronutrient needs.

Comparison of phalangeal ultrasound and dual energy X-ray absorptiometry in healthy male and female adolescents

The aims of this study were to determine if there is a correlation between dual energy X-ray absorptiometry (DXA) and phalangeal quantitative ultrasound (QUS) in identifying children and adolescents with low bone density, and to assess if body size influences the results of the two techniques to the same degree. Measurements were performed in 67 girls and 83 boys aged 14 to 19 y using DBM Sonic 1200 (IGEA, Carpi, Italy) and the DXA equipment (LUNAR Radiation Corp., Madison, WI, USA). Twelve adolescents (eight males and four females) reported a past history of nonosteoporotic fractures. Lumbar spine bone mineral density (LS BMD), total body bone mineral density (TB BMD) and total body bone mineral content (TB BMC) correlated positively with age, height, BMI and weight, in both genders. Amplitude-dependent speed of sound (Ad-SOS) was positively correlated with age, height and Tanner stages in both genders and negatively correlated with BMI in females. TB BMD, TB BMC and LS BMD positively correlated with Ad-SOS only in males. In females, there were no significant correlations between Ad-SOS, TB BMD, TB BMC and LS BMD measurements. Twelve teenagers with previous fractures (high impact fractures) were found to have lower DXA and QUS values than age-matched teenagers without fractures but the statistical significance was found only in relation to TB BMD values (p = 0.02). In conclusion, we obtained results similar to those that have been reported by other authors using different QUS techniques. Furthermore, the Ad-SOS measurements taken at the distal metaphysis of the proximal phalanges correlate poorly with LS BMD and TB BMD measured by DXA in growing subjects.

Bone and body composition of children and adolescents with repeated forearm fractures

DXA measurements in 90 children and adolescents with repeated forearm fractures showed reduced ultradistal radius BMC and BMD values and elevated adiposity, suggesting site-specific bone weakness and high body weight increase fracture risk. Symptoms to cow milk, low calcium intakes, early age of first fracture, and overweight were over-represented in the sample.

INTRODUCTION

Although many apparently healthy children fracture their forearms repeatedly during growth, no previous studies of their bone health and body composition have been undertaken. Nor has the prevalence of established risk factors for fracture in such a population been assessed.

MATERIALS AND METHODS

Ninety children and adolescents (47 girls and 43 boys) 5-19 years of age, who had experienced at least two fractures of the forearm, were studied. Bone size and mineralization were assessed using DXA at the ultradistal radius, one-third radius, neck of femur, hip trochanter, lumbar spine, and total body. Total body lean mass and fat mass were also determined. The prevalence of six risk factors for fracture were also examined, and their influence on ultradistal BMC Z scores was assessed.

RESULTS

Participants experienced 295 fractures (74.9% forearm). Children with an early age of first fracture had higher rates of fracture per l00 years of exposure than those fracturing later. Four risk factors for fracture were over-represented in observed versus expected percentages: early age of first fracture (27.7% versus 11.3%), adverse symptoms to cow milk (22.2% versus 6.7%), low dietary calcium intake (20% versus 4.5%), and overweight (33.3% versus 15.5%). However, physical activity levels were similar to the reference population. Z scores for BMC and BMD were reduced, particularly at the ultradistal radius, whereas Z scores for weight, body mass index, fat mass, and body fat percentage were increased. Mean (SD) BMC Z scores were lowest at the ultradistal radius, -0.66 (1.22), where symptoms to milk were associated with reduced values (p < 0.009) and overweight with increased values (p < 0.003).

CONCLUSIONS

Our results suggest site-specific weakness and high body weight contribute to fracture risk in children and adolescents who fracture their forearms repeatedly. These findings are consonant with work showing adult Colles fractures increase as ultradistal radius BMD falls and with evidence that overweight children and adolescents are fracture prone.

The characteristics of fractures in Polish adolescents aged 16-20 years

The aim of the study was to identify associations between fractures in childhood and family, anthropometric and lifestyle factors. Among 1,246 subjects aged 16.3-20.6 years (539 boys, 707 girls), based on a questionnaire, 869 were fracture-free while 377 (30.26%) had fractures. Of those reporting fractures, 146 reported multiple fractures (12% of studied population, 39% of all fractures). More boys had fractures than girls (35.6% vs 24.9%, p < 0.001). Fracture sites included: forearm (37%), fingers (23%) wrist (16%), ankle (14%), humerus (10%), tibia (8%) clavicle (7%) and femoral shaft / neck (3%). Among adolescents with multiple fractures, 52% also reported fractures in at least one family member, compared with 29% of those without a fracture history. Fractures in siblings and mothers (but not fathers) accounted for 44% of the liability in adolescents' fractures. Subjects with multiple fractures reported more time at the computer than those without fractures and reported more time participating in team sports, and 18.6% avoided milk, whereas 12.4% of those without fractures reported milk-free diets. Using a logistic regression model, none of the lifestyle factors, except for computer use, were independently associated with fractures. Fractures, particularly multiple fractures, are common in childhood and adolescence. Familial clustering of fractures suggests shared genetic and environmental factors are responsible.

Two-year changes in bone and body composition in young children with a history of prolonged milk avoidance

No previous longitudinal studies of calcium intake, anthropometry and bone health in young children with a history of avoiding cow's milk have been undertaken. We report the 2-year changes of a group of 46 Caucasian children (28 girls, l8 boys) aged 8.1+/-2.0 years (mean +/- SD) who had low calcium intakes at baseline and were short in stature, with elevated body mass index, poor skeletons and lower Z scores for both areal bone mineral density (BMD, in grams per square centimeter) and volumetric density (bone mineral apparent density, BMAD, in grams per cubic centimeter), compared with a reference population of milk drinkers. At follow-up, adverse symptoms to milk had diminished and modest increases in milk consumption and calcium intake had occurred. Total body bone mineral content (BMC) and bone area assessed by dual energy X-ray absorptiometry had increased (P<0.05), and calcium intake from all sources was associated with both these measures (P<0.05). However, although some catch-up in height had taken place, the group remained significantly shorter than the reference population (Z scores -0.39+/-1.14), with elevated body mass index (Z scores 0.46+/-1.0). The ultradistal radius BMC Z scores remained low (-0.31+/-0.98). The Z scores for BMD had improved to lie within the normal range at predominantly cortical sites (33% radius, neck of femur and hip trochanter) but had worsened at predominantly trabecular sites (ultradistal radius and lumbar spine), where values lay below those of the reference group (P<0.05). Similarly, although volumetric BMAD Z scores at the 33% radius had normalized, BMAD Z scores at the lumbar spine remained below the reference population at follow-up (-0.67+/-1.12, P<0.001). Our results demonstrate persisting height reduction, overweight and osteopenia at the ultradistal radius and lumbar spine in young milk avoiders over 2 years of follow-up.

Pubertal development and its influences on bone mineral density in Australian children and adolescents with cystic fibrosis

BACKGROUND

Pubertal delay is thought to contribute to suboptimal peak bone mass acquisition in young people with cystic fibrosis (CF), leading to an increased fracture incidence. This study aims to compare pubertal development in young people with CF with that of a local healthy population and assess the influence it has on areal bone mineral density (aBMD).

METHODS

Tanner stage, age of menarche, bone age (BA), sex hormone levels and aBMD were examined in 85 individuals with CF (aged 5.3-18.1 years, 39 females) and 100 local controls (5.6-17.9 years, 54 females).

RESULTS

Tanner stage and age of menarche were not significantly different between controls and CF. Tanner stage-adjusted mean values for follicle stimulating hormone (FSH), luteinizing hormone (LH) and testosterone (T) were lower in males with CF (FSH: P = 0.004, LH: P = 0.01 and T: P = 0.002). Bone age was delayed in adolescents with CF compared to controls (chronological age-BA: controls = 0.13 years (SE = 0.16), CF = 0.95 years (SE = 0.22), P = 0.003). Areal bone mineral density (adjusted for age, sex, height and lean tissue mass) was not significantly different between CF and controls. Moderate negative correlations were found between delayed BA and weight (r = -0.41, P < 0.001) and height (r = -0.41, P < 0.001).

CONCLUSIONS

There was no evidence of clinical pubertal delay or low aBMD (adjusted for short stature and lean tissue mass) in young people with CF when compared with a local population, despite lower nutritional markers, height and weight and delayed skeletal maturation.

Do young New Zealand Pacific Island and European children differ in bone size or bone mineral?

Although Pacific Island adults have been shown to have larger bones and greater bone mineral density than caucasians, no previous studies have been undertaken to determine whether differences are present in prepubertal children. Forty-one Pacific Island children (both parents of Pacific Island descent) and 38 European children, aged 3 to 7 years, living in New Zealand were studied. Heights and weights were determined by simple anthropometry and body mass index (BMI, kg/m2) was calculated. Body composition, bone size, and bone mineral content (BMC, g) were measured by dual energy X-ray absorptiometry (DXA) of the total body and the non-dominant forearm. Compared to European children, in data adjusted for age and gender, Pacific Island children had significantly greater (P < 0.05) BMC in the total body (12%), the ultradistal radius (16%), and the 33% radius (8%), and also greater total body bone area (10%). Bone mineral density (BMD, g/cm2) was higher only at the ultradistal radius (11%). However, after adjustment for body weight, in particular lean mass, no differences were seen between Pacific Island and European children in any bone measure. The larger bone area and BMC of young Pacific Island children can be explained by their greater height and weight. Therefore, this study has shown that prepubertal Pacific Island children do not have greater bone size or BMC for their weight.

Bone mass acquisition in healthy children

Although 80% of the variance in bone mass is determined genetically, there are many other factors which influence the accumulation of bone in early life and affect future risks of osteoporosis. This review considers the genetic, fetal, and environmental influences on bone mass acquisition in healthy children, and highlights important areas where paediatricians may have a role by counselling children and their families to adopt a healthy lifestyle which promotes bone health.

Composition of the fat-free mass in obese and nonobese children: matched case-control analyses

OBJECTIVE

Most body composition techniques assume constant properties of the fat-free mass (FFM), such as hydration, density and mineralisation. Previous studies suggested that FFM composition may change in childhood obesity; however, this issue has not been investigated in detail.

AIM

To compare FFM composition in obese and nonobese children.

DESIGN

Observational matched case-control analyses.

SUBJECTS

A total of 28 obese children (13 boys, 15 girls) and 22 nonobese children (10 boys, 12 girls) aged 7-14 y. Obesity was defined as body mass index centile >95.

METHODS

Measurements were made of weight, height, total body water, and body volume. Bone mineral content was estimated in a subsample. Body composition was calculated using three- and four-component models.

RESULTS

According to the three-component model (n=22 matched pairs), obese children had greater hydration (P<0.05), and reduced density (P=0.057) of FFM. According to the four component model (n=11 pairs), obese children had greater hydration (P<0.01) and reduced density (P<0.002) of FFM. The mineralisation of FFM was increased, but not significantly so.

CONCLUSION

The greater hydration and reduced density of FFM of obese children should be taken into account if body composition is to be measured with optimum accuracy during treatment programmes. These differences may be addressed by using multicomponent rather than two-component models of body composition. Although the greater mineralisation of FFM in obese children was not significant in the present study, the four-component model is best able to address the combined differences in hydration and mineralisation that occur in childhood obesity.

Assessment of bone mass following renal transplantation in children

Throughout childhood and adolescence, skeletal growth results in site-specific increases in trabecular and cortical dimensions and density. Childhood osteoporosis can be defined as a skeletal disorder characterized by compromised bone strength predisposing to an increased risk of fracture. Pediatric renal transplant recipients have multiple risk factors for impaired bone density and bone strength, including pre-existing renal osteodystrophy, delayed growth and development, malnutrition, decreased weight-bearing activity, inflammation, and immunosuppressive therapies. Dual energy X-ray absorptiometry (DXA) is the most-common method for the assessment of skeletal status in children and adults. However, DXA has many important limitations that are unique to the assessment of bone health in children. Furthermore, DXA is limited in its ability to distinguish between the distinct, and sometimes opposing, effects of renal disease on cortical and trabecular bone. This review summarizes these limitations and the difficulties in assessing and interpreting bone measures in pediatric transplantation are highlighted in a review of select studies. Alternative strategies are presented for clinical and research applications.

(n-3) fatty acids reduce the release of prostaglandin E2 from bone but do not affect bone mass in obese (fa/fa) and lean Zucker rats

Childhood obesity is prevalent and linked to the development of Type 2 diabetes mellitus (DM) and poor bone health. Some PUFA enhance bone mass and thus may improve bone health in obese children. The study objective was to determine the effects of dietary (n-6) compared with (n-3) essential PUFA and long-chain PUFA (LCPUFA) on bone in an obese and insulin-resistant state. Male fa/fa (n = 48) and lean Zucker rats (n = 48) were fed diets containing safflower oil [SO, high (n-6) PUFA], flaxseed oil [FXO, high (n-3) PUFA], or menhaden oil [MO, high (n-3) LCPUFA] for 9 wk. Measurements included the following: femur bone area (BA), mineral content (BMC), density (BMD), morphometry and ex vivo release of prostaglandin E(2) (PGE(2)); plasma osteocalcin and C-terminal telopeptides of type I collagen. Differences among groups were detected using 2-way ANOVA. Genotype effects in the fa/fa rats included lower femoral weight, length, BA, and BMC, as well as femoral head and proximal epiphysis widths compared with the lean rats, but BMD was not affected. Femur BA, BMC, and BMD did not differ among the dietary groups, but diaphysis width was elevated in the MO group and PGE(2) release was reduced by the FXO and MO diets. No genotype x diet interactions were observed. These data indicate that the fa/fa Zucker rat is at risk for low bone mass and that dietary (n-3) FA effectively reduce PGE(2) release. Whether reduced PGE(2) will support optimal peak bone mass during childhood and conserve bone mass with aging warrants investigation.

Calcium, dairy products, and bone health in children and young adults: a reevaluation of the evidence

OBJECTIVE

Numerous nutrition policy statements recommend the consumption of 800 to 1500 mg of calcium largely from dairy products for osteoporosis prevention; however, the findings of epidemiologic and prospective studies have raised questions about the efficacy of the use of dairy products for the promotion of bone health. The objective of this study was to review existing literature on the effects of dairy products and total dietary calcium on bone integrity in children and young adults to assess whether evidence supports (1) current recommended calcium intake levels and (2) the suggestion that dairy products are better for promoting bone integrity than other calcium-containing food sources or supplements.

METHODS

A Medline (National Library of Medicine, Bethesda, MD) search was conducted for studies published on the relationship between milk, dairy products, or calcium intake and bone mineralization or fracture risk in children and young adults (1-25 years). This search yielded 58 studies: 22 cross-sectional studies; 13 retrospective studies; 10 longitudinal prospective studies; and 13 randomized, controlled trials.

RESULTS

Eleven of the studies did not control for weight, pubertal status, and exercise and were excluded. Ten studies were randomized, controlled trials of supplemental calcium, 9 of which showed modest positive benefits on bone mineralization in children and adolescents. Of the remaining 37 studies of dairy or unsupplemented dietary calcium intake, 27 studies found no relationship between dairy or dietary calcium intake and measures of bone health. In the remaining 9 reports, the effects on bone health are small and 3 were confounded by vitamin D intake from milk fortified with vitamin D. Therefore, in clinical, longitudinal, retrospective, and cross-sectional studies, neither increased consumption of dairy products, specifically, nor total dietary calcium consumption has shown even a modestly consistent benefit for child or young adult bone health.

CONCLUSION

Scant evidence supports nutrition guidelines focused specifically on increasing milk or other dairy product intake for promoting child and adolescent bone mineralization.

Proximal femur bone geometry is appropriately adapted to lean mass in overweight children and adolescents

It is unclear if the bones of overweight children are appropriately adapted to increased loads. The objective of this study was to compare bone geometry in 40 overweight (body mass index [BMI] > 85th percentile) and 94 healthy weight (BMI < or = 85th percentile) subjects, ages 4-20 years. Dual energy X-ray absorptiometry (Hologic QDR 2000) scans were analyzed at the femoral shaft (FS) and narrow neck (NN) by the Hip Structure Analysis program. Subperiosteal width, cortical thickness and indices of bone axial and bending strength (bone cross-sectional area [CSA] and section modulus [Z]) were measured from bone mass profiles. Multivariate regression models were used to compare overweight and healthy weight subjects. Z was 11 (95% CI 5, 19) and 13 (7, 20) percent higher at the FS and NN, respectively, in overweight subjects (P < 0.001), adjusted for height, maturation and gender. At the NN, higher Z was due to greater subperiosteal width [4% (2, 7)] and bone CSA [10% (5, 16]) and at the FS, to higher bone CSA [10% (5, 16)] and thicker cortices [9% (3, 15)]. When lean mass was added to the models, bone variables did not differ between overweight and healthy weight subjects (P > 0.22), with the exception of NN subperiosteal width [3% (0, 6), P = 0.04]. Fat mass did not contribute significantly to any model. In summary, proximal femur bone geometric strength in overweight children was appropriately adapted to lean mass and height but greater weight in the form of fat mass did not have an independent effect on bone bending strength. These geometric adaptations are consistent with the mechanostat hypothesis that bone strength adapts primarily to muscle forces, not to static loads represented by body weight.

Skeletal age deviation assessed by the Tanner-Whitehouse 2 method is associated with bone mass and fracture risk in children

The aim of this population-based case-control study was to describe the association among skeletal age deviation (SAD), bone density, and upper limb fracture risk in male and female children aged 9-16 years. A total of 321 fracture cases and 321 randomly selected individually matched controls were studied. Skeletal age was assessed by standard atlas. Bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry (DXA) and metacarpal index (MI). There were no significant differences in mean skeletal age or chronological age between fracture cases and controls. However, SAD was associated with total, hand, and female fracture risk (all P<0.05). The fracture associations became nonsignificant after adjustment for BMD and MI in all subgroups with the exception of hand fractures (OR, 0.67/year; 95% CI, 0.47-0.96). SAD was also positively associated with BMD at all sites (r=0.33-0.35, all P<0.05) and MI (r=0.20, P<0.05). The strength of association reduced but remained significant at most sites after adjustment for body size, maturity, age, and sex. In conclusion, SAD is positively associated with measures of bone strength and negatively associated with upper limb fracture risk (especially those of the hand) in children. SAD is simple to measure and gives additional information regarding bone health and fracture risk in children.

Musculoskeletal health in elite male adolescent middle-distance runners

The impact of high training volumes on musculoskeletal adaptations of male adolescents is poorly understood. We compared bone mineral content (BMC) of total body, lumbar spine and proximal femur using Dual X-ray Absorptiometry (Lunar Prodigy, GE Medical Systems, Madison WI) in elite level (n=20), male adolescent middle distance runners (mean 16.8 yrs, range 14-18 yrs) and age-matched (n=20) controls. Athletes averaged 14 hrs of physical activity per week and controls reported participating in physical activity an average of two hrs per week. Total body mass was 10.97 kg less in athletes than controls (p=0.005). Within the total body mass difference, fat tissue mass of athletes was 10.93 kg less in athletes than controls (p= 0.001). Multiple regression analysis identified total body lean mass and total body fat mass as the strongest predictors of total body BMC (R2 0.71). After adjusting for lean tissue mass per kg of body weight (p=0.07), no difference in BMC was detected. Lower limb muscle strength and macronutrient intakes were also measured but no between group differences were found. The number of weeks of training and/or competition missed through injury was not associated with total body BMC (R2=0.19) among athletes. Our results imply high training volumes in middle distance running are not detrimental to musculoskeletal health and are associated with positive body composition profiles in elite adolescent male athletes.

Bone outcomes and technical measurement issues of bone health among children and adolescents: considerations for nutrition and physical activity intervention trials

Weight-bearing physical activity and calcium intake are two important behavioral influences for bone health. Physical-activity and calcium-intake intervention trials with youth have been implemented to evaluate their efficacy and effectiveness to decrease the risk for subsequent osteoporosis and fractures. Technical aspects of bone measurement have not been routinely reported in published trials of youth, even though they can have an impact on study findings and interpretation. This paper provides an overview of the outcome variables reported, and technical issues--such as software and bone detection, growth, and movement--that affect bone mass measurements among children and adolescents. It describes the implications of these issues for the interpretation of intervention effects observed in intervention trials, and provides recommendations for future research.

Stochastic-rheological simulation of free-fall arm impact in children: application to playground injuries

The aim of this study was to develop and pilot a stochastic-rheological biomechanical model to investigate the mechanics of impact fractures in the upper limbs of children who fall in everyday situations, such as when playing on playground equipment. The rheological aspect of the model characterises musculo-skeletal tissues in terms of inertial, elastic and viscous parameters. The stochastic aspect of the model allows natural variation of children's musculo-skeletal mechanical properties to be accounted for in the analysis. The relationship of risk factors, such as fall height, impact surface, child mass and bone density, to the probability of sustaining an injury in playground equipment falls were examined and found to closely match findings in epidemiological, clinical and biomechanical literature. These results suggest that the stochastic-rheological model is a useful tool for the evaluation of arm fracture risk in children. Once fully developed, information from this model will provide the basis for recommendations for modifications to playground equipment and surface standards.

Soft drink and milk consumption, physical activity, bone mass, and upper limb fractures in children: a population-based case-control study

Carbonated beverages have been reported to increase fracture risk in children but the mechanism is unclear. The aim of this population-based case-control study was to investigate the association between soft drink and milk consumption, physical activity, bone mass, and upper limb fractures in children aged 9-16 years. A total of 206 fracture cases and 206 randomly selected individually matched controls were studied. There were 47 hand fractures; 128 wrist and forearm fractures, and 31 upper arm fractures. An interviewer-administered questionnaire was utilized to retrospectively assess last-year physical activity (including television, computer, and video watching) and to recall the average weekly consumption of milk, colas, and total carbonated drinks. Bone mass at the spine, hip, and total body was assessed by dual-energy X-ray absorptiometry (DXA) and metacarpal morphometry. For total fractures, none of the above drink types was significantly different between cases and controls. For wrist and forearm fractures, there was a positive association between cola drink consumption and fracture risk (OR 1.39/unit, 95% CI: 1.01, 1.91). Cola consumption was significantly correlated with television, computer, and video watching (r = 0.20, P = 0.001) but not bone mineral density or milk drinks. After adjustment for television, computer, and video watching and bone mineral density, the association between cola drinks and fracture risk became nonsignificant (OR 1.31/unit, 95% CI: 0.94, 1.83). No association with other fracture sites was observed. In conclusion, cola, but not total carbonated beverage consumption, is associated with increased wrist and forearm fracture risk in children. However, this association is not independent of other factors and appears to be mediated by television watching and bone mineral density but not by decreased milk intake.