More broken bones: a 4-year double cohort study of young girls with and without distal forearm fractures

Metabolic imprinting, programming and epigenetics - a review of present priorities and future opportunities

Metabolic programming and metabolic imprinting describe early life events, which impact upon on later physiological outcomes. Despite the increasing numbers of papers and studies, the distinction between metabolic programming and metabolic imprinting remains confusing. The former can be defined as a dynamic process whose effects are dependent upon a critical window(s) while the latter can be more strictly associated with imprinting at the genomic level. The clinical end points associated with these phenomena can sometimes be mechanistically explicable in terms of gene expression mediated by epigenetics. The predictivity of outcomes depends on determining if there is causality or association in the context of both early dietary exposure and future health parameters. The use of biomarkers is a key aspect of determining the predictability of later outcome, and the strengths of particular types of biomarkers need to be determined. It has become clear that several important health endpoints are impacted upon by metabolic programming/imprinting. These include the link between perinatal nutrition, nutritional epigenetics and programming at an early developmental stage and its link to a range of future health risks such as CVD and diabetes. In some cases, the evidence base remains patchy and associative, while in others, a more direct causality between early nutrition and later health is clear. In addition, it is also essential to acknowledge the communication to consumers, industry, health care providers, policy-making bodies as well as to the scientific community. In this way, both programming and, eventually, reprogramming can become effective tools to improve health through dietary intervention at specific developmental points.

Prevalent fractures are related to cortical bone geometry in young healthy men at age of peak bone mass

Low areal bone mass is a risk factor for fractures in men. Limited data are available on fractures and bone geometry in men, and the relation with sex steroids is incompletely understood. We investigated prevalent fractures in relation to peak bone mass, bone geometry, and sex steroids in healthy young men. Healthy male siblings (n = 677) at the age of peak bone mass (25 to 45 years) were recruited in a cross-sectional population-based study. Trabecular and cortical bone parameters of the radius and cortical bone parameters of the tibia were assessed using peripheral quantitative computed tomography (pQCT). Areal bone mineral density (aBMD) was determined using dual-energy X-ray absorptiometry (DXA). Sex steroids were determined using immunoassays, and fracture prevalence was assessed using questionnaires. Fractures in young men were associated with a longer limb length, shorter trunk, lower trabecular BMD, smaller cortical bone area, and smaller cortical thickness (p < .005) but not with bone-size-adjusted volumetic BMD (vBMD). With decreasing cortical thickness [odds ratio (OR) 1.4/SD, p <or= .001] and decreasing cortical area (OR 1.5/SD, p <or= .001), fracture odds ratios increased. No association between sex steroid concentrations and prevalent fractures was observed. Childhood fractures (<or=15 years) were associated with a thinner bone cortex (-5%, p <or= .005) and smaller periosteal size (-3%, p <or= .005). Fractures occurring later than 15 years of age were associated with a thinner bone cortex (-3%, p <or= .05) and larger endosteal circumference (+3%, p <or= .05) without differences in periosteal bone size. In conclusion, prevalent fractures in healthy young men are associated with unfavorable bone geometry and not with cortical vBMD when adjusting for bone size. Moreover, the data suggest different mechanisms of childhood fractures and fractures during adult life.

Osteoporosis: impact on health and economics

Osteoporosis is a major public health problem through associated fragility fractures. The most common sites of fracture are the hip, spine and wrist, and these have an enormous health and economic impact. All fractures result in some degree of morbidity, but fractures at the hip are associated with the worst outcomes. The worldwide direct and indirect annual costs of hip fracture in 1990 were estimated at US$34.8 billion, and are expected to increase substantially over the next 50 years. Fracture incidence varies between populations, and is set to increase over coming decades as the global population becomes more elderly. This effect will be particularly marked in the developing world, which is additionally assuming more-westernized lifestyles that predispose to increased fracture risk. Strategies to target those at high risk of fracture have been developed, but preventative measures at the public health level are also urgently needed to reduce the burden of this devastating disease.

Relationship of total body fat mass to weight-bearing bone volumetric density, geometry, and strength in young girls

Understanding the influence of total body fat mass (TBFM) on bone during the peri-pubertal years is critical for the development of future interventions aimed at improving bone strength and reducing fracture risk. Thus, we evaluated the relationship of TBFM to volumetric bone mineral density (vBMD), geometry, and strength at metaphyseal and diaphyseal sites of the femur and tibia of young girls. Data from 396 girls aged 8-13 years from the "Jump-In: Building Better Bones" study were analyzed. Bone parameters were assessed using peripheral quantitative computed tomography (pQCT) at the 4% and 20% distal femur and 4% and 66% distal tibia of the non-dominant leg. Bone parameters at the 4% sites included trabecular vBMD, periosteal circumference, and bone strength index (BSI), while at the 20% femur and 66% tibia, parameters included cortical vBMD, periosteal circumference, and strength-strain index (SSI). Multiple linear regression analyses were used to assess associations between bone parameters and TBFM, controlling for muscle cross-sectional area (MCSA). Regression analyses were then repeated with maturity, bone length, physical activity, and ethnicity as additional covariates. Analysis of covariance (ANCOVA) was used to compare bone parameters among tertiles of TBFM. In regression models with TBFM and MCSA, associations between TBFM and bone parameters at all sites were not significant. TBFM explained very little variance in all bone parameters (0.2-2.3%). In contrast, MCSA was strongly related (p<0.001) to all bone parameters, except cortical vBMD. The addition of maturity, bone length, physical activity, and ethnicity did not alter the relationship between TBFM and bone parameters. With bone parameters expressed relative to total body mass, ANCOVA showed that all outcomes were significantly (p<0.001) greater in the lowest compared to the middle and highest tertiles of TBFM. Although TBFM is correlated with femur and tibia vBMD, periosteal circumference, and strength in young girls, this relationship is significantly attenuated after adjustment for MCSA. Nevertheless, girls with higher TBFM relative to body mass have markedly diminished vBMD, geometry, and bone strength at metaphyseal and diaphyseal sites of the femur and tibia.

Pathogenesis of Osteoporosis

As for most multifactorial disorders, the pathogenesis of osteoporosis is complex, and a different set of mechanisms may be operative in any given individual. However, there are certain common causes of bone loss and increased fracture risk with aging in most people. These include genetic factors contributing to the acquisition of peak bone mass, illnesses affecting skeletal growth and development, sex steroid deficiency following the menopause in women and with aging in men, and intrinsic, age-related changes in bone metabolism. Superimposed on these factors are specific secondary causes of bone loss, such as corticosteroid use or other illnesses affecting bone metabolism that may contribute to fracture risk in individuals exposed to these factors. The past decade has witnessed tremendous advances in our understanding of each of these various causes of bone loss, leading to the development of novel, mechanism-based therapeutic approaches to prevent and treat this important public health disorder.

The relationship between fractures and DXA measures of BMD in the distal femur of children and adolescents with cerebral palsy or muscular dystrophy

Children with limited or no ability to ambulate frequently sustain fragility fractures. Joint contractures, scoliosis, hip dysplasia, and metallic implants often prevent reliable measures of bone mineral density (BMD) in the proximal femur and lumbar spine, where BMD is commonly measured. Further, the relevance of lumbar spine BMD to fracture risk in this population is questionable. In an effort to obtain bone density measures that are both technically feasible and clinically relevant, a technique was developed involving dual-energy X-ray absorptiometry (DXA) measures of the distal femur projected in the lateral plane. The purpose of this study is to test the hypothesis that these new measures of BMD correlate with fractures in children with limited or no ability to ambulate. The relationship between distal femur BMD Z-scores and fracture history was assessed in a cross-sectional study of 619 children aged 6 to 18 years with muscular dystrophy or moderate to severe cerebral palsy compiled from eight centers. There was a strong correlation between fracture history and BMD Z-scores in the distal femur; 35% to 42% of those with BMD Z-scores less than -5 had fractured compared with 13% to 15% of those with BMD Z-scores greater than -1. Risk ratios were 1.06 to 1.15 (95% confidence interval 1.04-1.22), meaning a 6% to 15% increased risk of fracture with each 1.0 decrease in BMD Z-score. In clinical practice, DXA measure of BMD in the distal femur is the technique of choice for the assessment of children with impaired mobility.

Fat and bone in children: differential effects of obesity on bone size and mass according to fracture history

Fat mass predicts bone accrual in prepubertal children, but obese children have increased fracture risk. We hypothesised that bone size and mass would vary according to prior fracture in obese children. One hundred and three children (52 obese) underwent dual-energy X-ray absorptiometry (DXA) scanning of the lumbar spine, total body, and radial metaphysis and diaphysis. We derived body size-adjusted bone mineral density (BMD) estimates for each site using commonly employed procedures. Following adjustment for either age, age(2) and weight, or height and weight based on a reference group of nonobese controls without previous fracture, obese children with prior fracture showed a 0.8 to 1.2 SD reduction in total body areal BMD (aBMD), a 3.0 SD decrease in lumbar (L2-4) aBMD, and a 2.0 SD reduction in radial shaft aBMD. These changes were significant at p < .005. Lumbar volumetric BMD (vBMD) calculated by Carter and Kröger algorithms was significantly reduced in obese children with prior fracture (2.0 to 3.3 SD). Eighteen percent of obese children fulfilled the criteria for osteoporosis. Despite greater lean mass for height in obese children (p < .0001), total body bone mineral content (BMC) for lean mass was reduced (p = .002). Multiple regression models adjusting for height, weight, and gender demonstrated an inverse relationship between total body fat mass and total body, lumbar, and ultradistal radius BMC and aBMD. The data suggest that fat mass substantially inhibits bone accrual in children with prior fracture. These children may require targeted interventions to increase bone mass during adolescence to achieve optimal peak bone mass and reduce the risk of osteoporosis later in life.

Peak bone mineral density, lean body mass and fractures

BACKGROUND

During childhood and adolescence, bone mass and lean body mass (LBM) increase till a plateau is reached. In this longitudinal and cross-sectional study, the age of reaching the plateau was evaluated for lumbar spine and total body bone mass measurements and lean body mass. The association between fractures and bone mineral density (BMD) was studied.

PATIENTS AND METHODS

We included 501 healthy participants, 141 males and 360 females, aged 13-29 years. Of these 90 had participated in a previous longitudinal study of 444 participants, aged 4-20 years (for the first measurement) and 198 participants, aged 8-25 years (for a second measurement). BMD and body composition were measured with dual energy X-ray absorptiometry (DXA). Volumetric BMD (bone mineral apparent density, BMAD) was calculated. All the data were used to determine the age of reaching the plateau.

RESULTS

The plateau for lumbar spine BMD, BMAD, total body BMD, bone mineral content and LBM was reached between 18 and 20 years of age in females and between 18 and 23 years in males. The prevalence of fractures was 37% in males and 28% in females. Total body BMD Z-score was significantly lower in all participants who had had a fracture (p<0.05), whereas lumbar spine BMD and BMAD was only significantly lower in females who had had fractures (p=0.007 and p<0.001, respectively). Mean lumbar spine BMAD Z-score at the previous measurement was significantly lower in the participants who had a first fracture between the last two measurements (p=0.04).

CONCLUSION

Peak BMD and peak LBM were attained between 18 and 20 years in females and between 18 and 23 years in males in this study using longitudinal and cross sectional data in the age range of 4 to 30 years. A significantly lower total body BMD was seen in participants who had had a fracture and a lower lumbar spine BMD and BMAD in females who had had a fracture. Lumbar spine BMAD Z-score seems to be a good predictor for future fractures.

Maximizing bone mineral mass gain during growth for the prevention of fractures in the adolescents and the elderly

Bone mass is a key determinant of fracture risk. Maximizing bone mineral mass during childhood and adolescence may contribute to fracture risk reduction during adolescence and possibly in the elderly. Although more than 60% of the variance of peak bone mass (PBM), the amount of bone present in the skeleton at the end of its maturation process, is genetically determined, the remainder is likely influenced by factors amenable to positive intervention, such as adequate dietary intake of dairy products as a natural source of calcium and proteins, vitamin D, and regular weight-bearing physical activity. Low calcium and vitamin D intakes are associated with negative effects on bone, including suboptimal PBM acquisition. As suggested by intervention studies, regular intake of dairy products may have positive and possibly sustained effects on bone mineral mass gain, contributing thereby to fracture risk reduction. Further evidence from intervention studies suggests that weight-bearing physical activities, such as jumping, may contribute to bone mineral mass gain in children. Optimizing PBM acquisition through dietary and physical exercise measures may represent a valuable primary method for the prevention of fractures.

A new link between skeleton, obesity and insulin resistance: relationships between osteocalcin, leptin and insulin resistance in obese children before and after weight loss

BACKGROUND

The skeleton is regarded recently as an endocrine organ that affects energy metabolism. However, there are very limited data available concerning the relationships between the osteoblast-derived hormone osteocalcin, weight status, adiponectin and leptin in obese humans, especially in children.

METHODS

We analyzed osteocalcin, adiponectin, leptin and insulin resistance (IR) index homeostasis model assessment (HOMA) in 60 obese and 19 age- and gender-matched normal weight children. Furthermore, these parameters were determined in 60 obese children after participating in an outpatient 1-year lifestyle intervention based on exercise, behavior and nutrition therapy.

RESULTS

Sixty obese children had significantly lower osteocalcin levels (26.8+/-0.8 ng ml(-1)) than 19 normal weight controls (32.2+/-2.3 ng ml(-1)). Boys (29.9+/-1.1 ng ml(-1)) showed significantly (P=0.046) higher osteocalcin levels compared with girls (26.4+/-1.2 ng ml(-1)). In stepwise multiple linear regression analysis adjusted for age, gender and pubertal stage, osteocalcin was significantly negatively related to leptin and HOMA, but not to adiponectin. Changes of osteocalcin in the course of 1 year correlated significantly negatively with changes of IR index HOMA (r=-0.25), standard deviation score-body mass index (SDS-BMI) (r=-0.33) and leptin (r=-0.50). Substantial weight loss in 29 obese children led to a significant increase in osteocalcin and a significant decrease in leptin and HOMA. In 31 obese children without substantial weight loss, osteocalcin levels did not change significantly in the course of 1 year.

CONCLUSION

Osteocalcin levels were lower in obese children and were related to IR and leptin both in cross-sectional and longitudinal analyses. Therefore, osteocalcin might be a new promising link between obesity and IR.

Official positions of the International Society for Clinical Densitometry (ISCD) on DXA evaluation in children and adolescents

Dual-energy X-ray absorptiometry (DXA) is the most widely used technical instrument for evaluating bone mineral content (BMC) and density (BMD) in patients of all ages. However, its use in pediatric patients, during growth and development, poses a much more complex problem in terms of both the technical aspects and the interpretation of the results. For the adults population, there is a well-defined term of reference: the peak value of BMD attained by young healthy subjects at the end of skeletal growth. During childhood and adolescence, the comparison can be made only with healthy subjects of the same age, sex and ethnicity, but the situation is compounded by the wide individual variation in the process of skeletal growth (pubertal development, hormone action, body size and bone size). The International Society for Clinical Densitometry (ISCD) organized a Pediatric Position Development Conference to discuss the specific problems of bone densitometry in growing subjects (9-19 years of age) and to provide essential recommendations for its clinical use.

Operative treatment of fractures in children is increasing. A population-based study from Finland

BACKGROUND

Epidemiological data on the incidence of surgical treatment of pediatric fractures are sparse. Our aim was to determine the incidence of in-hospital-treated fractures and of the surgical treatment of these fractures in children and adolescents.

METHODS

National Discharge Register data on pediatric fractures (in patients younger than the age of eighteen years) treated in the hospital in Finland between 1997 and 2006 were evaluated.

RESULTS

During the ten-year follow-up period, the incidence (per 100,000 persons) of fractures leading to hospitalization increased by 13.5% (from 319 in 1997 to 362 in 2006; p < 0.001). This change resulted mainly from an increase in the incidence of hospital-treated upper-extremity fractures (23% increase; from 189 in 1997 to 232 in 2006). The incidence of primary fracture surgery increased by 20% (from 237 in 1997 to 284 in 2006; p < 0.001). The incidences of surgery for upper-extremity, lower-extremity, and axial fractures increased by 28%, 3.9%, and 10.7%, respectively. Within the upper-extremity-fracture group, the incremental increase was mainly due to an increase in forearm fracture surgery (62% increase; from fifty-five in 1997 to eighty-nine in 2006) (p < 0.001).

CONCLUSIONS

Operative treatment of children's fractures has increased markedly during the last ten years. Evidence-based medical and economic data supporting this change in practice are sparse.

Overweight children have a greater proportion of fat mass relative to muscle mass in the upper limbs than in the lower limbs: implications for bone strength at the distal forearm

BACKGROUND

The influence of adiposity on upper-limb bone strength has rarely been studied in children, despite the high incidence of forearm fractures in this population.

OBJECTIVE

The objective was to compare the influence of muscle and fat tissues on bone strength between the upper and lower limbs in prepubertal children.

DESIGN

Bone mineral content, total bone cross-sectional area, cortical bone area (CoA), cortical thickness (CoTh) at the radius and tibia (4% and 66%, respectively), trabecular density (TrD), bone strength index (4% sites), cortical density (CoD), stress-strain index, and muscle and fat areas (66% sites) were measured by using peripheral quantitative computed tomography in 427 children (206 boys) aged 7-10 y.

RESULTS

Overweight children (n = 93) had greater values for bone variables (0.3-1.3 SD; P < 0.0001) than did their normal-weight peers, except for CoD 66% and CoTh 4%. The between-group differences were 21-87% greater at the tibia than at the radius. After adjustment for muscle cross-sectional area, TrD 4%, bone mineral content, CoA, and CoTh 66% at the tibia remained greater in overweight children, whereas at the distal radius total bone cross-sectional area and CoTh were smaller in overweight children (P < 0.05). Overweight children had a greater fat-muscle ratio than did normal-weight children, particularly in the forearm (92 +/- 28% compared with 57 +/- 17%). Fat-muscle ratio correlated negatively with all bone variables, except for TrD and CoD, after adjustment for body weight (r = -0.17 to -0.54; P < 0.0001).

CONCLUSIONS

Overweight children had stronger bones than did their normal-weight peers, largely because of greater muscle size. However, the overweight children had a high proportion of fat relative to muscle in the forearm, which is associated with reduced bone strength.

Metabolismo do cálcio na fenilcetonúria

A Fenilcetonúria é um erro inato do metabolismo do aminoácido fenilalanina. O tratamento é essencialmente dietético e envolve uma restrição severa no consumo de alimentos contendo aminoácido fenilalanina. Embora a alimentação seja complementada com fórmulas a fim de suprir as necessidades de vitaminas, minerais e aminoácidos essenciais, carências nutricionais ainda ocorrem. Isto se deve, principalmente, à restrição de fontes protéicas, que acarreta deficiência na ingestão de diversos nutrientes, dentre eles o cálcio. O cálcio possui importante relação com a formação mineral óssea. Estudos recentes demonstram que portadores de fenilcetonúria apresentam freqüentemente osteopenia e fraturas, sendo a maior incidência em crianças acima de 8 anos de idade. O rápido aumento da estatura, a dieta deficiente em cálcio e níveis de aminoácido fenilalanina elevados têm sido descritos como os principais fatores para a aquisição de massa óssea inadequada. A suplementação de cálcio em crianças saudáveis mostrou um efeito positivo sobre a aquisição de massa óssea na fase da pré-puberdade. Assim, torna-se relevante compreender a necessidade da suplementação de cálcio em pacientes fenilcetonúria, a fim de favorecer o desenvolvimento ósseo esperado.

Endocrine and musculoskeletal abnormalities in patients with Down syndrome

Down syndrome has a prevalence of one in 500 to one in 1,000 live births and is the most common cause of mental retardation. Most patients are treated in childhood and adolescence for mental or growth retardation. Studies that evaluate bone mass in Down syndrome are limited, and many are small case series in pediatric and adult populations who live either in the community or in residential institutions. Several environmental and hormonal factors contribute to low bone mineral density in such patients. Muscle hypotonia, low amounts of physical activity, poor calcium and vitamin D intakes, hypogonadism, growth retardation and thyroid dysfunction contribute to substantial impairments in skeletal maturation and bone-mass accrual that predispose these patients to fragility fractures. Here, we review indications and limitations of bone-mass measurements in children, summarize the endocrine and skeletal abnormalities in patients presenting with Down syndrome, and review studies that investigate therapeutic strategies for such patients.

Bone structure at the distal radius during adolescent growth

The incidence of distal forearm fractures peaks during the adolescent growth spurt, but the structural basis for this is unclear. Thus, we studied healthy 6- to 21-yr-old girls (n = 66) and boys (n = 61) using high-resolution pQCT (voxel size, 82 microm) at the distal radius. Subjects were classified into five groups by bone-age: group I (prepuberty, 6-8 yr), group II (early puberty, 9-11 yr), group III (midpuberty, 12-14 yr), group IV (late puberty, 15-17 yr), and group V (postpuberty, 18-21 yr). Compared with group I, trabecular parameters (bone volume fraction, trabecular number, and thickness) did not change in girls but increased in boys from late puberty onward. Cortical thickness and density decreased from pre- to midpuberty in girls but were unchanged in boys, before rising to higher levels at the end of puberty in both sexes. Total bone strength, assessed using microfinite element models, increased linearly across bone age groups in both sexes, with boys showing greater bone strength than girls after midpuberty. The proportion of load borne by cortical bone, and the ratio of cortical to trabecular bone volume, decreased transiently during mid- to late puberty in both sexes, with apparent cortical porosity peaking during this time. This mirrors the incidence of distal forearm fractures in prior studies. We conclude that regional deficits in cortical bone may underlie the adolescent peak in forearm fractures. Whether these deficits are more severe in children who sustain forearm fractures or persist into later life warrants further study.

Accounting for body size deviations when reporting bone mineral density variables in children

In a child, bone mineral density (BMD) may differ from an age-expected normal value, not only because of the presence of disease, but also because of deviations of height or weight from population averages. Appropriate adjustment for body size deviations simplifies interpretation of BMD measurements.

INTRODUCTION

For children, a bone mineral density (BMD) measurement is normally expressed as a Z score. Interpretation is complicated when weight or height distinctly differ from age-matched children. We develop a procedure to allow for the influence of body size deviations upon measured BMD.

METHODS

We examined the relation between body size deviation and spine, hip and whole body BMD deviation in 179 normal children (91 girls). Expressions were developed that allowed derivation of an expected BMD based on age, gender and body size deviation. The difference between measured and expected BMD was expressed as a HAW score (Height-, Age-, Weight-adjusted score).

RESULTS

In a second independent sample of 26 normal children (14 girls), measured spine, total femur and whole body BMD all fell within the same single normal range after accounting for age, gender and body size deviations. When traditional Z scores and HAW scores were compared in 154 children, 17.5% showed differences of more than 1 unit and such differences were associated with height and weight deviations.

CONCLUSION

For almost 1 in 5 children, body size deviations influence BMD to an extent that could alter clinical management.

Adiposity and TV viewing are related to less bone accrual in young children

OBJECTIVE

To examine the relation between baseline fat mass and gain in bone area and bone mass in preschoolers studied prospectively for 4 years, with a focus on the role of physical activity and TV viewing.

STUDY DESIGN

Children were part of a longitudinal study in which measures of fat, lean and bone mass, height, weight, activity, and diet were taken every 4 months from ages 3 to 7 years. Activity was measured by accelerometer and TV viewing by parent checklist. We included 214 children with total body dual energy x-ray absorptiometry (Hologic 4500A) scans at ages 3.5 and 7 years.

RESULTS

Higher baseline fat mass was associated with smaller increases in bone area and bone mass over the next 3.5 years (P < .001). More TV viewing was related to smaller gains in bone area and bone mass accounting for race, sex, and height. Activity by accelerometer was not associated with bone gains.

CONCLUSIONS

Adiposity and TV viewing are related to less bone accrual in preschoolers.

Eight-year clinical outcomes of long-term enzyme replacement therapy for 884 children with Gaucher disease type 1

OBJECTIVE

The goal was to analyze the clinical responses to enzyme replacement therapy with alglucerase or imiglucerase in a large international cohort of children with Gaucher disease type 1.

METHODS

Anonymized data from 884 children in the International Collaborative Gaucher Group Gaucher Registry were analyzed to determine the effects of long-term enzyme replacement therapy with alglucerase or imiglucerase on hematologic and visceral manifestations, linear growth, and skeletal disease. The parameters measured were hemoglobin levels, platelet counts, spleen and liver volumes, z scores for height and bone mineral density, and reports of bone pain and bone crises.

RESULTS

The median height z score for the study population was -1.4 at baseline. After 8 years of treatment, the median height approximated the median value for the normal population. Anemia, although not severe, was present in >50% of patients at baseline and resolved for all patients after 8 years of treatment. More than 50% of patients had platelet counts of <100000 platelets per mm3 at baseline, but >95% had platelet counts above this level after 8 years of treatment. Liver and spleen volumes decreased over 8 years of treatment. The mean bone mineral density z score was -0.34 at baseline, and values normalized within 6.6 years of treatment. Seventeen percent of patients reported a bone crisis before treatment and in the first 2 years of treatment, but no bone crises were reported after 2 years of enzyme replacement therapy. Few patients (2.5%) without bone crises before enzyme replacement therapy had a crisis after the start of treatment.

CONCLUSIONS

These longitudinal data quantitate the benefits of continuous enzyme replacement therapy with alglucerase/imiglucerase for children with Gaucher disease type 1. Within 8 years of enzyme replacement therapy, most clinical parameters studied became normal or nearly normal.

Epidemiology of osteoporosis

Osteoporosis represents a major public health problem through its association with fragility fractures. All osteoporotic fractures increase patient morbidity; however, fractures of the hip and vertebrae are also linked with significant mortality. The public health burden of osteoporotic fracture is likely to rise in future generations, due in part to an increase in life expectancy. Understanding the epidemiology of this disease is therefore essential in trying to develop strategies to help reduce this load. This chapter will review the epidemiology of osteoporosis, including the relationship between low bone mass and fracture. It will review the epidemiology of fractures, concentrating on the sites where the majority of age-related fractures occur. Finally it will discuss new developments in the assessment of fracture risk.

Bone mineral content and bone mineral density are lower in older than in younger females with Rett syndrome

Although bone mineral deficits have been identified in Rett syndrome (RTT), the prevalence of low bone mineral density (BMD) and its association with skeletal fractures and scoliosis has not been characterized fully in girls and women with RTT. Accordingly, we measured total body bone mineral content (BMC) and BMD using dual energy x-ray absorptiometry in a cross-sectional group of 50 females, aged 2-38 y, with RTT. Methyl-CpG-binding 2 (MECP2) mutations, skeletal fractures, and scoliosis were documented. The prevalence of BMC and BMD z scores < or-2 SD was 59 and 45%, respectively. Although absolute BMC and BMD increased significantly with increasing age, BMC, and BMD z scores were significantly lower in older than in younger females. The prevalence of fractures and scoliosis was 28 and 64%, respectively. Low BMD z scores were positively associated with fractures and scoliosis. Deficits in BMD were identified across a broad range of MECP2 mutations. This study identified associations among low BMD, fractures, and scoliosis, and underscored the need for better understanding of the molecular mechanisms of MECP2 in the regulation of bone mineral metabolism.

Fracture prediction and the definition of osteoporosis in children and adolescents: the ISCD 2007 Pediatric Official Positions

Osteoporosis in adults has been defined on the basis of densitometric criteria, but at present the term osteoporosis does not have a widely recognized definition in pediatrics. Consequently, the International Society for Clinical Densitometry (ISCD) 2007 Position Development Conference reviewed the literature describing the relationship between bone densitometric studies and fractures in apparently healthy children and adolescents, and prepared Official Positions regarding the definition of osteoporosis in children and adolescents. The ISCD Official Positions with respect to the above issues, as well as the rationale and evidence used to derive these positions, are presented here.

Dual energy X-ray absorptiometry interpretation and reporting in children and adolescents: the 2007 ISCD Pediatric Official Positions

The International Society for Clinical Densitometry Official Positions on reporting of densitometry results in children represent an effort to consolidate opinions to assist healthcare providers determine which skeletal sites should be assessed, which adjustments should be made in these assessments, appropriate pediatric reference databases, and elements to include in a dual energy X-ray absorptiometry (DXA) report. Skeletal sites recommended for assessment are the lumbar spine and total body less head, the latter being valuable as it provides information on soft tissue, as well as bone. Interpretation of DXA findings in children with growth or maturational delay requires special consideration; adjustments are required to prevent erroneous interpretation. Normative databases used as a reference should be based on a large sample of healthy children that characterizes the variability in bone measures relative to gender, age, and race/ethnicity, and should be specific for each manufacturer and model of densitometer and software. Pediatric DXA reports should provide relevant demographic and health information, technical details of the scan, Z-scores, and should not include T-scores. The rationale and evidence for development of the Official Positions are provided. Given the sparse data currently available in many of these areas, it is likely that these positions will change over time as new data become available.

Influence of birth size and body composition on bone mineral density in early adulthood: the PROGRAM study

BACKGROUND/OBJECTIVES

Low bone mineral density (BMD) may lead to osteoporosis and is associated with increased fracture risk. Associations between BMD and various factors have been reported. Our objective was to investigate whether birth size, lean body mass (LBM) and fat mass (FM) are determinants of BMD of the total body (BMD(TB)) and the lumbar spine (BMD(LS)).

METHODS

In the PROgramming factors for GRowth And Metabolism (PROGRAM) study of a cohort of 312 young adults aged 18-24 years, BMD(TB) and BMD(LS) were determined by dual-energy X-ray absorptiometry (DXA). Subsequently, differences in BMD(TB) and BMD(LS) were analysed in four subgroups: young adults born small for gestational age with short stature (SGA-S) or with catch-up growth (SGA-CU), or born appropriate for gestational age (AGA) with idiopathic short stature (ISS) or with normal stature (controls).

RESULTS

Adult weight, LBM, FM and weight gain during childhood were the main positive determinants for BMD(TB) in early adulthood, whereas birth size had no influence (adjusted R(2) = 0.50). Gender, adult weight, LBM, FM and weight gain were the significant determinants of BMD(LS). In the subgroups, after correction for age, gender and adult body size, the ISS group had a significantly lower BMD(TB) than controls but there was no difference in BMD(LS) between the subgroups.

CONCLUSIONS

Prenatal growth has no significant influence on BMD(TB) and BMD(LS) in early adulthood. Gender and postnatal growth, particularly weight gain, are the main positive determinants. To achieve a normal BMD in adulthood, healthcare workers should aim for a normal weight gain in children.

Healthy children with frequent fractures: how much evaluation is needed?

OBJECTIVE

We performed a case-control study to determine whether occult bone disease is associated with a history of frequent fractures in children.

METHODS

Healthy children with > or = 2 incidences of low-energy fractures were recruited (n = 68). Children with no history of fractures served as control subjects (n = 57). Food logs, activity surveys, physical examinations, laboratory tests, and dual-energy radiographic absorptiometry were used.

RESULTS

Bone mineral density z scores were significantly reduced in case subjects, compared with control subjects. Three case subjects (4.3%) and 1 control subject (1.8%) had bone mineral density z scores below the expected range. Of those 4 subjects, 2 had dairy avoidance and 2 had delayed puberty. An additional case subject had evidence of vitamin D deficiency. A significant number of subjects (20% of case subjects and 23% of control subjects) had idiopathic hypercalcuria, based on 24-hour urine collections. Among the case subjects, bone mineral density z scores were significantly lower for those with idiopathic hypercalcuria. Among the control subjects, the presence of idiopathic hypercalcuria did not affect bone mineral density. The case subjects with idiopathic hypercalcuria accounted for virtually all of the differences in bone mineral density between the case and control groups. Analysis of parathyroid hormone and 1,25-dihydroxy-vitamin D levels showed that children with frequent fractures and hypercalcuria had renal hypercalcuria, whereas children with no fractures and hypercalcuria had absorptive hypercalcuria.

CONCLUSIONS

We identified a significant association between a history of frequent fractures and hypercalcuria in children. We propose that the appropriate screening evaluation for children who present with a history of frequent fractures consists of a dietary history targeted at calcium and vitamin D intakes, a physical examination to assess for pubertal delay, and urinary calcium concentration/creatinine ratio determination to assess for hypercalcuria. Children with abnormalities in this screening should undergo dual-energy radiographic absorptiometry and appropriate evaluation.

Interactions between effects of estrogen receptor gene polymorphisms on BMD and experiences of the first spermorrhea in Chinese Han boys

OBJECTIVE

To study the interaction between polymorphisms of estrogen receptor (ER) gene and puberty on bone mineral density (BMD).

METHODS

One hundred and forty-six boys aged 13-17 years were divided into two groups according to their first spermorrhea. DNA was analyzed for Xba I and Pvu II genotypes by PCR-RFLP. BMD of the total body, forearm and lumbar spine was measured by dual-energy X-ray absorptiometry (DXA). The relationship between polymorphisms of ER gene and BMD in these two groups was analyzed.

RESULTS

The BMD at all sites in the spermorrhea group was significantly higher than that in the un-spermorrhea group. The independent contribution of ER genotypes to BMD at two pubertal stages was analyzed after adjusting co-variables. In the un-spermorrhea group, the BMD at distal 1/10 and 1/3 forearm of those carrying pp genotype was significantly higher than that of the non-carries, whereas in the spermorrhea group BMD in those carrying the same genotype was significantly lower than that in the non-carriers. Similar results were obtained by haplotype analysis. Multiple stepwise regression analysis showed that body weight, age and the first spermorrehea were the dominant determinants for BMD. BMD at forearm might be influenced by interaction between ER genotype and the first spermorrehea.

CONCLUSION

The polymorphisms of ER gene play a different role in BMD influenced by the first spermorrhea. Chinese boys carrying p or x allele should pay more attention to their bone mass.

Relationship of total body fat mass to bone area in New Zealand five-year-olds

Fat mass was recently shown to be a positive determinant of bone mass and size independently of lean mass in a birth cohort of British 9-year-olds. The present study was undertaken to investigate whether similar relationships are evident in younger, preschool children. Height and weight were measured, and a total-body dual-energy X-ray absorptiometric scan was performed on 194 preschool New Zealand children (81 girls, 113 boys) participating in the Dunedin birth cohort Family, Lifestyle, Activity, Movement, and Eating (FLAME) study close to their fifth birthday. Relationships of total-body fat mass and lean mass to total-body-less-head (TBLH) bone area and TBLH bone mineral content (BMC) were evaluated using linear regression. Girls had higher mean fat mass (3.9 vs. 3.2 kg) and lower lean mass (14.5 vs. 15.2 kg) than boys (P < 0.001), but their heights, weights, and TBLH bone area were similar. Although a given weight of lean tissue was associated with greater increases in TBLH area than a given weight of fat tissue, our results show that fat mass was an independent predictor of TBLH bone area (R (2 )= 0.79, P < 0.001) and TBLH BMC (R (2) = 0.74, P < 0.001) in data adjusted for socioeconomic status, ethnic group, lean mass, and height. We conclude that increased fat mass is associated with outward expansion of the TBLH skeletal envelope (wider bones) independently of height and lean mass in very young children.

Which bone mass measures discriminate adolescents who have fractured from those who have not?

This study of 415 adolescent children examined the association between four different measures of bone mass and prevalent fracture (N = 160 children). DXA measures and calcaneal ultrasound (but not radial ultrasound or metacarpal index) were associated with upper limb fracture, suggesting heel ultrasound is also a discriminator of fractures in children.

INTRODUCTION

The aim of the study was to describe the association between different measures of bone mass and prevalent fracture in adolescents.

METHODS

A total of 415 adolescents (150 girls and 265 boys), mean age 16.3 years were examined. Dual energy X-ray absorptiometry (DXA) measures were performed at hip, spine, radius and total body. Calcaneal bone ultrasound attenuation (BUA), speed of sound (SOS), and stiffness were assessed by a Sahara densitometer. Radial ultrasound SOS was assessed by a Sunlight 8000P machine. Metacarpal index was calculated from a left hand X-ray. Prevalent fractures were assessed by questionnaire.

RESULTS

A total of 160 adolescents (39%) reported at least one previous fracture (106 upper limb, 53 lower limb, one other for first fracture). Significantly lower DXA measures, heel BUA, and heel stiffness was observed in those with a history of upper limb fracture (all P < 0.05). Despite significant correlations between all the bone mass measures, radial ultrasound and metacarpal index did not discriminate those with fracture from those without. Similar associations were present for number of fractures. No bone measure was able to discriminate lower limb fracture.

CONCLUSIONS

Both calcaneal quantitative ultrasound and DXA are able to discriminate adolescents with a history of upper limb fracture from those without.

Proximal femur mechanical adaptation to weight gain in late adolescence: a six-year longitudinal study

The effect of weight gain in late adolescence on bone is not clear. Young women who consistently gained weight (n = 23) from 17 to 22 yr of age had increased BMD but a lack of subperiosteal expansion compared with stable weight peers (n = 48). Bone strength increased appropriately for lean mass in both groups but decreased relative to body weight in weight gainers, suggesting increased bone fragility in weight gainers.

INTRODUCTION

Weight gain leading to obesity often starts in adolescence, yet little is known about its effects on bone. We used longitudinal data to examine the effects of weight gain in late adolescence (from 17 to 22 yr of age) on proximal femur BMD, geometry, and estimates of bending strength.

MATERIALS AND METHODS

Participants were classified as either weight gainers (WG, n = 23) or stable weight (SW, n = 48) using a random coefficients model. Weight gainers had positive increases in weight (p < 0.05) at each clinic visit from age 17 onward. Proximal femur DXA scans (Hologic QDR 2000) taken annually from 17 to 22 yr of age were analyzed for areal BMD (g/cm(2)), subperiosteal width (cm), and bone cross-sectional area (CSA) at the proximal femoral shaft. Cortical thickness was measured, and section modulus (Z, cm(3)) was calculated as a measure of bone bending strength. Total body lean (g) and fat (g) mass were measured from DXA total body scans.

RESULTS

Over ages 17-22, height remained stable in both groups. Weight remained static in the SW group but increased 14% on average in the WG group (p < 0.05). After controlling for age 17 baseline values, WG had higher BMD (+2.6%), thicker cortices (+3.6%), and greater bone CSA (+2.3%). Increased BMD did not translate to greater increases in bone bending strength (Z). The SW group achieved similar gains in Z by greater subperiosteal expansion. Bone strength index (SI = Z/height) normalized for body weight remained constant in the SW group but decreased significantly in the WG group. In contrast, SI normalized to lean mass did not change over time in either group. Other variables including physical activity, nutrition, and hormone levels (estradiol, testosterone, cortisol) did not differ significantly between groups.

CONCLUSIONS

These data suggest that weight gain in late adolescence may inhibit the periosteal expansion known to normally occur throughout life in long bones, resulting in decreased bone strength relative to body weight.

Osteoporosis in children with cancer

As increasing numbers of childhood cancer patients are surviving, the long-term complications of the disease and its treatment have become ever more increasingly important. Reduced bone mineral density and increased fracture risk have been reported during and after treatment of children with cancer. The causes of osteoporosis are multifactorial. Among others, the disease itself, chemotherapy, irradiation and genetic susceptibility play a role. Bone mineral density in later life depends largely on the peak bone mass achieved in adolescence or young adulthood. Therefore, optimizing peak bone mass is of clinical importance. Preventive and therapeutic strategies, such as calcium and vitamin D supplementation, physical activity and bisphosphonates, are considered.

Impaired bone health in adolescents after liver transplantation

Long-term complications related to immunosuppressive medication are an important problem after liver transplantation (OLT). This study was carried out to evaluate the bone health and risk factors for osteoporosis and fractures in 40 pediatric liver transplant recipients. The results of 208 longitudinal bone mineral density (BMD) measurements were analyzed retrospectively. In addition, a dual-energy X-ray absorptiometry was performed to assess the bone mineral content more precisely and to detect subclinical vertebral fractures (VF). The median age of the patients was 14 years and mean postoperative follow-up 7.0 years. The results showed that over half (58%) had lumbar spine (LS) Z-score </=-1.0 and one-fifth (18%) had asymptomatic VF. LS Z-score tended to increase from the first year after OLT, but during puberty the bone mass gain was suboptimal and Z-scores decreased in some subjects. Patients with VF were older at the time of OLT (p = 0.002) and their LS Z-score was lower (p = 0.001). Children transplanted before 10 years of age had less VF (p = 0.004) and higher LS Z-score (p = 0.005) than older patients. In conclusion, adolescent liver recipients are prone to osteoporosis and prevention should be targeted especially to this age group.

Observational study of bone accretion during successful weight loss in obese adolescents

OBJECTIVE

To assess bone mineral content (BMC) among obese adolescents who lose weight during a critical period for bone accretion.

METHODS AND PROCEDURES

Whole body, lumbar spine, lower, and upper limb BMC were measured in 62 obese adolescents who completed an intensive 12-month weight loss trial. BMC was adjusted for height (z -scores) using data from a reference group of 66 adolescents (who were 18% overweight).

RESULTS

At baseline, the BMC of the obese group was higher than the reference group. During the 12-month weight loss program, unadjusted BMC increased among the obese adolescents, despite successful weight loss. After adjustment for height, whole body BMC did not change significantly from baseline to 12 months (mean +/- s.d.: 1.08 +/- 0.67 to 1.06 +/- 0.67, P = 0.7). Region-specific BMC-for-height however decreased for the lower (1.07 +/- 0.57 to 0.95 +/- 0.59, P < 0.001) and upper (1.29 +/- 0.56 to 1.18 +/- 0.57, P = 0.01) limbs, but lumbar spine BMC-for-height increased (0.14 +/- 1.06 to 0.40 +/- 0.94, P < 0.001). These changes were largely and independently explained by changes in lean and fat mass.

DISCUSSION

This study confirms that obese adolescents have high BMC for height and suggests that, unlike adults, their BMC continues to increase during weight loss and remains higher than the BMC of a reference group. After adjustment for growth-related changes, lower and upper limb BMC appears to decrease, while lumbar spine BMC appears to increase. These results suggest that to optimize the health benefits of weight loss among obese adolescents, their bone health should be better understood and addressed.

A structural approach to the assessment of fracture risk in children and adolescents with chronic kidney disease

Children with chronic kidney disease (CKD) have multiple risk factors for impaired accretion of trabecular and cortical bone. CKD during childhood poses an immediate fracture risk and compromises adult bone mass, resulting in significantly greater skeletal fragility throughout life. High-turnover disease initially results in thickened trabeculae, with greater bone volume. As disease progresses, resorption cavities dissect trabeculae, connectivity degrades, and bone volume decreases. Increased bone turnover also results in increased cortical porosity and decreased cortical thickness. Dual-energy X-ray absorptiometry (DXA)-based measures of bone mineral density (BMD) are derived from the total bone mass within the projected bone area (g/cm(2)), concealing distinct disease effects in trabecular and cortical bone. In contrast, peripheral quantitative computed tomography (pQCT) estimates volumetric BMD (vBMD, g/cm(3)), distinguishes between cortical and trabecular bone, and provides accurate estimates of cortical dimensions. Recent data have confirmed that pQCT measures of cortical vBMD and thickness provide substantially greater fracture discrimination in adult dialysis patients compared with hip or spine DXA. The following review considers the structural effects of renal osteodystrophy as it relates to fracture risk and the potential advantages and disadvantages of DXA and alternative measures of bone density, geometry, and microarchitecture, such as pQCT, micro-CT (microCT), and micro magnetic resonance imaging (microMRI) for fracture risk assessment.

Is adiposity advantageous for bone strength? A peripheral quantitative computed tomography study in late adolescent females

BACKGROUND

Whereas excess adiposity is presumed to be advantageous for the skeleton, studies investigating relations between bone strength and fat during youth have been equivocal.

OBJECTIVES

Relations of percentage body fat (BF) and bone strength indexes were assessed in late adolescent females, taking into consideration surrogates of muscle force [ie, muscle cross-sectional area (MCSA) and bone length]. Bone measurements in the normal- and high-fat groups were also compared.

DESIGN

Late adolescent females (n = 115; aged 18.2 +/- 0.4 y) participated in this cross-sectional study. Fat-free soft tissue mass, fat mass, and percentage BF were measured with the use of dual-energy X-ray absorptiometry. Tibial and radial peripheral quantitative computed tomography measurements were taken at the 4% (trabecular bone), 20% (cortical bone), and 66% (for measurement of MCSA) sites from the distal metaphyses.

RESULTS

Percentage BF was inversely related to radial cortical bone area, total bone cross-sectional area (CSA), cortical bone mineral content (BMC), periosteal circumference, and strength-strain index (SSI) (20% site; all P < 0.05). After control for MCSA and limb length, negative relations remained between percentage BF and radial measurements and were also observed at the tibia (20% site). Unadjusted bone measures were not different between groups. After control for MCSA, the high- compared with the normal-fat group had lower bone measures at the 20% site (cortical bone area and cortical BMC at the tibia, total bone CSA at the radius, and SSI at both the tibia and radius; P < 0.05 for all).

CONCLUSION

Excess weight in the form of fat mass does not provide additional benefits, and may potentially be negative, for adolescent bone.

Anthropometric, bone age, and bone mineral density changes after a family-based treatment for obese children

Our objective was to identify anthropometric, bone age, and bone mineral density (BMD) changes after a family-based treatment program for obese children. We conducted a longitudinal prospective study of 50 obese children (body mass index percentage [BMI%] > or =120%) aged 9.12 +/- 1.72 years (range 6-13) at baseline. A family-based treatment program, based on inadequate feeding style with progressive modification, aerobic physical exercise increase, active parental involvement, and the use of behavioural strategies (contracting, self-monitoring, social reinforcement), was developed during a 12-month period. Anthropometric data, lumbar spine (L2-L4) BMD by dual-energy X-ray absorptiometry, bone age (BA), bone age to chronological age ratio (BA/CA), and predicted adult height (PAH) were determined at baseline and 12 months. The statistical method used was analysis of variance and the paired Student t-test. Mean BMI standard deviation score (SDS) loss was -0.61 +/- 0.76 and BMI% loss was -5.17 +/- 9.73%. Height SDS significantly decreased, BA/CA ratio also decreased significantly, and PAH change was not significant. Lumbar spine BMD SDS and BMD% did not significantly change. A family-based treatment program was effective in obese children by reducing by 5% the BMI in 1 year and increasing the activity level. Treatment reduced growth velocity and delayed bone maturation rate without affecting PAH, reflecting a situation of previous early maturation. The treatment did not modify gaining bone mass.

Osteoporosis in children and adolescents

In recent years, the issue of low bone density in children and adolescents has attracted much attention. The classical definition of osteoporosis should be valid at any age, yet its practical applicability to children and adolescents remains a matter of debate and there is no consensus on a diagnosis based solely on the BMD value. The clinical relevance of uncomplicated low bone density in the young and its long-term consequences remain difficult to evaluate and there is only preliminary evidence that the BMD value is a predictor of fracture risk in growing subjects. Moreover, the interpretation of densitometric data in the young is difficult because the "normal" BMD values to be used for comparison are continuously changing with age, and in addition, depend on several variables, such as gender, body size, pubertal stage, skeletal maturation and ethnicity. Although Z-score values below -2 are generally considered a serious warning, most bone specialists make a diagnosis of osteoporosis in children and adolescents only in the presence of low BMD and at least one fragility fracture. The scope of this review is limited to presenting a picture of the available knowledge. The literature on fractures will be presented in detail, since fractures are one of the key elements in the debate. There are countless papers on fractures in childhood and adolescence, but very few of them attempt to identify fragility fractures, and still fewer develop the concept of osteoporosis in the young in relation to fractures. The different forms of primary and secondary osteoporosis, the more technical aspects of bone densitometry in pediatrics, and the delicate issue of treatment will be discussed only briefly.

Can BMD assessed by DXA at age 8 predict fracture risk in boys and girls during puberty?: an eight-year prospective study

This study reports on the association between DXA at age 8 and subsequent fractures in both male and female children. Bone densitometry at the total body and spine (but not hip) is a strong predictor of fracture (especially upper limb) during puberty.

INTRODUCTION

The aim of this study was to determine if prepubertal DXA can predict fracture risk during puberty.

MATERIALS AND METHODS

We studied 183 children who were followed for 8 yr (1460 person-years). Bone densitometry was measured at the total body, hip, and spine by DXA and reported as BMC, BMD, and bone mineral apparent density (BMAD). Fractures were self-reported at age 16 with X-ray confirmation,

RESULTS

There were a total of 63 fractures (43 upper limb). In unadjusted analysis, only total body BMD showed an inverse relationship with upper limb fracture risk (p = 0.03). However, after adjustment for height, weight, age (all at age 8), and sex, total body BMC (HR/SD, 2.47; 95% CI, 1.52-4.02), spine BMC (HR/SD, 1.97: 95% CI, 1.30-2.98), total body BMD (HR/SD, 1.67; 95% CI, 1.18-2.36), total body BMAD (HR/SD, 1.54; 95% CI, 1.01-2.37), and spine BMD (HR/SD, 1.53; 95% CI, 1.10, 2.22) were all significantly associated with upper limb fracture risk. Similar, but weaker associations were present for total fractures. There was a trend for overweight/obesity to be associated with increased upper limb fracture risk (HR, 1.53/category; p = 0.08).

CONCLUSIONS

Measurement of bone mass by DXA is a good predictor of upper limb fracture risk during puberty. Although we did not measure true BMD, the constancy of fracture prediction after a single measure suggests bone strength remains relatively constant during puberty despite the large changes in bone size.

The influence of lifestyle, menstrual function and oral contraceptive use on bone mass and size in female military cadets

Purpose

To determine the influence of menstrual irregularity, oral contraceptive use and other factors on bone mineral density (BMD) and bone size at different skeletal sites in 135 college-aged fit women.

Methods

Menstrual history, oral contraceptive use, exercise history, and nutritional factors including calcium, caffeine, and alcohol intake as well as tobacco use were determined by written survey. Height, weight and fitness levels were measured. Spine and hip BMD were measured by dual x-ray absorptiometry (DXA), calcaneus BMD by peripheral DXA, and tibial bone mineral content (BMC) and size by peripheral Quantitative Computed Tomography (pQCT).

Results

The mean age was 18.4 ± 0.8 years. Weight and prior exercise were positively related to BMD at most skeletal sites and to tibial bone size. Milk intake was positively related to calcaneal BMD, tibial BMC and cortical thickness. Fracture history was an important predictor of spine, hip and heel BMD. Women who had ≥ 10 menstrual cycles in the year prior to BMD measurement had higher BMD at all sites as well as a greater tibial mineral content and cortical thickness than women who had oligomenorrhea/amenorrhea (≤ 9 cycles in the prior year; all p < 0.05). Oral Contraceptive (OC) users had significantly lower BMD in the spine (p < 0.02) and calcaneus (p = 0.04), smaller tibial periosteal circumference and lower tibial mineral content (p < 0.02) than non-OC users.

Conclusion

In a population of fit, college-aged women, OC use and oligomenorrhea were associated with reduced BMD and bone size. Weight, as well as prior exercise and milk intake was positively related to bone density and size at some skeletal sites. Understanding these relationships would help improve skeletal health in young women.

Influence of sports participation and menarche on bone mineral density of female high school athletes

Weight-bearing exercise during adolescence may enhance peak bone mineral density (BMD) and reduce osteoporosis risk. The association of sports participation before and after menarche with areal BMD (by central DXA) was investigated in 99 female high school athletes (age 15.5+/-1.3 year). The frequency and duration of structured sports (school-based or other organized team) were assessed using an interviewer-assisted questionnaire. Overall, the average number of years of weight-bearing sport participation was 7.4+/-3.4 years; 72% of the athletes began sport participation before menarche. Training patterns and BMD were examined by tertiles of yearly weight-bearing sport participation (hours/year) before (WBpre), after (WBpost) menarche, and in total (WBtotal). After adjusting for chronological age, gynecological age, and BMI, compared to athletes in the WBtotal low tertile, athletes in the WBtotal high tertile had significantly greater BMD at the spine (p=0.009), total hip (p=0.03), trochanter (p=0.03), and total body (p=0.009). Similar patterns were found by WBpre or WBpost status, separately, with the exception of spine BMD which was significantly different across tertiles in WBpost only (p<0.01). While the number of years of participation was similar across tertiles of WBtotal, the number of months/year was significantly greater among athletes in the high tertile than athletes in the low tertile (9.2+/-3.4 month/year versus 5.0+/-2.9 month/year, respectively (p<0.001)). These results indicate that near year-round participation in structured weight-bearing sports during early adolescence may help young girls optimize bone mineral accrual during these critical years, and may decrease their risk of osteoporosis with advancing age.

Osteopenia and cancer in children and adolescents: the fragility of success

The attainment of a satisfactory peak bone mass, which is accomplished largely by the end of adolescence, is the best protection against excessive bone mineral loss in late adulthood. Factors that influence this process include age, race, sex, body size, pubertal status, diet, physical activity, and other lifestyle elements. Cancer and its treatment in children and teenagers adversely impact bone mineralization. In particular, chemotherapy (especially glucocorticosteroids and methotrexate) and cranial irradiation (apparently by reducing growth hormone secretion and by causing hypogonadotropic hypogonadism) interfere with normal bone turnover. Resorption often exceeds formation, resulting in net bone mineral loss and providing a rational basis for the use of antiresorptive drugs. Such osteopenia may be symptomatic, with pain and abnormal gait, and increases the risk of fractures several fold. The disorder is compounded by reduced physical activity, so programs to reduce this deficit are of measurable benefit. All of those engaged in the care of children and adolescents with cancer have an opportunity to improve the bone health of these young people and to limit their risk of developing osteoporosis and fragility fractures in adult life.

Coeliac disease and the risk of fractures - a general population-based cohort study

BACKGROUND

Earlier studies have suggested that untreated coeliac disease may be associated with osteoporosis, but results are contradictory for the risk of long-term fractures.

AIM

To study the association between coeliac disease and fractures.

METHODS

We used Cox regresson to examine the future risk of hip fracture and fracture of any type in more than 13 000 individuals with coeliac disease and 65 000 age- and sex-matched reference individuals in a general population-based cohort.

RESULTS

During follow-up, 1365 first hip fractures and 4847 fractures of any type occurred. Coeliac disease was positively associated with subsequent hip fracture (hazard ratio = 2.1; 95% CI = 1.8-2.4) (in children: hazard ratio = 2.6; 95% CI = 1.1-6.2) and fractures of any type (hazard ratio = 1.4; 95% CI = 1.3-1.5) (in children: hazard ratio = 1.1; 95% CI = 1.0-1.2). The absolute excess risk of hip fractures in children with coeliac disease was 4/100 000 person-years. Incidence ratios for hip fracture in individuals with CD were around two both prior to diagnosis of coeliac disease and afterwards; this risk increase remained 20 years after diagnosis of coeliac disease.

CONCLUSIONS

Individuals with coeliac disease, including children with coeliac disease, may be at increased risk of hip fracture and fracture of any type. Coeliac disease may be positively associated with long-term hip fracture risk.

UK reference data for the Hologic QDR Discovery dual-energy x ray absorptiometry scanner in healthy children and young adults aged 6-17 years

BACKGROUND

The use and correct interpretation of bone densitometry measurements in paediatric patients relies on the availability of appropriate reference data. Ideally, such data should be matched for sex, chronological age, height, weight, pubertal development and ethnicity.

AIM

To provide UK-specific reference data for the Hologic QDR Discovery dual-energy x ray absorptiometry (DXA) scanners.

METHODS

Healthy, Caucasian children aged 5-18 years were recruited from local schools, colleges, general practitioner surgeries and staff from the University of Manchester, Manchester, UK. Suitable participants had DXA measurements taken of the lumbar spine, hip and total body. Sex-specific reference centile curves for bone mineral apparent density (BMAD; spine and femoral neck) are provided, using the approach suggested by Mølgaard et al. to interpret the scans. LMS (lambda, mu, varsigma) tables for calculation of individual standard deviation scores (SDSs) were produced; a weblink is provided to these tables to allow calculation of an individual child's SDSs.

RESULTS

The total study population consisted of 442 participants (239 male). The total numbers of scans available for analysis were 431 of the lumbar spine, 426 of the total body and 393 of the proximal femur. Data are provided for clinical interpretation of the spine and femoral neck scans based on BMAD (g/cm3), which reduces the size dependence of DXA areal bone mineral density (g/cm2). The spine and total-body data are also presented for interpretation of results using the approach suggested by Mølgaard et al.

CONCLUSIONS

This article provides the first sex-specific and ethnicity-specific reference databases for UK, which should allow the clinician to assess bone mineral density in paediatric patients, measured by the Hologic QDR Discovery DXA scanner.

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.

Advances in the diagnosis and treatment of osteoporosis

Although severely low bone density is relatively rare in the pediatric population, it can be a significant problem in many patients with chronic illness. As peak bone formation occurs during adolescence, it is crucial that pediatricians and other care providers for this patient population recognize the significance of attainment of adequate bone. Dietary intake of vitamin D and calcium should be optimized, and correction of underlying causes of poor bone density should occur whenever possible. Assessment of bone density is difficult, as each technology available has problems, and none of the technologies are well-associated with fracture risk in pediatric patients. Once diagnosis of severely low bone density is established, treatment options are limited and poorly studied. The benefits of bisphosphonate therapy appear to outweigh the risks in patients with low bone density and frequent fragility fractures, and it appears that most improvement with bisphosphonates occurs within the first 2 to 4 years. Evidence, however, is emerging that once off therapy, bone turnover remains decreased for at least several years. During that time, improvements in bone density are decreased. Many questions remain regarding duration of therapy with bisphosphonate therapy and the long-term effects on the children who receive this medication. Anabolic therapies may become important in the future, but there is currently extremely limited information regarding their use in pediatrics.

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.