Different indices of fetal growth predict bone size and volumetric density at 4 years of age

We have demonstrated previously that higher birth weight is associated with greater peak and later‐life bone mineral content and that maternal body build, diet, and lifestyle influence prenatal bone mineral accrual. To examine prenatal influences on bone health further, we related ultrasound measures of fetal growth to childhood bone size and density. We derived Z‐scores for fetal femur length and abdominal circumference and conditional growth velocity from 19 to 34 weeks' gestation from ultrasound measurements in participants in the Southampton Women's Survey. A total of 380 of the offspring underwent dual‐energy X‐ray absorptiometry (DXA) at age 4 years [whole body minus head bone area (BA), bone mineral content (BMC), areal bone mineral density (aBMD), and estimated volumetric BMD (vBMD)]. Volumetric bone mineral density was estimated using BMC adjusted for BA, height, and weight. A higher velocity of 19‐ to 34‐week fetal femur growth was strongly associated with greater childhood skeletal size (BA: r = 0.30, p < .0001) but not with volumetric density (vBMD: r = 0.03, p = .51). Conversely, a higher velocity of 19‐ to 34‐week fetal abdominal growth was associated with greater childhood volumetric density (vBMD: r = 0.15, p = .004) but not with skeletal size (BA: r = 0.06, p = .21). Both fetal measurements were positively associated with BMC and aBMD, indices influenced by both size and density. The velocity of fetal femur length growth from 19 to 34 weeks' gestation predicted childhood skeletal size at age 4 years, whereas the velocity of abdominal growth (a measure of liver volume and adiposity) predicted volumetric density. These results suggest a discordance between influences on skeletal size and volumetric density. © 2010 American Society for Bone and Mineral Research     

Longitudinal Trends in Use of Bone Mass Measurement Among Older Americans, 1999–2005

Bone mass measurement (BMM) is useful to identify persons with low bone mass who are at increased risk for fracture. Given the increased emphasis that is being placed on preventive services such as screening for osteoporosis, we evaluated trends in BMM among Medicare beneficiaries. We studied a 5% sample of Medicare beneficiaries ≥65 yr of age in 1999–2005. We identified claims for BMM tests performed in both facility and nonfacility settings, evaluated temporal trends in use of these tests, and described the proportion of tests attributable to each specialty of physicians submitting claims. We also assessed patterns of serial testing among individuals who were tested more than once. Claims data from all years were pooled to describe the proportion of persons in the population ever tested. From 1999 to 2005, use of central DXA increased by ～50%, and use of peripheral DXA declined. The greatest increases in central DXA occurred among internists, family practitioners, and gynecologists. In 1999, the proportion of 65‐yr‐old women tested was 8.4%; this increased to 12.9% in 2005. Corresponding proportions for men were 0.6% and 1.7%, respectively. Between 40% and 73% of persons receiving central DXA were retested, most at ～2‐yr intervals. Aggregating data across all years for whites and blacks, 30.0% of women and 4.4% of men underwent central DXA at least once. We conclude that, although use of DXA steadily increased from 1999 to 2005, only ～30% of women and 4% of men at least 65 yr old had a central DXA study. Given the importance of central DXA to assess the risk of osteoporotic fractures, strategies to increase central DXA use to test at‐risk persons are warranted.     

Maternal Height, Childhood Growth and Risk of Hip Fracture in Later Life: A Longitudinal Study

Although measures to enhance bone mineralization during childhood and adolescence are widely incorporated into preventive programmes against osteoporotic fracture, there are no published data directly linking growth rates in childhood with the risk of later hip fracture. We addressed this issue in a unique Finnish cohort in whom birth and childhood growth data were linked to later hospital discharge records. This permitted follow-up of 3639 men and 3447 women who were born in Helsinki University Central Hospital between 1924 and 1933, who went to school in Helsinki and still lived in Finland in 1971. Body size at birth was recorded and an average of 10 measurements were obtained of height and weight throughout childhood. We identified 112 subjects (55 men and 57 women) who sustained a hip fracture during 165 404 person-years of follow-up. After adjustment for age and sex in a proportional hazards model, we identified two major determinants of hip fracture risk: tall maternal height (p<0.001) and a low rate of childhood growth (height, p= 0.006; weight, p = 0.01). The hazard ratio for hip fracture was 2.1 (95% CI 1.2–3.5) among men and women born to mothers taller than 1.61 m, when compared with those whose mothers were shorter than 1.54 m. The ratio was 1.9 (95% CI 1.1–3.2) among those whose rate of childhood height gain was below the lowest quartile for the cohort, compared with those whose growth rate was above the highest quartile. The effects of maternal height and childhood growth rate were statistically independent of each other, and remained after adjusting for socioeconomic status. The patterns of childhood growth that predicted future hip fracture differed between boys and girls. In boys, there was a constant deficit in height and weight between ages 7 and 15 years among those later sustaining fractures; in girls, there was a progressively increasing deficit in weight but a delayed height gain among those later sustaining fractures. This epidemiologic study provides the first direct evidence that a low rate of childhood growth is a risk factor for later hip fracture. Whether reduced growth rate is a consequence of childhood lifestyle, genetic background or intrauterine hormonal programming, the data support measures to optimize childhood growth as part of preventive strategies against osteoporotic fracture in future generations. Received: May 2000 / Accepted: June 2001     

Maternal Vitamin D Status During Pregnancy and Bone Mass in Offspring at 20 Years of Age: A Prospective Cohort Study

It is uncertain whether the vitamin D status of pregnant women influences bone mass of their children. Cohort studies have yielded conflicting results; none have examined offspring at skeletal maturity. This longitudinal, prospective study investigated the association between maternal vitamin D status and peak bone mass of offspring in 341 mother and offspring pairs in the Western Australian Pregnancy Cohort (Raine) Study. Maternal serum samples collected at 18 weeks gestation were assayed for 25‐hydroxyvitamin D (25OHD). Outcomes were total body bone mineral content (BMC) and bone mineral density (BMD) measured by dual‐energy X‐ray absorptiometry in offspring at 20 years of age. The mean (± SD) maternal serum 25OHD concentration was 57.2 ± 19.2 nmol/L; 132 women (38.7%) were vitamin D‐deficient (25OHD <50 nmol/L). After adjustment for season of sample collection, maternal factors, and offspring factors (sex, birth weight, and age, height, lean mass, and fat mass at 20 years), maternal 25OHD concentration was positively associated with total body BMC and BMD in offspring, with a mean difference of 19.2 (95% confidence interval [CI], 5.6–32.7) g for BMC and 4.6 (95% CI, 0.1–9.1) mg/cm² for BMD per 10.0 nmol/L of maternal 25OHD. Maternal vitamin D deficiency was associated with 2.7% lower total body BMC (mean ± SE) (2846 ± 20 versus 2924 ± 16 g, p = 0.004) and 1.7% lower total body BMD (1053 ± 7 versus 1071 ± 5 mg/cm², p = 0.043) in the offspring. We conclude that vitamin D deficiency in pregnant women is associated with lower peak bone mass in their children. This may increase fracture risk in the offspring in later life. © 2014 American Society for Bone and Mineral Research.     

Calcium and Bone Metabolism During Pregnancy and Lactation

Pregnancy and lactation both place significant demands on the mother to provide sufficient calcium (among other minerals and nutrients) to the fetus and neonate. Despite facing similar demands for calcium during pregnancy and lactation, the maternal adaptations differ significantly between these two reproductive periods. Women lose 300 to 400 mg of calcium daily through breast milk, and this calcium demand is met by a 5–10% loss of skeletal mineral content during 6 months of exclusive lactation. Most importantly, the lost mineral is fully restored within a few months of weaning, such that women who have breastfed do not have a long-term deficit in skeletal mineral content. This article will review our present understanding of the adaptations in mineral metabolism that occur during pregnancy and lactation, and will focus on recent evidence that the breast itself plays a central role in regulating the adaptations during lactation.     

Pamidronate Administration During Pregnancy and Lactation Induces Temporal Preservation of Maternal Bone Mass in a Mouse Model of Osteogenesis Imperfecta

During pregnancy and lactation, the maternal skeleton undergoes significant bone loss through increased resorption to provide the necessary calcium supply to the developing fetus and suckling neonate. This period of skeletal vulnerability has not been clearly associated with increased maternal fracture risk, but these physiological conditions can exacerbate an underlying metabolic bone condition like osteogenesis imperfecta. Although bisphosphonates (BPs) are commonly used in postmenopausal women, there are cases where premenopausal women taking BPs become pregnant. Given BPs’ long half-life, there is a need to establish how BPs affect the maternal skeleton during periods of demanding metabolic bone changes that are critical for the skeletal development of their offspring. In the present study, pamidronate- (PAM-) amplified pregnancy-induced bone mass gains and lactation-induced bone loss were prevented. This preservation of bone mass was less robust when PAM was administered at late stages of lactation compared with early pregnancy and first day of lactation. Pregnancy-induced osteocyte osteolysis was also observed and was unaffected with PAM treatment. No negative skeletal effects were observed in offspring from PAM-treated dams despite lactation-induced bone loss prevention. These findings provide important insight into (1) a treatment window for when PAM is most effective in preserving maternal bone mass, and (2) the maternal changes in bone metabolism that maintain calcium homeostasis crucial for fetal and neonatal bone development. © 2019 American Society for Bone and Mineral Research     

Breastfeeding in Early Life and Bone Mass in Prepubertal Children: A Longitudinal Study

The aim of this study was to determine whether breastfeeding in early life is associated with bone mass in prepubertal children. We studied 330 8-year-old male and female children from Southern Tasmania representing 47% of those who originally took part in a birth cohort study of risk factors for Sudden Infant Death Syndrome in 1988. Breastfeeding intention and habit were assessed in both 1988 and 1996. Bone mineral density was measured by dual-energy X-ray densitometry. Children who were breastfed had higher bone mineral density at the femoral neck (+0.20 SD, p= 0.07), lumbar spine (+0.25 SD, p= 0.03) and total body (+0.29 SD, p= 0.006) compared with those who were bottle-fed. This association with breastfeeding was present in children born at term (femoral neck: +0.26 SD, p= 0.05; lumbar spine: +0.34 SD, p= 0.007; total body: +0.41 SD, p= 0.0008) but not those born preterm, and remained significant after adjustment for size, lifestyle factors and socioeconomic factors. Breastfeeding for less than 3 months was not associated with increased bone mass at any site. In conclusion, this study has demonstrated a beneficial association between breastfeeding in early life and bone mass in 8-year-old children born at term, particularly those breastfed for 3 months or longer, which appears biological. If this association is confirmed in other populations and persists until the attainment of peak bone mass then the implication would be that osteoporosis prevention programs need to start very early in the life cycle. Received: 18 December 1998 / Accepted: 7 July 1999     

Osteonecrosis and Spontaneous Fractures Following Renal Transplantation: A Longitudinal Study of Radiological Bone Changes and Metacarpal Bone Mass

Seventy-seven renal transplant (RT) recipients were studied radiologically with regard to bone lesions and metacarpal bone mass, at the time of and after renal transplantation. An increased incidence of rarefaction of the spine, a reduced metacarpal bone mass and an increased frequency of subperiosteal erosions were found at the time of transplantation in RT patients who subsequently developed osteonecrosis or spontaneous fractures as compared with RT patients who did not develop these bone complications. During the years after RT an increase in rarefaction of the spine, in subperiosteal erosions, in soft tissue calcifications and a decrease in metacarpal bone mass were found in all patient groups.     

Fetal and Childhood Growth Patterns Associated with Bone Mass in School‐Age Children: The Generation R Study

Low birth weight is associated with lower bone accrual in children and peak bone mass in adults. We assessed how different patterns of longitudinal fetal and early childhood growth influence bone properties at school age. In 5431 children participating in a population‐based prospective cohort study, we measured fetal growth by ultrasound at 20 and 30 weeks gestation, and childhood growth at birth, 1, 2, 3, and 4 years of age. We analyzed these growth measurements in relation to total body (less head) BMD measured by DXA at age 6. We used conditional growth modeling; a technique which takes into account correlation between repeatedly measured growth measures. Our results showed that estimated fetal weight gain, femur length growth between 20 and 30 weeks of gestation, femur length growth between 30 weeks and birth, as well as all height and weight growth measurements from birth to 4 years of age were all positively associated with BMC, bone area (BA), and BMD (all p < 0.01). Fetal femur length growth between 30 weeks and birth was positively associated with BMC and BA (both p < 0.001), but not with BMD. Overall, childhood growth measurements exerted a larger influence on bone measures than fetal growth measures. The strongest effect estimate was observed during the first year of life. Children born small (<10th percentile) for gestational age (SGA) had lower BMC and BA, but not BMD, than children born appropriate for gestational age (AGA), whereas children born large (>90th percentile) for gestational age (LGA) had higher BMC and BA (all p < 0.001). These differences were no longer present in children showing subsequent accelerated and decelerated infant growth, respectively. We conclude that both fetal and childhood growth patterns are associated with bone mineral accrual, showing the strongest effect estimates in infancy . Compensatory infant growth counteracts the adverse consequences of fetal growth restriction on bone development. © 2014 American Society for Bone and Mineral Research.     

Low maternal vitamin D status and fetal bone development: Cohort study

Recent findings suggest that maternal vitamin D insufficiency during pregnancy has consequences for the offspring's bone health in later life. To investigate whether maternal vitamin D insufficiency affects fetal femur growth in ways similar to those seen in childhood rickets and study the timing during gestation of any effect of maternal vitamin D status, we studied 424 pregnant women within a prospective longitudinal study of maternal nutrition and lifestyle before and during pregnancy (Southampton Women's Survey). Using high‐resolution 3D ultrasound, we measured fetal femur length and distal metaphyseal cross‐sectional area, together with the ratio of femoral metaphyseal cross‐sectional area to femur length (femoral splaying index). Lower maternal 25‐hydroxyvitamin vitamin D concentration was not related to fetal femur length but was associated with greater femoral metaphyseal cross‐sectional area and a higher femoral splaying index at 19 weeks' gestation [r = ?0.16, 95% confidence interbal (CI) ?0.25 to ?0.06 and r = ?0.17, 95% CI ?0.26 to ?0.07, respectively] and at 34 weeks' gestation (r = –0.10, 95% CI ?0.20 to 0.00 and r = ?0.11, 95% CI ?0.21 to ?0.01, respectively). Three groups of women were identified with 25‐hydroxyvitamin vitamin D concentrations that were sufficient/borderline (>50 nmol/L, 63.4%), insufficient (25 to 50 nmol/L, 30.7%), and deficient (≤25 nmol/L, 5.9%). Across these groups, the geometric mean femoral splaying indices at 19 weeks' gestation increased from 0.074 (sufficient/borderline) to 0.078 (insufficient) and 0.084 (deficient). Our observations suggest that maternal vitamin D insufficiency can influence fetal femoral development as early as 19 weeks' gestation. This suggests that measures to improve maternal vitamin D status should be instituted in early pregnancy. © 2010 American Society for Bone and Mineral Research     

A Histomorphometric Long-Term Longitudinal Study of Trabecular Bone Loss in Glucocorticoid-Treated Patients: Prednisone Versus Deflazacort

Administration of a corticosteroid with minor osteopenic effects is considered an effective prevention of glucocorticoid osteoporosis. Deflazacort, an oxazolinic derivative of prednisolone, is reported to be less harmful to cancellous bone mass than other equally effective corticosteroids. However, comparative long-term studies, particularly on trabecular bone, are needed before a smaller detrimental effect on bone of deflazacort can be unequivocally confirmed. We conducted such a prospective long-term study using histomorphometric analysis of iliac bone. For the study, 18 pairs of nonimmobilized patients, matched for age, sex, menopausal state, corticosteroid dose, and type and severity of the disease, were randomly submitted to treatment with therapeutically equivalent doses of prednisone or deflazacort. Bone biopsies from iliac crest were taken before and at various times during treatment. In order to represent the time-related trabecular bone loss and find out possible differences between patients on prednisone or deflazacort, a previously described model of bone loss kinetics was applied. No significant differences in biochemical indices of bone turnover or in histomorphometric variables between prednisone- and deflazacort-treated patients were recorded before treatment. The mean duration of treatment at the final biopsy was similar for prednisone and deflazacort (15.8 and 15.2 months, respectively). Patients showed evident clinical improvement with both treatments. Osteoid and resorption surfaces showed no significant differences throughout the observation period in any of the 18 pairs. On the contrary, both steroids induced a significant decrease in trabecular bone, although the bone loss rate induced by prednisone was significantly higher than that induced by deflazacort (P < 0.05). The kinetics of bone loss and the different osteopenic effects of the two drugs are described by the negative exponential function fitted to data from patients never previously given glucocorticoids; the model yields highly significant difference (P≅ 0.01) between the two drugs and allows estimation of the difference even 3 years after the beginning of treatment (−3.0%/year versus −1.1%/year for prednisone and deflazacort, respectively). This prospective long-term study confirms that an exponential model accurately describes the trabecular bone loss induced by long-term corticosteroid treatment and demonstrates that deflazacort, at therapeutically effective doses, induces less trabecular bone loss than prednisone. Received: 30 January 1997 / Accepted: 7 August 1997     

Bone and Muscle Development During Puberty in Girls: A Seven‐Year Longitudinal Study

The growth of lean mass precedes that of bone mass, suggesting that muscle plays an important role in the growth of bone. However, to date, no study has directly followed the growth of bone and muscle size through puberty and into adulthood. This study aimed to test the hypothesis that the growth of muscle size precedes that of bone size (width and length) and mass during puberty. Bone and muscle properties were measured using pQCT and DXA in 258 healthy girls at baseline (mean age, 11.2 yr) and 1‐, 2‐, 3–4‐ and 7‐yr follow‐up. Growth trends as a function of time relative to menarche were determined from prepuberty to early adulthood for tibial length (TL), total cross‐sectional area (tCSA), cortical CSA (cCSA), total BMC (tBMC), cortical volumetric BMD (cBMD), and muscle CSA (mCSA) in hierarchical models. The timings of the peak growth velocities for these variables were calculated. Seventy premenopausal adults, comprising a subset of the girl's mothers (mean age, 41.5 yr), were included for comparative purposes. In contrast to our hypothesis, the growth velocity of mCSA peaked 1 yr later than that of tibial outer dimensions (TL and tCSA) and slightly earlier than tBMC. Whereas TL ceased to increase 2 yr after menarche, tCSA, cCSA, tBMC, and mCSA continued to increase and were still significantly lower than adult values at the age of 18 yr (all p < 0.01). The results do not support the view that muscle force drives the growth of bone size during puberty.     

Longitudinal Trajectories of Television Watching Across Childhood and Adolescence Predict Bone Mass at Age 20 Years in the Raine Study

Sedentary behaviors such as watching television (TV) are associated with increased risk of cardiometabolic disease. The effects of TV watching during key developmental stages on skeletal health are uncertain. Hours of TV watching/week were recorded by parental or self‐report at 5, 8, 10, 14, 17, and 20 years of age in 1181 members (48% female) of a pregnancy cohort (the Raine Study). Participants were classified into one of three TV‐watching trajectories (using latent class analysis): low (consistently <14 h/week; 20.3%), high (consistently ≥14 h/week; 44.4%), or increasing (increased from <14 to ≥14 h/week during adolescence; 35.3%). General linear models tested associations between TV trajectory and bone mineral content (BMC) measured at age 20 years using dual‐energy X‐ray absorptiometry. After adjustment for height, body mass, physical activity, calcium intake, serum 25‐hydroxyvitamin D levels, alcohol, and smoking (all at age 20 years), males in the low TV‐watching trajectory had greater BMC for whole body (mean ± SEM, 3338 ± 59 g versus 3111 ± 31 g), legs (612 ± 12 g versus 569 ± 6 g), and arms (234 ± 5 g versus 214 ± 3 g) than those in the high TV‐watching trajectory. Differences between low and high TV‐watching trajectories were similar for females. BMC in the increasing TV‐watching trajectory also differed for both sexes, for example males in the increasing TV‐watching trajectory had greater whole‐body BMC (3252 ± 38 g) than males in the high TV‐watching trajectory (3111 ± 31 g) but less arm BMC (218 ± 3 g) than those in the low TV‐watching trajectory (234 ± 5 g). In this community‐based cohort, consistently high TV watching during childhood and adolescence independently predicted reduced peak bone mass at age 20 years. Because attainment of optimal peak bone mass is protective against osteoporosis in later life, reducing sedentary time in children may have long‐term skeletal benefits. © 2016 American Society for Bone and Mineral Research.     

Continuous Loss of Bone During Chronic Immobilization: A Monozygotic Twin Study

Acute immobilization is associated with rapid loss of bone. Prevailing opinion, based on population cross-sectional data, assumes that bone mass stabilizes thereafter. In order to address whole-body and regional skeletal mass in long-term immobilization, monozygotic twins were studied, one of each twin pair having chronic spinal cord injury (SCI) of a duration ranging from 3 to 26 years. The research design consisted of the co-twin control method using 8 pairs of identical male twins (mean ± SD age, 40 ± 10 years; range 25–58 years), one of each set with SCI. The twins were compared by paired t-tests for total and regional bone mineral content (BMC) and bone mineral density (BMD) measured by dual-energy X-ray absorptiometry. Linear regression analyses were performed to determine the associations of age or duration of injury with the differences between twin pairs for total and regional skeletal bone values. In the SCI twins, total-body BMC was significantly reduced (22%± 9%, p<0.001), with the predominant sites of reduction for BMC and BMD being the legs (42%± 14% 35%± 10%, p<0.0001), and pelvis (50%± 10% and 29%± 9%, p<0.0001). Duration of SCI, not age, was found to be linearly related to the degree of leg bone loss in SCI twins (BMC: r ²= 0.60, p<0.05; BMD: r ²= 0.70, p<0.01). Our findings suggest that pelvic and leg bone mass continues to decline throughout the chronic phase of immobilization in the individual with SCI, and this bone loss appears to be independent of age. Received: 28 September 1998 / Accepted: 28 December 1998     

Associations Between Late Pregnancy Dietary Inflammatory Index (DII) and Offspring Bone Mass: A Meta-Analysis of the Southampton Women's Survey (SWS) and the Avon Longitudinal Study of Parents and Children (ALSPAC)

Systemic inflammation is associated with reduced bone mineral density and may be influenced by pro-inflammatory diets. We undertook an observational analysis of associations between late pregnancy energy-adjusted dietary inflammatory index (E-DII) scores and offspring bone outcomes in childhood. E-DII scores (higher scores indicating pro-inflammatory diets) were derived from food frequency questionnaires in late pregnancy in two prospective mother-offspring cohorts: the Southampton Women's Survey (SWS) and the Avon Longitudinal Study of Parents and Children (ALSPAC). The mean (SD) offspring age at dual-energy X-ray absorptiometry (DXA) scanning was 9.2 (0.2) years. Linear regression was used to assess associations between E-DII and bone outcomes, adjusting for offspring sex and age at DXA and maternal age at childbirth, educational level, pre-pregnancy body mass index (BMI), parity, physical activity level, and smoking in pregnancy. Associations were synthesized using fixed-effect meta-analysis. Beta coefficients represent the association per unit E-DII increment. In fully adjusted models (total n = 5910) late pregnancy E-DII was negatively associated with offspring whole body minus head bone area (BA: β = −3.68 [95% confidence interval −6.09, −1.27] cm²/unit), bone mineral content (BMC: β = −4.16 [95% CI −6.70, −1.62] g/unit), and areal bone mineral density (aBMD: β = −0.0012 [95% CI −0.0020, −0.0004] g.cm⁻²/unit), but there was only a weak association with BMC adjusted for BA (β = −0.48 [95% CI −1.11, 0.15] g/unit) at 9 years. Adjustment for child height partly or, for weight, fully attenuated the associations. Higher late pregnancy E-DII scores (representing a more pro-inflammatory diet) are negatively associated with offspring bone measures, supporting the importance of maternal and childhood diet on longitudinal offspring bone health. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).     

Growth and Bone Mineral Accretion During Puberty in Chinese Girls: A Five‐Year Longitudinal Study

There are few longitudinal data on bone development during puberty in children with low calcium intake. This 5‐yr longitudinal study showed that, in Chinese girls, the mean apparent calcium retention efficiency during puberty was 40.9%, PHV occurred at 3–0 yr before menarche, and peak bone mineral accretion occurred 1 yr later than PHV. Chinese girls have high calcium retention efficiency during puberty. Introduction: There are few longitudinal data on bone development during puberty in children with low dietary calcium intake. The aim of this study was to examine the rate of growth and bone mineral accretion and study the predictors of total body BMC during puberty in a 5‐yr longitudinal study with Chinese girls. Materials and Methods: Ninety‐two girls, 9.5–10.5 yr of age at baseline, from the unsupplemented control group of a school milk intervention trial were included in this analysis. Data on anthropometric measurements, total body BMC as assessed by DXA, and calcium intake as assessed by a 3‐day food record were obtained at baseline and 1, 2, 4, and 5 yr. Results: The mean age of menarche was 12.1 ± 1.0 yr. The mean annual rate of bone mineral accretion was 197.4 g/yr during the follow‐up period, representing a calcium accretion rate of 162.3 mg/d. This calcium retention rate and the average dietary calcium intake of 444.1 mg/d gave an apparent calcium retention efficiency of 40.9%. Peak height velocity (PHV) occurred at 3–0 yr before menarche. Peak bone mineral accretion occurred 1 yr later than PHV. There was a decrease in size‐corrected BMD in the year before menarche. In the linear mixed‐effects model analysis containing body size and lifestyle factors, we found that height, body weight, and calcium intake were significant independent predictors of total body BMC. Conclusions: Chinese girls with low habitual dietary calcium intake have high calcium retention efficiency during puberty. Because calcium intake is a significant predictor of total body BMC, increasing dietary calcium intake may have beneficial effects on bone mineral accretion in these girls.     

Longitudinal Changes in BMD and Bone Geometry in a Population‐Based Study

We prospectively examined vBMD and structural bone parameters assessed by QCT among participants of the InCHIANTI study over a 6‐yr follow‐up. Periosteal apposition occurred both in men and women. Endocortical resorption causes bone loss in older women despite periosteal apposition. Introduction: To address the hypothesis that age‐related changes in BMD and bone geometry may be different in men and women, we prospectively examined volumetric BMD (vBMD) and structural bone parameters assessed by QCT among participants of the InCHIANTI study over a 6‐yr follow‐up. Materials and Methods: Three hundred forty‐five men and 464 women 21–102 yr of age from the InCHIANTI study, a population‐based study in Tuscany, Italy, were included. Tibial QCT bone parameters were measured at enrollment (1998–2000) and at 3‐ (2001–2003) and 6‐yr (2004–2006) follow‐ups. Results: Periosteal apposition occurred both in men and women. The annual rate of bone periosteal apposition was higher in younger than in older men, whereas in women, the rate of apposition was homogenous across age groups. The age‐related medullary expansion, expression of endocortical resorption, was significantly higher in women compared with men. In women, but not in men, accelerated endocortical resorption not sufficiently balanced by periosteal apposition caused accelerated loss in cortical bone mass. The cross‐sectional moment of inertia decreased progressively over the life span in both sexes. Conclusions: Endocortical resorption causes bone loss in older women despite periosteal apposition. Obtaining a balance between endocortical resorption and periosteal apposition should be the target for interventions aimed to decrease bone loss and prevent osteoporosis in older women.     

The Longitudinal Effects of Physical Activity and Dietary Calcium on Bone Mass Accrual Across Stages of Pubertal Development

Childhood and adolescence are critical periods of bone mineral content (BMC) accrual that may have long‐term consequences for osteoporosis in adulthood. Adequate dietary calcium intake and weight‐bearing physical activity are important for maximizing BMC accrual. However, the relative effects of physical activity and dietary calcium on BMC accrual throughout the continuum of pubertal development in childhood remains unclear. The purpose of this study was to determine the effects of self‐reported dietary calcium intake and weight‐bearing physical activity on bone mass accrual across the five stages of pubertal development in a large, diverse cohort of US children and adolescents. The Bone Mineral Density in Childhood study was a mixed longitudinal study with 7393 observations on 1743 subjects. Annually, we measured BMC by dual‐energy X‐ray absorptiometry (DXA), physical activity and calcium intake by questionnaire, and pubertal development (Tanner stage) by examination for up to 7 years. Mixed‐effects regression models were used to assess physical activity and calcium intake effects on BMC accrual at each Tanner stage. We found that self‐reported weight‐bearing physical activity contributed to significantly greater BMC accrual in both sexes and racial subgroups (black and nonblack). In nonblack males, the magnitude of the activity effect on total body BMC accrual varied among Tanner stages after adjustment for calcium intake; the greatest difference between high‐ and low‐activity boys was in Tanner stage 3. Calcium intake had a significant effect on bone accrual only in nonblack girls. This effect was not significantly different among Tanner stages. Our findings do not support differential effects of physical activity or calcium intake on bone mass accrual according to maturational stage. The study demonstrated significant longitudinal effects of weight‐bearing physical activity on bone mass accrual through all stages of pubertal development. © 2014 American Society for Bone and Mineral Research.     

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

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