Ailsa Goulding

Bone Mineral Density in Girls with Forearm Fractures

In childhood, the most common site of fracture is the distal forearm. To determine whether young girls with these fractures have low bone density more commonly than fracture‐free controls, we measured bone density at the radius, spine, hip, and whole body and total body bone mineral content, lean tissue mass, and fat mass by dual‐energy X‐ray absorptiometry in 100 Caucasian girls aged 3–15 years with recent distal forearm fractures and 100 age‐ and gender‐matched controls. Bone density (age‐adjusted ratios of all cases:controls with 95% confidence intervals) was lower in cases at the ultradistal radius 0.963 (0.930–0.996), 33% radius 0.972 (0.945–0.999), lumbar spine 0.945 (0.911–0.980), hip trochanter 0.952 (0.918–0.988), and total body 0.978 (0.961–0.995). Moreover, osteopenia (defined as Z score below −1), was more common in cases than controls (p < 0.05) in the forearm, spine, and hip, with one third of fracture cases having low spinal density. Odds ratios (95% confidence intervals) for low bone density were: ultradistal radius, 2.2 (1.1–4.6); lumbar spine, L2‐L4, 2.6 (1.3–4.9); and femur trochanter, 2.0 (1.0–3.9). Fracture patients aged 8‐10 years weighed more (mean ± SD) than age‐matched controls (37.2 ± 8.0 kg vs. 32.5 ± 6.6 kg, p < 0.01) while older patients reported lower current and past calcium intakes than matched controls (p < 0.05). We conclude that low bone density is more common throughout the skeleton in girls with forearm fractures than in those who have never broken a bone, supporting the view that low bone density may contribute to fracture risk in childhood.

More Broken Bones: A 4‐Year Double Cohort Study of Young Girls With and Without Distal Forearm Fractures

Predictors of childhood fractures have not been investigated previously. This study was undertaken to determine whether a previous history of forearm fracture, low bone mineral density (BMD; both areal bone mineral density [aBMD, g/cm2] and volumetric bone mineral apparent density [BMAD, g/cm3]), or anthropometry, influence fracture risk in young girls. At baseline, two cohorts of girls, aged 3–15 years, were evaluated: 100 had recently broken a forearm (group 1) and 100 were fracture free (group 2). Four years later we restudied 170 of these girls (82 from group l and 88 from group 2). We now report the relationships of previous fracture history, baseline BMD (measured by dual‐energy X‐ray absorptiometry), baseline weight, and height to risk of new fracture. More new fractures occurred in group l (37 fractures in 24 girls) than in group 2 (8 fractures in 7 girls; p = 0.0007). The independent predictors for occurrence of a new fracture at any skeletal site in a multivariate model adjusting for age, weight, total body aBMD, and fracture history were previous fracture (hazard ratio [HR], 3.28; 95% CI, 1.41‐7.64); age (HR per l‐year increase, 0.91; 95% CI, 0.84‐0.99); total body aBMD (HR per l SD decrease, 1.92; 95% CI, 1.31‐2.81); and body weight (HR per l SD increase, 1.49; 95% CI, 1.06‐2.08). Girls with two risk factors together had substantially greater fracture risk: previous fracture and low spinal BMAD (HR, 9.4; 95% CI, 2.8‐32.0), previous fracture and high body weight (HR, 10.2; 95% CI, 2.8‐37.6), or previous fracture and low total body aBMD (HR, 13.0; 95% CI, 3.9‐43.1). We conclude that previous forearm fracture, low total body aBMD, low spinal BMAD, and high body weight each increase risk of new fractures within 4 years in young girls. Interventions to reduce the risk of fractures, particularly forearm fractures, in girls warrant further study.

Overweight and obese children have low bone mass and area for their weight

OBJECTIVES: To determine whether girls and boys categorized from body mass index (BMI) values as overweight or obese for their age have lower bone mineral content (BMC) or lower bone area in relation to total body weight than children of normal adiposity.DESIGN: Cross-sectional study in a university bone research unit.SUBJECTS: Two hundred girls and 136 boys aged 3–19 y recruited from the general population by advertisement.MEASUREMENTS: Total body BMC (g) and bone area (cm2) measured by dual energy X-ray absorptiometry (DXA) in relation to body weight (kg), lean tissue mass (kg) and fat mass (kg) in boys and girls of three different BMI percentile groupings: normal weight (BMI<85th percentile); overweight (85 to 94th BMI percentile); obese (≥95th BMI percentile).RESULTS: Obese children had higher BMC, bone area, and fat mass for chronological age than those of normal body weight (P<0.001). In spite of this the observed values for age-adjusted total body BMC and bone area relative to body weight were each lower than predicted values, in both overweight and obese children (2.5–10.1% less, P<0.05) than in children of lower adiposity.CONCLUSION: In overweight and obese boys and girls there is a mismatch between body weight and bone development during growth: their bone mass and bone area are low for their body weight.

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.

Plasma Leptin Values in Relation to Bone Mass and Density and to Dynamic Biochemical Markers of Bone Resorption and Formation in Postmenopausal Women

Abstract. After the menopause it has been noted that heavier women conserve bone better than those with lower body weight. The protective effect of obesity on bone mass has been ascribed to a high body fat content. The present study of 54 postmenopausal women was undertaken to determine whether circulating plasma levels of leptin, the newly described hormone produced in adipocytes, were correlated with age-adjusted total body bone mineral content (BMC) or bone mineral density (BMD), or with dynamic biochemical markers of bone resorption or of bone formation. Leptin values were strongly correlated with all measures of adiposity (P < 0.001). Age-adjusted values for BMC and BMD, respectively, were also positively correlated (P < 0.001) with body weight (r = 0.643, r = 0.502), total fat mass (r = 0.557, r = 0.510) and with plasma leptin concentrations (r = 0.480, r = 0.551), confirming a positive relationship between fat mass and bone mass. By contrast, no significant correlations were observed between plasma leptin and dynamic markers of bone resorption (urinary deoxypyridinoline/creatinine r =−0.105, hydroxyproline/creatinine r =−0.193) or formation (plasma osteocalcin r = 0.103). Because there was no evidence for an association between ciculating plasma levels of leptin and biochemical markers of either osteoclastic or osteoblastic activity we conclude it is unlikely that circulating leptin plays any significant direct role in controlling bone cell activity. Our results do not support the hypothesis that leptin mediates the bone-sparing effects of obesity.

Dynamic and static tests of balance and postural sway in boys: effects of previous wrist bone fractures and high adiposity

Ninety-three males aged 10-21 years undertook the Bruininks-Oseretsky balance test and two computerized posturography tests to evaluate the effects of (a) previous forearm fracture and (b) high body weight on balance and postural sway. Body composition was measured by dual energy X-ray absorptiometry. Fracture history did not affect balance measures. However, Bruininks-Oseretsky balance scores were negatively correlated with body weight, body mass index, percentage fat and total fat mass. Overweight subjects (n=25) had lower scores (P<0.05) than boys of healthy weight (n=47), supporting the view that overweight adolescents have poorer balance than those of healthy weight.

How Many Children Remain Fracture-Free During Growth? A Longitudinal Study of Children and Adolescents Participating in the Dunedin Multidisciplinary Health and Development Study

Abstract: While much is known regarding the incidence and pattern of fractures during growth, information is sparse as to how many children fracture repeatedly and how many remain fracture-free during growth. The Dunedin Multidisciplinary Health and Development Study, a birth cohort, whose members were questioned regularly throughout growth (at ages 5, 7, 9, 11, 13, 15 and 18 years) concerning injuries including fractures, has provided a unique opportunity to answer these questions. Life-table analysis showed that approximately half the children remained fracture-free throughout growth [girls 60.1%, (95% CI 54.7–65.0) and boys 49.3% (95% CI 44.0–54.4)]. Data on fracture history, for participants seen at every phase, was available for 601 members through to the age of 18 years (61.1% of the cohort seen at age 5 years). Two hundred and ninety-one of these 601 participants reported 498 fractures, with 172 sustaining a single fracture, and 119 more than one fracture (15.8% girls and 23.4% boys). The most common site of fracture was the wrist/forearm (24.1% of all fractures). We conclude that although bone fractures are a common adverse event in childhood, half of all children remain fracture-free throughout growth.

Early adiposity rebound: review of papers linking this to subsequent obesity in children and adults.

Purpose of reviewImproving our understanding of factors driving fat gain in young children should increase our ability to manage the rising problem of obesity. Accordingly, studies associating timing of adiposity rebound with later obesity are reviewed. Recent findingsInvestigations in many countries have confirmed that early adiposity rebound increases risk of high blood pressure and obesity in young adults. The magnitude of the effect can be substantial (>3 body mass index units at 18–21 years) for those undergoing early (<5 years of age) compared with late (>7 years of age) rebound. Early rebound is also associated with impaired glucose tolerance and diabetes in adulthood. Because adiposity rebound is determined using serial measurements of body mass index, the actual changes in body composition occurring during this time are obscured. Recent data show that changing body mass index during adiposity rebound is due to higher than average deposition of weight rather than slowing of the rate of height gain. Moreover, this increased weight gain occurs because of rapid deposition of fat rather than lean tissue, with early rebounders gaining fat mass at almost three times the rate of late rebounders. SummaryFuture work is needed to identify reasons for early adiposity rebound. Because high physical activity and low inactivity are associated with lower body fat during the period of adiposity rebound, studies should be undertaken to see whether stepping up activity can slow fat gain, delay the onset of adiposity rebound and lower adult obesity.

Gender differences in body fat content are present well before puberty

To determine whether gender differences in body fat could be detected in prepubertal children using dual energy X-ray absorptiometry (DEXA), body composition was measured in 20 healthy boys aged 3–8 y matched for age, height and weight with 20 healthy girls. Although boys and girls did not differ in age, height, weight, body mass index (BMI) or bone mineral content, the boys had a lower percentage of body fat (13.5±5.1 vs 20.4±6.1%, P<0.01), a lower fat mass (3.2±2.0 vs 4.9±3.1 kg, P<0.01), and a higher bone-free lean tissue mass (18.6±4.3 vs 17.0±3.5 kg, P<0.01) than the girls. Girls had approximately 50% more body fat than the boys. This is the first DEXA study to show that boys aged 3–8 y have less body fat than girls of similar age, height and weight. Thus, this technology demonstrates that significant gender differences in body composition are evident, well before the onset of puberty.

Sex Differences in Regional Body Fat Distribution From Pre- to Postpuberty

Few large studies have evaluated the emergence of sexual dimorphism in fat distribution with appropriate adjustment for total body composition. The objective of this study was to determine the timing and magnitude of sex differences in regional adiposity from early childhood to young adulthood. Regional fat distribution was measured using dual‐energy X‐ray absorptiometry (trunk and extremity fat using automatic default regions and waist and hip fat using manual analysis) in 1,009 predominantly white participants aged 5–29 years. Subjects were divided into pre (Tanner stage 1), early (Tanner stages 2–3), late (Tanner stages 4–5), and post (males ≥20 years and females ≥18 years) pubertal groups. Sexual dimorphism in trunk fat (adjusted for extremity fat) was not apparent until late puberty, when females exhibited 17% less (P < 0.001) trunk fat than males. By contrast, sex differences in waist fat (adjusted for hip fat) were apparent at each stage of puberty, the effect being magnified with age, with prepubertal girls having 5% less (P = 0.027) and adult women having 48% less (P < 0.0001) waist fat than males. Girls had considerably more peripheral fat whether measured as extremity or hip fat at each stage. Sex differences in regional adiposity were significantly greater in young adults than in late adolescence. Exclusion of overweight participants did not materially affect the estimates. Sexual dimorphism in fat patterning is apparent even prepubertally with girls having less waist and more hip fat than boys. The magnitude of the sex difference is amplified with maturation, and particularly from late puberty to early adulthood.