Forearm Bone Mineral Content Research Articles

Time Trends in Trajectories of Forearm Mineral Content and Bone Size during Childhood-Results from Cross-Sectional Measurements with the Same Apparatus Four Decades Apart.

Evidence suggests that single photon absorptiometry (SPA)-measured forearm bone mineral density (BMD) is lower in contemporary children in Malmö than it was four decades ago, but the fracture incidence in the at-risk population (all Malmö children) has been stable during the same period. The aim of this study was to evaluate if improvements in skeletal structure over time may explain this observation. In 2017-2018 we measured distal forearm bone mineral content (BMC; mg/cm) and periosteal diameter (mm) in 238 boys and 204 girls aged 7-15 using SPA. Based on the SPA measurements, we calculated forearm BMD (mg/cm2), bone mineral apparent density (BMAD, mg/cm3), section modulus, and strength index (BMAD × section modulus). The results were compared with those derived from measurements of 55 boys and 61 girls of the same ages using the same scanner in 1979-1981. We used log-linear regression with age, sex, and cohort as predictors to investigate differences in trait trajectories (trait versus age slopes [mean percent difference in beta values (95% confidence interval)]). SPA-measured forearm BMC was lower at each age in 2017-2018 compared to 1979-1981 (a mean age and sex adjusted relative difference of 9.1%), the forearm BMC trajectory was similar in 2017-2018 to that in 1979-1981 (reference) [0.0%/year (-1.0%, 1.0%)], while the 2017-2018 forearm periosteal diameter trajectory was steeper [1.1%/year (0.3%, 2.0%)]. Since bone size influences both BMD (BMC divided by scanned area) and mechanical characteristics, the forearm BMD trajectory was flatter in 2017-2018 [-1.1%/year (-2.0%, -0.2%)] and the forearm section modulus trajectory steeper [3.9%/year (1.4%, 6.4%)]. Forearm strength index trajectory was similar [1.8%/year (-0.5%, 4.1%)]. The lower SPA-measured forearm BMD trajectory in contemporary children compared to four decades ago may be offset by changes in forearm bone structure, resulting in similar overall bone strength. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Reference Ranges for Bone Mineral Content and Density by Dual Energy X-Ray Absorptiometry for Young Children.

Assessment of bone health in young children has been hampered by limited reference values for bone mineral content (BMC) and areal bone mineral density (aBMD) by dual energy X-ray absorptiometry (DXA). To identify age, sex, and population ancestry effects on BMC and aBMD and develop smoothed reference ranges for BMC and aBMD in young children. To quantify precision of bone measurements and influence of height-for-age Z-scores on bone Z-scores. We recruited 484 healthy children ages 1 to 2 years or 4.5 to 5 years at 2 clinical centers, who were seen once or up to 7 times over a 3-year period. Lumbar spine, distal forearm, and whole-body subtotal (ages ≥ 3 years) BMC and aBMD were measured by DXA. These data were combined with data from the Bone Mineral Density in Childhood Study from children ages 5 to 8.9 years to create the smoothed reference curves. For 1- to 5-year-olds, BMC and aBMD at all skeletal sites increased with age. Age trends differed by sex for BMC and aBMD of the spine, distal one-third radius, ultradistal radius, and by ancestry (Black vs non-Black) for all measures. BMC and aBMD precision (% coefficient of variation) ranged from 1.0% to 4.4%. Height Z-scores were positively associated with bone Z-scores and accounted for 4% to 45% of the variance. We demonstrate the feasibility of bone density measurements in young children and provide robust reference ranges and stature adjustments for calculation of bone Z-scores at multiple skeletal sites to enable bone health assessments.

Associations of Maternal Serum Perfluoroalkyl Substances Concentrations with Early Adolescent Bone Mineral Content and Density: The Health Outcomes and Measures of the Environment (HOME) Study.

Background:Per- and polyfluoroalkyl substances (PFAS) may impair bone accrual and strength via endocrine disruption and nuclear receptor agonism, but human studies are primarily of adults or cross-sectional.Objectives:We assessed associations of individual PFAS and their mixture during pregnancy with child bone mineral content (BMC) and areal bone mineral density (aBMD) at age 12 y.Methods:Among 206 mother–child pairs enrolled in a prospective cohort (2003–2006), we quantified perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorohexane sulfonic acid (PFHxS), and perfluorooctane sulfonic acid (PFOS) in maternal serum collected during gestation or delivery. When children were age 12 y, we performed dual energy X-ray absorptiometry and calculated BMC, aBMD, and bone mineral apparent density (BMAD) -scores for six skeletal sites. We estimated covariate-adjusted -score differences per doubling of individual PFAS using linear regression and assessed the PFAS mixture using quantile g-computation and Bayesian kernel machine regression. We explored whether associations were modified by child’s sex or mediated by whole-body lean mass.Results:In covariate-adjusted models, we found that higher maternal serum concentrations of PFOA, PFNA, and the PFAS mixture were associated with lower total hip and forearm (one-third distal radius) BMC -scores in children. Differences in forearm BMC -scores were [95% confidence interval (CI): , 0.01] and (95% CI: , ) per doubling of PFOA and PFNA, respectively, and (95% CI: , ) per quartile increase in the PFAS mixture. Child’s sex modified PFOA associations for some skeletal sites; for example, differences in spine BMAD -score per doubling were (95% CI: , ) among males and 0.07 (95% CI: , 0.30) among females (modification ). Except for PFNA among females, these associations were not mediated by whole-body lean mass.Discussion:Maternal PFAS concentrations during pregnancy may be associated with lower bone mineral accrual and strength in early adolescence. https://doi.org/10.1289/EHP9424

Arachidonic acid status negatively associates with forearm bone outcomes and glucose homeostasis in children with an overweight condition or obesity.

Long-chain polyunsaturated fatty acids are implicated in musculoskeletal health in adults. This study examined whether fatty acid status relates to bone health outcomes in children with overweight condition or obesity (body mass index z score, 3.1 ± 0.1; age, 9.0 ± 0.2 years; n = 108). Nondominant forearm bone density (distal one-third), geometry (4% site), and soft tissue composition (66%) were assessed using dual-energy X-ray absorptiometry and peripheral quantitative computed tomography. Red blood cell (RBC) fatty acid profile and indices of glucose homeostasis were measured. Differences in outcomes among RBC arachidonic acid (AA, C20:4n-6) tertiles were tested using mixed-model ANOVA. Ultra-, mid-, and total-distal forearm bone mineral content, adjusted for sex, age, percentage body fat, race, and forearm length, were 10% to 13% greater in children in the first AA tertile relative to the third. Children in the second tertile had the highest bone cross-sectional area and estimated strength at the 66% radius. Muscle cross-sectional area was 15% lower in the third tertile compared with the first, along with higher fasting insulin concentrations (27%) and homeostasis model of assessment estimate of insulin resistance (31%). Higher RBC AA status aligns with deficits in forearm bone mass, geometry, and muscle mass in children with excess adiposity and early signs of insulin resistance. Novelty Higher arachidonic acid status is associated with lower forearm bone mass in children with overweight condition or obesity. Children with higher arachidonic acid status had increased fasting insulin concentrations and indices of insulin resistance.

Long‐chain Polyunsaturated Fatty Acid Status Associates with Bone Mass in Overweight and Obese Children

Children who are obese are at increased risk of fractures. However, linkages to possible nutritional imbalances are unclear. Experimental studies suggest long‐chain polyunsaturated fatty acids (LCPUFA) such as arachidonic acid (AA C20:4 n6) modulate bone mass in a biphasic manner, yet it is uncertain whether this is observed in humans. This study examined the relationship between LCPUFA status and bone mass in overweight and obese (OvOb) children. Participants (n=119, 9.28 ± 1.89 y, BMI‐z 3.03 ± 1.02) were assessed for bone mass with DXA (Hologic Discovery). Fatty acid profile was measured in red blood cells (RBC) using gas chromatography. A generalized linear model was used to determine relationships between LCPUFA in RBC and bone outcomes with adjustments for Tanner stages and BMI. Saturated fatty acids palmitate (C16:0) and stearate (C18:0) inversely related to lumbar spine bone mineral density (r=‐0.18 and ‐0.22 respectively, p<0.05); while the omega‐3 fatty acid α‐linoleneate (ALA, C18:3 n3) positively related to whole body, total hip, ultra‐distal and mid forearm bone area, mineral content (BMC) and density (r=0.21 to 0.31, p<0.05). When children were divided into three groups by AA tertiles (cutoffs by 33rd and 67th percentile of % total FA) and compared with MIXED model ANOVA, those in the second tertile had greater forearm bone area and BMC than those in the first or third tertiles (Table 1), indicating higher AA levels may not confer additional benefits in bone growth and mineral accrual. These data suggest LCPUFA may play important roles in modulating bone mass during growth in OvOb children. 1st tertile (n=39) [4.67‐7.51%] 2nd tertile (n=35)[7.52‐ 8.42%] 3rd tertile (n=45)[8.44‐14.06%] Ultra‐dista Area (cm2) 4.09 ± 0.64a 4.67 ± 0.67b 4.29 ± 0.63a BMC (g) 1.32 ± 0.05 1.51 ± 0.09 1.38 ± 0.07 Mid Area (cm2) 7.50 ± 0.47ab 9.21 ± 0.55a 7.75 ± 0.32b BMC (g) 3.05 ± 0.22a 4.02 ± 0.34b 3.31 ± 0.19a 1/3 distal Area (cm2) 4.33 ± 0.10a 4.74 ± 0.10b 4.38 ± 0.06a BMC (g) 2.11 ± 0.09 2.43 ± 0.13 2.28 ± 0.09

Vitamin D Status is Associated With Bone Mineral Density and Bone Mineral Content in Preschool-Aged Children

This study examined the associations between vitamin D status, bone mineral content (BMC), areal bone mineral density (aBMD), and markers of calcium homeostasis in preschool-aged children. Children (n = 488; age range: 1.8–6.0 y) were randomly recruited from Montreal. The distal forearm was scanned using a peripheral dual-energy X-ray absorptiometry scanner (Lunar PIXI; GE Healthcare, Fairfield, CT). A subset (n = 81) had clinical dual-energy X-ray absorptiometry (cDXA) scans (Hologic 4500A Discovery Series) of lumbar spine (LS) 1–4, whole body, and ultradistal forearm. All were assessed for plasma 25-hydroxyvitamin D [25(OH)D] and parathyroid hormone concentrations (Liaison; Diasorin), ionized calcium (ABL80 FLEX; Radiometer Medical A/S), and dietary vitamin D and calcium intakes by survey. Age (p < 0.001) and weight-for-age Z-score (p < 0.001) were positively associated with BMC and aBMD in all regression models, whereas male sex contributed positively to forearm BMC and aBMD. Having a 25(OH)D concentration of >75 nmol/L positively associated with forearm and whole body BMC and aBMD (p < 0.036). Sun index related to (p < 0.029) cDXA forearm and LS 1–4 BMC and whole-body aBMD. Nutrient intakes did not relate to BMC or aBMD. In conclusion, higher vitamin D status is linked to higher BMC and aBMD of forearm and whole body in preschool-aged children.

Growth from birth to adulthood and peak bone mass and density data from the New Delhi Birth Cohort

Growth in early life may predict adult bone health. Our data showed that greater height and body mass index (BMI) gain in utero and infancy are associated with higher peak bone mass, and greater BMI gain in childhood/adolescence with higher peak bone density. These associations are mediated by attained adult height and BMI. To study the relationship of height and BMI during childhood with adult bone mineral content (BMC), areal density (aBMD) and apparent density (BMAD, estimated volumetric density). Participants comprised 565 men and women aged 33-39 years from the New Delhi Birth Cohort, India, whose weight and height were recorded at birth and annually during infancy (0-2 years), childhood (2-11 years) and adolescence (11 years-adult). Lumbar spine, femoral neck and forearm BMC and aBMD were measured using dual X-ray absorptiometry; lumbar spine and femoral neck BMAD were calculated. Birth length, and height and height gain during infancy, childhood and adolescence were positively correlated with adult BMC (p≤0.01 all sites except birth length with femoral neck). Correlations increased with height from birth to 6 years, then remained constant for later height measurements. There were no associations with BMAD. BMI at birth, and during childhood and adolescence was also positively correlated with BMC (p < 0.01 all sites). BMI at 11 years, and BMI gain in childhood and adolescence, were correlated with aBMD and BMAD (p < 0.001 for all); these correlations strengthened with increasing age of BMI measurement. The associations with height and BMI in early life became non-significant after adjustment for adult height and BMI. Greater skeletal growth and BMI gain in utero and during infancy are associated with higher peak BMC, and greater BMI gain in childhood and adolescence is associated with higher peak aBMD and BMAD. These associations are mediated by the attainment of adult height and BMI, respectively.

Whole Body Vibration Increases Hip Bone Mineral Density in Well-Trained Cyclists

Road cycling, a non-weight bearing endurance activity is associated with lower than expected bone mineral density (BMD) in its participants.Whole body vibration (WBV) has been shown to have therapeutic potential in increasing BMD in groups who have an elevated risk of fracture, yet the effects of WBV training have not been examined in road cyclists. PURPOSE: To determine the effects of ten weeks of WBV training, on the bone health in a group of well-trained road cyclists. METHODS: Nineteen road cyclists were randomly assigned to either a WBV training intervention (n=11), three times per week, ten minutes per session, for ten weeks, or a control cycling group (n=8) who did not add WBV to their training. Both groups continued with their normal cycling training during the study period. The cyclists were matched for age, height and weight with 19 sedentary subjects. At baseline, all participants underwent Dual X-ray Absorptiometry scans to measure site specific and regional BMD, bone mineral content (BMC) and lean and fat tissue; calcium intake and training history (for 19 cyclists) were also assessed. All cyclists were reassessed after ten weeks of training. RESULTS: At baseline, cyclists had lower hip (0.76±0.19 vs. 1.00±0.61g.cm-2, p<0.0001), pelvis (1.18±0.16 vs. 1.65±0.57 g.cm-2, p=0.002) and higher head BMD (2.41±0.41 vs. 1.82±0. 60g.cm-2, p=0.001) than sedentary control subjects. After the ten week WBV intervention, hip BMD increased significantly in the vibration cycling group (0.67±0.12 to 0.97±0.11 g.cm-2, p<0.0001) but not in the cycling control group. Ulna BMC (6.87±1.22g to 6.95 ± 1.23g, p=0.04) and radius BMC (10.37±1.70 to 10.52±1.70g, p=0.006) increased significantly in the vibration cycling group, but not in the control cyclists. CONCLUSION: Ten weeks of WBV training offers an intermittent alteration of force, displacement and acceleration and increases hip BMD and forearm BMC in road cyclists who have lower than normal bone mass and an increased fracture risk because of their greater risk of falling consequent to the nature of their sport.

Tracking of bone mass and density during childhood and adolescence.

Whether a child with low bone mineral density (BMD) at one point in time will continue to have low BMD, despite continued growth and maturation, is important clinically. The stability of a characteristic during growth is referred to as "tracking." We examined the degree of tracking in bone mineral content (BMC) and BMD during childhood and adolescence and investigated whether tracking varied according to age, sexual maturation, and changes in growth status. We conducted a longitudinal study with measurements at baseline and annually for 3 yr. The Bone Mineral Density in Childhood Study was conducted at five clinical centers in the United States. A total of 1554 girls and boys, ages 6-16 yr at baseline, participated in the study. Whole body, spine, hip, and forearm BMC and BMD were measured by dual-energy x-ray absorptiometry, and age-, sex-, and race-specific Z-scores were calculated. Deviation from tracking was calculated as the Z-score at yr 3 minus baseline. Correlations between Z-scores at baseline and yr 3 ranged from 0.76-0.88. Among children with a Z-score below -1.5 at baseline, 72-87% still had a Z-score below -1 after 3 yr. Age, sexual maturation, and deviations in growth status (P < 0.01) were associated with deviation from tracking; however, tracking was strongly evident even after adjusting for the effects of age, maturation, and growth. Bone density showed a high degree of tracking over 3 yr in children and adolescents. Healthy children with low bone density will likely continue to have low bone density unless effective interventions are instituted.

Skeletal Benefits of Pre-Menarcheal Gymnastics Are Retained After Activity Cessation

Mechanical loading during childhood and adolescence may yield skeletal benefits that persist beyond activity cessation and menarche. At 1 year pre- and 2 years post-menarche, nondominant forearm areal bone mineral density (aBMD), bone mineral content (BMC) and projected area (area) were compared in gymnasts (n = 9), ex-gymnasts (n = 8) and nongymnasts (n = 13). At both observations, gymnasts and ex-gymnasts had higher forearm aBMD, BMC and area than nongymnasts. Gymnasts had higher postmenarcheal means than ex-gymnasts for all three parameters. Childhood mechanical loading yields skeletal advantages that persist at least 24 months after loading cessation and menarche. Continued postmenarcheal loading yields additional benefit.

Effects of 8 months of twice-weekly high versus low intensity whole body vibration on risk factors for hip fracture in postmenopausal women: A randomized controlled trial

INTRODUCTION Whole body vibration (WBV) may improve bone mass and reduce fall risk in postmenopausal women at risk of hip fracture, however, the minimum effective dose and relative efficacy of high versus low intensity vibration, are unknown. METHODS Forty-seven postmenopausal women were randomised to control, low intensity (LV) or high intensity (HV) vibration. At baseline and follow-up, biometrics, whole body, proximal femur (PF), lumbar spine (LS) and forearm bone mineral content (BMC), bone mineral density (BMD), LS area, FN area, cortical width, index of bone strength, cross sectional moment of inertia (XR36, Norland), calcaneal broadband ultrasound attenuation (BUA) (QUS-2, Quidel), and functional muscle (chair rise, wall squat) and balance (single leg stance, tandem walk) performance were tested. Dietary calcium was determined via questionnaire and FoodWorks analysis (2007, Xyris, Brisbane). Current and historical bone-relevant physical activity was determined using the BPAQ (1). Treatment groups attended supervised WBV sessions twice weekly for 8 months (LV - 1 x 15 minute session at 30Hz, 0.2g; HV - 2 x 3 minute sessions at 12.5 Hz, ~1g). Treatment effects were examined by repeated measures ANOVA and multiple regression analyses controlling for age, weight, height, calcium consumption and physical activity. RESULTS No significant between-group effects were found for any measure, however, trends were evident and within group effects were observed. Significant bone loss occurred at the hip and spine in control (p=0.02) but not WBV groups. Wall squat time (muscle strength/endurance) and single leg stance (static balance) improved in the HV group (p=0.004) and a similar trend was evident for the LV group but not controls. A significant difference in calcaneal ultrasound between control and HV groups at baseline disappeared at follow-up as a result of bone loss in controls and gain in the HV group. CONCLUSIONS Findings suggest that twice-weekly WBV cannot entirely prevent age-related skeletal loss, but that loss may be considerably muted. Muscle and balance function can be improved with very minimal exposure to high intensity WBV. Findings have important clinical implications for groups at high risk of hip fracture who are unable or unwilling to adopt traditional therapeutic options. 1 Weeks BK and Beck BR: The BPAQ: A bone-specific physical activity assessment instrument. Osteoporosis International, 19(11):1567-1577, 2008.

Effect of Calcium Intake, Tennis Playing, and Body Composition on Bone-Mineral Density of Brazilian Male Adolescents

In this prospective, cross-sectional study male adolescent tennis players (44) and nonathletic controls (32) were evaluated to determine the effects of physical activity, dietary nutrient intakes, sexual maturation, and body composition on bone-mineral density (BMD). Dietary nutrient intakes and physical activity expenditure were estimated by 4-d diaries. Total body composition, bone-mineral content (BMC), and BMD (L1-L4, femur, and nondominant forearm) were assessed by dual-energy X-ray absorptiometry. Tennis players had significantly greater lean body mass (mean [SEM] 50.6 [1.6] kg vs. 45.1 [1.7] kg, p = .022), trochanter BMD (1.0 [0.02] g/cm2 vs. 0.9 [0.03] g/cm2, p = .032), and dominant forearm BMC (173.7 [7.4] g vs. 146.5 [9.3] g) but lower BMD in the nondominant forearm (0.7 [0.02] g/cm2 vs. 0.8 [0.03] g/cm2, p = .028). Daily average calcium intake was below the recommendation in both groups. No correlation was found between BMD and calcium intake and exercise. Lean body mass was the best predictor of BMD and BMC for both tennis players and controls (R2 = .825, .628, and .693 for L1-L4, total femur, and nondominant forearm, respectively). Based on these results the authors conclude that lean body mass is the best predictor of BMD and BMC for both tennis players and others. Tennis exerts a site-specific effect, and training should focus on ways minimize this effect. Although calcium intake showed no effect on BMD, nutrition education for young athletes should focus on promoting a balanced diet, providing energy and nutrients in adequate amounts.

Adverse effects of antiepileptic drugs on bone mineral density in children

Bone mineral content (BMC) or density (BMD) may be decreased in children with epilepsy either as a consequence of the epilepsy, the condition that caused the epilepsy or the treatment for epilepsy. This paper investigates the effects of antiepileptic drugs (AEDs) on BMD in children. A systematic search of Pubmed resulted in 14 papers that described changes in BMD in children on AEDs. For phenytoin, one study failed to show a decrease in femur BMD, whereas another study reported a decrease in total body and spine BMD, but only with the use of phenytoin for > 2 years. With phenytoin combined with a ketogenic diet, a decrease in forearm BMC was seen. For phenobarbital, one study showed a decrease in spine and total body BMD, but only among those who had used phenobarbital for > 2 years. Six studies were available for carbamazepine, and none of these showed a decrease in BMD in any skeletal site. For valproate, results were diverse; two studies reported a decrease in spine BMD, whereas two other studies did not. Two studies reported a decrease in hip BMD with valproate, whereas one did not. All three studies on forearm BMD in users of valproate described a decrease. Three studies reported an improvement in BMC with vitamin D supplementation in children on AEDs. No reports on changes in BMD among users of newer AEDs are available. In conclusion, more evidence is needed for the effects on BMD in children, especially for newer AEDs. The available studies have all been cross-sectional, and longitudianal studies are needed along with studies on potential interventions in children with decreased BMD.

Forearm bone geometry and mineral content in UK women of European and South-Asian origin

Ethnic variation in areal bone mineral density (BMD) has been well documented. Such variation may, however, reflects differences in bone geometry rather than volumetric BMD (vBMD). The aim of the study was to compare bone geometry, mineral content (BMC) and vBMD in two ethnic groups, and study the influence of body size, physical activity, reproductive variables, 25 hydroxy-vitamin D (25(OH)D) and parathormone (PTH) status on any observed differences. The data were from a population-based, cross-sectional survey of peak bone mass in South Asian and European women, the population consisted 230 pre-menopausal South Asian ( n = 118, mean age 28.6 ± 4.6 years) and European ( n = 112, mean age 30 ± 4.3 years) women of UK origin. Women who participated completed an interviewer assisted questionnaire, had blood taken for assessment of 25(OH)D and PTH and had measurements of their distal (4%) and diaphyseal (50%) radius geometry, BMC and vBMD using peripheral quantitative computed tomography. At the 50% radius, South Asians had lower vBMD ( p < 0.001), BMC ( p < 0.001), cortical area ( p < 0.001), cortical thickness ( p < 0.001), cross-sectional area ( p = 0.04) and increased medullary area ( p < 0.04). Cross-sectional muscle area and stress strain index, however, were not different. Adjustment for age, height and weight attenuated, the difference in cross-section area but did not account for any of the other observed differences. Further adjustment for reproductive variables a physical activity index, 25(OH)D and PTH, attenuated ethnic differences in cortical BMC, area and thickness which became non-significant; however, ethnic differences in cortical vBMD and medullary area persisted. At the 4% site, after adjusting for age, height and weight, there was no difference in total area, total or trabecular vBMD between ethnic groups. After further adjustment for physical activity, reproductive variables, 25(OH)D and PTH, trabecular vBMD was higher in the South Asians. In conclusion, there are differences in bone geometry, BMC and vBMD at the radial diaphysis between UK South Asians and Europeans which are not explained by differences in body size. Polar stress-strain index was similar, however, suggesting no important differences in bone strength.

Peripheral Bone Mineral Density and Different Intensities of Physical Activity in Children 6–8 Years Old: The Copenhagen School Child Intervention Study

This study aimed to evaluate the association between objectively measured habitual physical activity and calcaneal and forearm bone mineral density (BMD, g/cm(2)), one mechanically more loaded and one less loaded skeletal region, in children aged 6-8 years. BMD was measured in 297 boys and 265 girls by peripheral dual-energy X-ray absorptiometry in the forearm and calcaneus. An accelerometer registered the level of physical activity during 4 days (2 weekdays and the weekend). Weight, height, and skinfold thickness were measured. In order to establish thresholds (count . min(-1)) for bone-stimulating physical activity, we evaluated different definitions of vigorous physical activity. The boys had 3.2% higher distal forearm bone mineral content (BMC, P < 0.001) and 4.5% higher distal forearm BMD (P < 0.001) than the girls. They also carried out 9.7% more daily physical activity and spent 14.6-19.0% more time in vigorous physical activity (all P < 0.05) compared to the girls. In contrast, the girls had 3.8% higher calcaneal BMC (P < 0.01) and 2.5% higher calcaneal BMD (P < 0.05) than the boys. Both calcaneal and forearm BMD were significantly related to total time of daily physical activity as well as with intense physical activity above all the chosen cut-off points (all P < 0.05). The beta value for mean count . min(-1) physical activity was significantly lower than that for all the chosen cut-off points of vigorous activity both for calcaneal and distal forearm BMD. This study suggests that both habitual daily physical activity and amount of vigorous physical activity in children aged 6-8 years are associated with appendicular BMD.

Case‐control study of breast milk calcium in mothers of children with and without nutritional rickets

Abstract Aim: Despite similarly low calcium intakes and normal vitamin D status, only some Nigerian children develop nutritional rickets. We hypothesized that mothers with children who had developed rickets might have lower breast‐milk calcium concentration than mothers with normal children and compared the breast‐milk calcium concentration of mothers who had had children with rickets with those who had not (controls). Methods: We collected breast milk from 35 Nigerian mothers who had previously had children with nutritional rickets. For each case mother, we collected breast milk from three matched control mothers at the same stage of lactation (±4 weeks) who had had no children with rickets. Data were collected about parity, stage of lactation, and the infant's intake. The mother's bone density was measured. Results: The mean breast milk calcium concentration of mothers of children with rickets (4.30±1.24 mmol/L) was less than that of control mothers (4.65±1.03 mmol/L; P=0.034 in multivariate regression controlling for duration of lactation and resumption of menses). Forearm bone mineral content was significantly related to breast milk calcium concentration (r = 0.20) after adjusting for height, weight, and bone area (P=0.028). Conclusion: : Reduced breast‐milk calcium concentration may contribute to a reduced calcium intake in infancy and predispose children to nutritional rickets.

Case-control study of breast milk calcium in mothers of children with and without nutritional rickets

Despite similarly low calcium intakes and normal vitamin D status, only some Nigerian children develop nutritional rickets. We hypothesized that mothers with children who had developed rickets might have lower breast-milk calcium concentration than mothers with normal children and compared the breast-milk calcium concentration of mothers who had had children with rickets with those who had not (controls). We collected breast milk from 35 Nigerian mothers who had previously had children with nutritional rickets. For each case mother, we collected breast milk from three matched control mothers at the same stage of lactation (+/-4 weeks) who had had no children with rickets. Data were collected about parity, stage of lactation, and the infant's intake. The mother's bone density was measured. The mean breast milk calcium concentration of mothers of children with rickets (4.30+/-1.24 mmol/L) was less than that of control mothers (4.65+/-1.03 mmol/L; P=0.034 in multivariate regression controlling for duration of lactation and resumption of menses). Forearm bone mineral content was significantly related to breast milk calcium concentration (r=0.20) after adjusting for height, weight, and bone area (P=0.028). Reduced breast-milk calcium concentration may contribute to a reduced calcium intake in infancy and predispose children to nutritional rickets.

Serum 25-hydroxyvitamin D concentrations in girls aged 4–8 y living in the southeastern United States

Evidence suggests that adults and adolescents throughout the United States are at risk of poor vitamin D status. However, vitamin D concentrations in young American children have not been assessed. The relations between serum 25-hydroxyvitamin D [25(OH)D] and bone were examined in prepubertal girls. In the present cross-sectional study, serum 25(OH)D concentration was assessed in 168 prepubertal girls aged 4-8 y living in the southeastern United States with the use of radioimmunoassay. Bone area, bone mineral content, and areal bone mineral density were measured from total body, lumbar spine, proximal femur, and forearm with dual-energy X-ray absorptiometry. Data were analyzed with analysis of variance, analysis of covariance, stepwise multiple regression, and partial correlations. The mean (+/-SD) serum 25(OH)D was 93.8 +/- 28.1 nmol/L (range: 31.1-181.4 nmol/L). In a multiple regression analysis, race and season were the strongest predictors of vitamin D status. The black girls had lower mean 25(OH)D values than did the white girls (P < 0.01), and 25(OH)D values were significantly different in the total sample between the seasons (P < 0.001), ranging from 74.4 nmol/L during the winter months to 107 nmol/L during the summer. After adjustment for season, age, race, and body mass index, 25(OH)D values were negatively correlated with forearm bone mineral content (r = -0.18; P = 0.02). Unlike prior reports of adults and adolescents living in the southeastern United States, vitamin D status was adequate in the children of the present study. 25(OH)D concentrations were not positively associated with higher bone mineral.

A two‐year prospective controlled study of bone mass and bone turnover in children with early juvenile idiopathic arthritis

To explore early changes and predictors of bone mass in children with juvenile idiopathic arthritis (JIA) in order to identify patients who will develop bone mass reductions. We conducted a prospective cohort study of 108 children with early JIA (ages 6-18 years; mean disease duration 19.3 months) who were individually matched with 108 healthy children for age, sex, race, and county of residence. Bone mass and changes in total body, spine, femur, and forearm bone mineral density and bone mineral content (BMC), body composition, growth, and biochemical parameters of bone turnover were examined at baseline and at followup a mean of 24 months later. Low bone mass was defined as a Z score >1 SD below the reference population. Of the 200 children evaluated at followup, the 100 healthy children had greater gains in total body BMC (P = 0.035), distal radius BMC (P < 0.001), and total body lean mass (P < 0.001) than did the 100 JIA patients. Low or very low total body BMC was observed in 24% of the patients and 12% of the healthy children. Bone formation, bone resorption, and weight-bearing activities were reduced in the patients compared with the healthy children. Multiple regression analysis showed that in patients with JIA, serum bone-specific alkaline phosphatase, serum C-telopeptide of type I collagen, and weight-bearing activities were independent predictors of changes in total body BMC. Total body BMC was lower in patients with polyarticular onset than in those with oligoarticular disease onset. Patients with JIA have moderate reductions in bone mass gains, bone turnover, and total body lean mass early in the disease course.

Effects of Long-Term Tennis Playing on the Muscle-Bone Relationship in the Dominant and Nondominant Forearms

The relationship between muscle strength and bone mineral density illustrates the positive effect of mechanical loading on bone. But local and systemic factors may affect both muscle and bone tissues. This study investigated the effects of long-term tennis playing on the relationship between lean tissue mass and bone mineral content in the forearms, taking the body dimensions into account. Fifty-two tennis players (age 24.2 +/- 5.8 yrs, 16.2 +/- 6.1 yrs of practice) were recruited. Lean tissue mass (LTM), bone area, bone mineral content (BMC), and bone mineral density were measured at the forearms from a DXA whole-body scan. Grip strength was assessed with a dynamometer. A marked side-to-side difference (p < 0.0001) was found in favor of the dominant forearm in all parameters. Bone area and BMC correlated with grip strength on both sides (r = 0.81-0.84, p < 0.0001). The correlations were still significant after adjusting for whole-body BMC, body height, or forearm length. This result reinforced the putative role of the muscles in the mechanical loading on bones. In addition, forearm BMC adjusted to LTM or grip strength was higher on the dominant side, suggesting that tennis playing exerts a direct effect on bone.