Adult Bone Mineral Content Research Articles

Chloroform associated with bone mineral density and bone mineral content in adults: A population-based cross-sectional research.

Bone mineral density is an important indicator of osteoporosis, and its variation with volatile organic compounds exposure has rarely been studied. However, the relationship between chloroform (an essential volatile organic compounds component) and bone mineral density remains unclear. Consequently, we aimed to explore the relationship between chloroform alone and bone mineral density or bone mineral content. Herein, 2,553 individuals aged 18 and above from the National Health and Nutrition Examination Surveys (NHANES) in 2009-2010, 2013-2014, and 2017-2020, were included. We employed two independent t-tests and multi-linear regression models to statistically assess the relationship between chloroform exposure and BMD/BMC in the spine and femoral area. A "V"-shaped correlation between chloroform exposure and bone mineral density or bone mineral content (BMD/BMC) was observed in the unadjusted model, particularly in the Ward's triangle and femoral neck as a whole. A negative correlation was specifically observed for the Ward's triangle BMD/BMC and L4 BMD/BMC. On the other hand, in the adjusted model, a dominantly negative correlation between the L4 BMC and chloroform exposure was observed over a range of exposure levels. The subgroup analysis revealed a negative correlation between chloroform concentrations and BMC in the femur and spine, especially in women and the 65-80 age population. Our study revealed a "V" shaped correlation between chloroform and BMD/BMC of the femur and spine in U.S. adults. This finding highlights the fact that prolonged exposure to chloroform may cause the changes in BMD/BMC.

Relationship between blood manganese and bone mineral density and bone mineral content in adults: A population-based cross-sectional study.

PurposeIt has been reported that bone is the primary organ for manganese (Mn) accumulation, but the association between manganese and bone loss remains debatable. Therefore, this study aimed to evaluate the relationship between blood manganese and bone mineral density/bone mineral content (BMD/BMC) by using a representative sample from the National Health and Nutrition Examination Survey (NHANES).MethodsA total of 9732 subjects over the age of 18 with available data were enrolled in this study. The relationship between blood manganese and BMD/BMC of the total body, spine and femoral regions was evaluated using multivariate linear regression models. Subgroup analyses were also performed.ResultsWe observed a negative association between blood manganese and BMD/BMC in the femoral neck and total body in the fully adjusted model, especially femoral neck BMD in women aged 50–70 years.ConclusionIn brief, people exposed to manganese should be aware of the increased risk of osteopenia or osteoporosis. Besides, due to the lack of available data, there are no definite values for the tolerable upper intake level (UL), average requirement (AR) and population reference intake (PRI) of manganese. The results of our study may provide some references for the establishment of AR, PRI and UL of Mn.

Bone mineral density in very low birthweight adults-A sibling study.

BackgroundChildren and adults born very low birthweight (VLBW, <1500 g) at preterm gestations have lower bone mineral density (BMD) and/or bone mineral content (BMC) than those born at term, but causality remains unknown.ObjectivesOur aim was to assess BMD and BMC in adults born at VLBW in a sibling comparison setting to account for shared genetic and environmental confounders.MethodsWe conducted a cohort study of 77 adults born VLBW and 70 same‐sex term‐born siblings at mean age of 29 years. The primary outcome variables were BMD Z‐scores, and BMC, of the femoral neck, lumbar spine, and whole body, measured using dual‐energy X‐ray absorptiometry. We analysed data by linear mixed models.ResultsThe VLBW adults had a 0.25 (95% CI 0.02, 0.47) Z‐score unit lower femoral neck BMD, and 0.35 (95% CI 0.16, 0.54) grams lower femoral neck BMC than their term‐born siblings, after adjustment for sex, age, and maternal smoking. Additional adjustment for adult body size attenuated the results. Lumbar spine, and whole body BMC were also lower in the VLBW group.ConclusionsIndividuals born at VLBW had lower BMC values at all three measurement sites, as well as lower femoral neck BMD Z‐scores, compared to term‐born siblings, partly explained by their smaller adult body size, but the differences were smaller than those reported previously with unrelated controls. This suggests that genetic or environmental confounders explain partly, but not exclusively, the association between preterm VLBW birth and adult bone mineralisation.

Bone material properties and response to teriparatide in osteoporosis due to WNT1 and PLS3 mutations.

Patients with osteoporosis-associated WNT1 or PLS3 mutations have unique bone histomorphometric features and osteocyte-specific hormone expression patterns. To investigate the effects of WNT1 and PLS3 mutations on bone material properties. Transiliac bone biopsies were evaluated by quantitative backscattered electron imaging, immunohistochemistry, and bone histomorphometry. Ambulatory patients. Three pediatric and eight adult patients with WNT1 or PLS3 mutations. Bone mineralization density distribution and osteocyte protein expression was evaluated in 11 patients and repeated in six patients who underwent repeat biopsy after 24months of teriparatide treatment. Bone mineralization density distribution and protein expression. Children with WNT1 or PLS3 mutations had heterogeneous bone matrix mineralization, consistent with bone modeling during growth. Bone matrix mineralization was homogenous in adults and increased throughout the age spectrum. Teriparatide had very little effect on matrix mineralization or bone formation in patients with WNT1 or PLS3 mutations. However, teriparatide decreased trabecular osteocyte lacunae size and increased trabecular bone FGF23 expression. The contrast between preserved bone formation with heterogeneous mineralization in children and low bone turnover with homogenous bone mineral content in adults suggests that WNT1 and PLS3 have differential effects on bone modeling and remodeling. The lack of change in matrix mineralization in response to teriparatide, despite clear changes in osteocyte lacunae size and protein expression, suggests that altered WNT1 and PLS3 expression may interfere with coupling of osteocyte, osteoblast, and osteoclast function. Further studies are warranted to determine the mechanism of these changes.

Factors associated with bone mineral content in adults: a population-based study.

ABSTRACTObjective To determine the association among bone mineral content, sociodemographic, anthropometric and behavioral factors, and health status of Brazilian adults.Methods This was a cross-sectional, population-based study including 701 individuals from both sexes aged between 20 and 59 years. DEXA was used to evaluate dependent variable. The associations were evaluated using linear regression models stratified by sex.Results When mean bone mineral content values were compared, we found significant differences related to sex and all the independent variables evaluated. In the adjusted models, we identified an inverse association between bone mineral content and age in both sexes. Among men, to be overweight and/or obese, be highly educated, and have almost sufficiency of 25(OH)D were associated with higher bone mineral content values. On the other hand, among women, to be non-white skin color, overweight and/or obese were associated with better bone health. The main factors associated with low total bone mineral density were advanced age, white skin color, low level of formal education, eutrophy, and 25(OH)D deficiency.Conclusion Our results may help to identify adults who are at higher risk, and these findings should be used as guidelines for prevention and early diagnosis.

Long-term childhood body mass index and adult bone mass are linked through concurrent body mass index and body composition.

Body mass plays a crucial role in the bone growth and development, but few studies have examined the association of long-term cumulative impact and trajectory patterns of childhood body mass index (BMI) with adult bone mass, and the mediation effect of adult BMI and body composition on these associations. A total of 397 Chinese adults (54.4%) who had been examined for BMI 4-8 times during childhood (6-19 years) and bone mass in adulthood (29-37 years), were included for analysis. Adult bone mineral content (BMC), areal bone mineral density (aBMD) and body composition were assessed via dual-energy x-ray absorptiometry. Childhood BMI growth curves were constructed using a random-effects mixed model. The area under the curve (AUC) was calculated to represent the long-term impact of childhood BMI. At baseline, 24.4%, 66.2%, 7.6% and 1.8% of the participants were underweight, normal weight, overweight and obese, respectively. Quadratic curve parameters of childhood BMI differed significantly between groups of adult whole body (WB) BMC, lumbar spine (LS) aBMD and femoral neck (FN) aBMD, with low BMC/aBMD groups having lower childhood BMI than the normal groups. AUC of childhood BMI was significantly and positively related to adult WB BMC and aBMD at each site, irrespective of sex. Significant mediation effects of adult BMI were shown on the association of childhood BMI AUC with adult WB BMC in males (52.0%) and FN aBMD in both sexes (males: 65.4%; females: 64.3%). Additionally, mediation effect of fat mass index was only noted on the association of childhood BMI AUC with adult WB BMC (41.3%), with a positive total indirect effect estimated at 0.118. The adult lean mass index, by contrast, mediated the childhood BMI-adult BMC/aBMD association positively at all sites in males (71.5%~89.2%) and at WB BMC in females (45.0%). These findings suggest that the impact of body weight on adult bones originates from childhood, which is mediated by concurrent BMI and body composition.

Assessment of bone mineral content and fracture risk: a UK prospective cohort study

BackgroundPoor early growth is associated with reduced adult bone mineral content (BMC), but not bone mineral density (BMD). Although low BMD is a well-established risk factor for future fracture, little is known about the performance characteristics of BMC in fracture prediction. We therefore investigated the predictive value of bone area, BMC, and BMD for incident fracture in a prospective cohort of UK women. MethodsWomen aged 20–80 years, recruited from four general practices in Southampton, underwent assessment by dual energy X-ray absorptiometry between 1991 and 1993. All women were then contacted in 1998–99 with a validated postal questionnaire to collect information on incident fractures and potential confounding factors including medication use. All fractures were confirmed by assessment of images and radiology reports by a research nurse. Cox proportional hazards models were used to explore the risk of incident fracture and results expressed as gradient of risk (GR) and 95% CI. Associations were adjusted for age, body-mass index, alcohol consumption, smoking, hormone replacement therapy, medications, and history of fracture. This study was approved by the Southampton Joint Ethics Committee. Findings674 women were recruited and 443 responded to the questionnaire. 55 women (12%) reported a fracture. In fully adjusted models, femoral neck BMC and BMD were similarly predictive of incident fracture (GR 1·64, 95% CI 1·19–2·26 [p=0·002] and 1·76, 1·19–2·60 [p=0·005], respectively). By contrast, femoral neck bone area was not associated with incident fracture (1·15, 0·88–1·50; p=0.32). Similar results were found with bone indices at the lumbar spine and whole body. InterpretationBMC and BMD seem to predict incident fracture with similar gradients of risk, even after adjustment for body size. These findings suggest that factors in early life that are associated with total skeletal mineralisation are likely to have implications for adult fracture risk. FundingMedical Research Council; British Heart Foundation; Arthritis Research UK; National Osteoporosis Society; International Osteoporosis Foundation; National Institute for Health Research (NIHR) Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton NHS Foundation Trust; NIHR Musculoskeletal Biomedical Research Unit, University of Oxford.

Calcium turnover and nutrition through the life cycle.

Ca nutritional requirements and bone Ca turnover can be assessed using numerous techniques. Among these techniques are bone mass measurements, tracer kinetic studies, bone histomorphometry and biochemical studies. Stable-isotope-based kinetic studies offer unique advantages in their ability to assess both Ca absorption and turnover. This approach is safe and readily applicable to subjects of all ages. Ca is essential for growth and maintenance of bone mineral throughout life. During pregnancy, increased intestinal absorption of Ca by the mother provides much of the Ca supplied to the fetus. During infancy, Ca supplied in human milk is primarily derived from maternal bone stores, which are quickly replenished during and after weaning. Early childhood is a time of relatively slow bone growth, with a rapid increase occurring during puberty. Recent kinetic studies demonstrate an increase in both Ca absorption and bone Ca deposition associated with early puberty. Bone Ca deposition reaches a maximum in females shortly before menarche. At that time the bone Ca deposition rate is approximately five times that of adulthood. The decline in bone Ca deposition rate is gradual after menarche. Ca absorption from the diet shows a gradual decline in adulthood as well. Ca supplementation, in the presence of adequate vitamin D, is effective in enhancing bone mineral content in childhood and in helping to maintain bone mineral content in adults. Maintaining adequate Ca nutriture throughout life may be necessary to minimize the risk of bone-loss disorders.

Birth weight is more important for peak bone mineral content than for bone density: the PEAK-25 study of 1,061 young adult women

Lower birth weight has a negative association with adult BMC and body composition in young adult Swedish women. The aim of this study was to evaluate the influence of birth weight on peak bone mass and body composition in a cohort of 25-year-old women. One thousand sixty-one women participated in this cross-sectional population-based study using dual energy X-ray absorptiometry (DXA) to assess bone mineral content (BMC), bone mineral density (BMD), and body composition (total body (TB), femoral neck (FN), total hip (TH), lumbar spine L1-L4 (LS), and lean and fat mass). Birth weight data was available for 1,047 women and was categorized into tertiles of low (≤3,180 g), intermediate (3,181-3,620 g), and high (≥3,621 g) birth weight. Significant correlations were observed between birth weight and TB-BMC (r=0.159, p<0.001), FN-BMC (r=0.096, p<0.001), TH-BMC (r=0.102, p=0.001), LS-BMC (r=0.095, p=0.002), and lean mass (r=0.215, p<0.001). No correlation was observed between birth weight and BMD. The estimated magnitude of effect was equivalent to a 0.3-0.5 SD difference in BMC for every 1 kg difference in birth weight (151 g (TB); 0.22 g (FN); 1.5 g (TH), 2.5 kg TB lean mass). The strongest correlations between birth weight and BMC occurred in women with lowest birth weights, although excluding women who weighed<2,500 g at birth, and the correlation remained significant although slightly weaker. Women with lower birth weight have lower BMC and less lean and fat mass at the age of 25, independent of current body weight. Lower birth weight has a greater negative influence on bone mass than the positive influence of higher birth weight.

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.

Does birthweight predict bone mass in adulthood? A systematic review and meta-analysis

This systematic review and meta-analysis assessed the strength and magnitude of the association between birthweight and adult bone mass. Higher birthweight was associated with higher bone mineral content of the spine and hip in adult men and women at ages between 18 and 80 years across a range of settings. The aim of this review was to assess the strength and magnitude of the association between early size and adult bone mass. Systematic review and meta-analysis of studies that assessed the association between birthweight or weight at 1 year, and bone mineral content (BMC) or bone mineral density (BMD) in adulthood. Fourteen studies met inclusion criteria. Nine assessed the relationship between birthweight and lumbar spine BMC, most showing that higher birthweight was associated with greater adult BMC. Meta-analysis demonstrated that a 1 kg increase in birthweight was associated with a 1.49 g increase in lumbar spine BMC (95% CI 0.77-2.21). Birthweight was not associated with lumbar spine BMD in 11 studies. In six studies, considering the relationship between birthweight and hip BMC, most found that higher birthweight was associated with greater BMC. Meta-analysis demonstrated that a 1 kg increase in birthweight was associated with a 1.41 g increase in hip BMC (95% CI 0.91-1.91). Seven studies considered the relationship between birthweight and hip BMD and, in most, birthweight was not a significant predictor of hip BMD. Three studies assessing the relationship between weight at 1 year and adult bone mass all reported that higher weight at one was associated with greater BMC of the lumbar spine and hip. Higher birthweight is associated with greater BMC of the lumbar spine and hip in adulthood. The consistency of these associations, across a range of settings, provides compelling evidence for the intrauterine programming of skeletal development and tracking of skeletal size from infancy to adulthood.

Birth weight and adult bone mass: a systematic literature review

This systematic literature review comprised 16 studies. The association of birth weight with bone parameters was much more evident for bone mineral content (BMC) rather than bone mineral density (BMD). This is an important finding since a reduction in BMC is strongly associated with an increased risk of fractures. The purpose of this study was to conduct a systematic literature review of studies that have investigated the association between birth weight (BW) and adult bone mass. The search included English language articles, indexed in MEDLINE, using the key words: ("birth size" OR "birth weight" OR birthweight) AND (osteoporosis OR "bone mass" OR "bone density" OR "bone mineral density" OR "bone mineral content" OR "bone area"). A methodological quality appraisal of the reviewed studies was performed. Sixteen articles were reviewed. Eleven of 13 studies that measured BMC verified a positive effect of BW on this parameter, and nine even after adjustment for adult body size. Among the ten studies that found an unadjusted association between BW and BMD, two reported that the significance remained after adjustment for current body size. Interaction between prenatal and postnatal variables on the determination of adult bone mass was only tested by two studies. The results must be interpreted with caution due to the existence of few papers on the issue, as well as heterogeneous sample characteristics, investigated bone sites, and implemented analysis procedures. The aspects of methodological quality that frequently fail are as follows: representativeness of the planned and actually measured sample as well as proper adjustment for confounding. Based on the amount of accumulated evidence, it is probable that BW have a positive association with adult BMC rather than BMD, which is an important finding for clinical and public health policies since a reduction in BMC is strongly associated with an increased fracture risk.

Early development and osteoporosis and bone health.

Osteoporosis is a skeletal disorder characterized by low bone mass and micro-architectural deterioration of bone tissue with a consequent increase in bone fragility and susceptibility to fracture. Evidence is now accumulating from human studies that programming of bone growth might be an important contributor to the later risk of osteoporotic fracture. Body weight in infancy is a determinant of adult bone mineral content, as well as of the basal levels of activity of the growth hormone/insulin-like growth factor-1 (GH/IGF-1) and hypothalamo-pituitary-adrenal (HPA) axes, and recent work has suggested a central role for vitamin D. Epidemiological studies have shown that maternal smoking and nutrition during pregnancy influence intrauterine skeletal mineralization. Childhood growth rates have been directly linked to the risk of hip fracture many decades later, and now evidence is emerging from experimental animal studies that support these observational data. Recent studies have also highlighted epigenetic phenomena as potential mechanisms underlying the findings from epidemiological studies.

Body size from birth to adulthood and bone mineral content and density at 31 years of age: results from the northern Finland 1966 birth cohort study

The purpose of this study was to evaluate the association between body size from birth to adulthood and bone mineral content (BMC) and bone mineral density (BMD) at the age of 31 years in a longitudinal study of the Northern Finland birth cohort for 1966. Data were collected at birth, 1, 14, and 31 years. This analysis was restricted to a subsample of individuals (n =1,099) for whom the BMC (g) and BMD measurements (g/cm(2)) were performed on the distal and ultradistal radius by dual-energy X-ray absorptiometry (DXA) at the age of 31 years. Determinants of low BMC and BMD were analyzed using multivariate logistic regression. Growth retardation at birth, being underweight (BMI < or =20.0 kg/m(2)) at 31 years, and having a low calcium intake at 31 years were associated independently with low BMD at 31 years. Additionally, the proportion of subjects with low BMD was higher among those who had low standardized body weight (< or =1 SD) both at birth and at 14 years, and both at 14 and 31 years. Body weight at 31 years was the strongest associating factor of BCM at 31 years. Growth retardation at birth has long-lasting effects on adult bone mineral content and density of the distal and ultradistal radius independently of later body size, although adult body weight seems to be a most important determinant of BMC at the age of 31 years. Thinness and a low calcium intake are associated with low bone mineral content and density at 31 years of age. Further studies are needed to evaluate if these groups are at increased risk of osteoporosis in old age.

The developmental origins of osteoporotic fracture.

Undernutrition and other adverse influences arising in fetal life or immediately after birth have a permanent effect on body structure, physiology and metabolism. Evidence is now accumulating from human studies that programming of bone growth might be an important contributor to the later risk of osteoporotic fracture. Body weight in infancy is a determinant of adult bone mineral content, as well as of the basal levels of activity of the GH/IGF-1 and HPA axes, and recent work has suggested a central role for vitamin D. Epidemiological studies have suggested that maternal smoking and nutrition during pregnancy influence intrauterine skeletal mineralization. Finally, childhood growth rates have been directly linked to the risk of hip fracture many decades later. Further work is needed to use this approach to develop novel therapeutic and preventative strategies to reduce the burden of osteoporotic fractures in the population.

Does bone mineralization reflect economic conditions? An examination using a national US sample

Background: Bone density is the most important determinant of osteoporotic fractures, which lead to significant morbidity, disability and mortality for older persons, particularly women. Sensitive periods for bone mineralization in infancy, childhood and adolescence overlap with those for height attainment. After peak density is reached in early adulthood, there is age-related decline. We ask whether bone density, as height, reflects economic conditions. Subjects and methods: Using the third National Health and Nutrition Examination Survey, a probability sample of the US population which over-sampled Blacks and Mexican Americans, we examine the associations between adult bone mineral content (BMC) adjusted for bone and body size and three economic indicators: education, height and the poverty income ratio (PIR). We compare four groups: US-born Whites, Blacks and Mexican Americans and Mexican-born Mexican Americans. Results: Education is positively associated with BMC only for White women, although there are similar, non-significant associations for Black women and White and Black men. For women, BMC is more strongly associated with height for Mexican Americans, especially the Mexican-born, than for Whites. For men, the only significant association is a negative one with education for men born in Mexico. PIR is not significantly associated with BMC, although there is pattern of lower income being associated with lower BMC for Whites and Blacks and higher BMC for Mexican Americans. Conclusion: Bone density does not reflect economic conditions as strongly or consistently as does physical stature. However, for women there is evidence that lower economic status in childhood or adolescence is associated with lower bone density.

Growth and bone mineralization of young adults weighing less than 1500 g at birth.

Preterm infants are at risk for suboptimal growth and bone mineralization compared to infants born at term but long-term outcomes into early adulthood are unclear. To determine (1) if growth and nutrition in the first year of life significantly predict the outcomes measured at adulthood and (2) whole body and regional bone mineral content (BMC) of young adults who were born preterm and weighing <1500 g. In this descriptive follow-up study, subjects were born preterm and weighing <1500 g (n=25, 17.2+/-1.2 years of age) and originally participated in a 1-year follow-up study of infant growth or subjects born at term (n=25, 17.3+/-1.4 years of age). In the preterm group, relationships of growth and nutrition in the first year of life with adult anthropometry and BMC were identified using correlation and regression analysis. Birth groups were compared for measurements of anthropometry and whole body and regional BMC obtained at adulthood using t-tests. After correcting for the effects of bone area using regression, rate of weight gain had a positive relationship and days to regain birth weight a negative relationship to adult BMC. Young adults, born preterm, were significantly shorter with lower whole body BMC than of those born at term, but BMC was appropriate for size. Growth early in life predicts subsequent attainment of growth and bone mass. Premature birth results in lower attainment of height achieved by young adult age but bone mass is appropriate for body size.

Bone growth from 11 to 17 years: relationship to growth, gender and changes with pubertal status including timing of menarche

The tempo and change in bone growth during puberty in relation to physical growth is described in a cohort of 56 boys and 52 girls. Distal forearm bone width, mineral content and volumetric density, anthropometry and pubertal status were measured at ages 11, 13, 15 and 17 y, and bone age at 17 y. Bone width and mineral content increased independently with age for each pubertal stage. Volumetric density fell during early puberty and then increased rapidly. Maximal increase of all bone variables occurred earlier in girls than in boys and earliest for bone width, then mineral content, then density. In girls most change occurred in the 12 mo before and after menarche. The degree of tracking was similar to that for height. Bone growth followed physical growth but at a slower tempo. By age 17 y boys had attained 86% of the reference adult bone mineral content and volumetric density; girls had attained 93% of the reference adult bone mineral content and 94% of volumetric density. Those skeletally mature at 17 y had greater mineral content and volumetric density. To maximize peak bone mass, modifiable environmental factors should be optimized before the onset of puberty and be maintained throughout this period of rapid growth and beyond attainment of sexual maturity.

Factors affecting bone density in young adults

A 14-y follow-up of 581 children who took part in a randomized controlled trial of the effect of a milk supplement on growth of children was conducted to investigate the supplement's effect on adult bone mineral content (BMC) and density (BMD). BMC and BMD of the nondominant forearm were measured by single-photon absorptiometry in 371 subjects (64%) aged 20-23 y, at a proximal site (shaft of radius and ulna) and at a distal site near the wrist. BMCs and BMDs tended to be higher in the intervention group (NS). Cross-sectionally, BMD was positively associated with body weight (P less than 0.01) in both sexes; inversely associated with alcohol consumption (P less than 0.05), and positively with manual occupation (NS) in men; positively associated with current intakes of calcium (P less than 0.05), vitamin D (P less than 0.01), and sports activity during adolescence (P less than 0.01), and inversely with parity (NS) in women. In multiple linear-regression analysis body weight and sports activity during adolescence were stronger determinants of female BMD than was diet.

Bone Mineral Content in Infants-Reply

In Reply .—We do not believe that BMC and total body calcium are comparable, nor are they intended to be. Bone mineral content in adults is highly correlated to total body calcium in cross-sectional studies in which there is no longitudinal bone growth component to total body calcium. 1 During growth, BMC increases at the diaphysis due to increased physical mineral (grams per cubic centimeter) and by growth in width and cortical thickness at the measurement site. Total body calcium includes not only diaphysis but also other sites from diaphysis to epiphysis. Consequently, total body calcium increases as a function not only of increased mineral density, bone width, and cortical thickness but also of longitudinal bone growth. With reference to what BMC is and how it can be related to total body weight, BMC is a linear density that is the equivalent of grams of calcium per length of