Bone mineral content in black pre-schoolers: normative data using single photon absorptiometry

Blood Lead Level Is Negatively Associated With Bone Mineral Density in U.S. Children and Adolescents Aged 8-19 Years

CONTEXT

The relationship of lead (Pb) exposure with bone health in children and adolescents remains controversial.

OBJECTION

We aimed to investigate the association of blood lead levels (BLL) with bone mineral density (BMD) in American children and adolescents using data from the National Health and Nutrition Examination Survey (NHANES), 2005-2010.

METHODS

We analyzed 5,583 subjects aged 8-19 years (mean age, 13.49 ± 3.35 years) from the NHANES 2005-2010. BLL was tested using inductively coupled plasma mass spectrometry. BMD was measured by dual-energy X-ray absorptiometry (DXA) at the lumbar spine, total femur, and femur neck. Multivariate linear regression models were used to explore the association between BLL and BMD, adjusting for age, gender, race/ethnicity, poverty income ratio (PIR), body mass index (BMI), serum calcium, and serum phosphorus.

RESULTS

BLL was negatively correlated with BMD at different sites of interest in children and adolescents. For every 1mg/dl increase in BLL, the BMD of the total spine, total hip, and femoral neck decreased by 0.011 g/cm², 0.008 g/cm², and 0.006 g/cm². In addition, Pb affected the lumbar spine more than the femur. The effect estimates were stronger in girls than boys at the lumbar spine (P for interaction= 0.006). This negative association remained significant in American children and adolescents after excluding individuals with BLL more than 3.5 ug/dl.

CONCLUSION

Our study indicates that BLL is negatively correlated with BMD at different sites of interest in children and adolescents aged 8-19 years, even in the reference range. More research is needed to elucidate the relationships between Pb and bone health in children and adolescents, including specific mechanisms and confounding factors like race/ethnicity, gender, and age.

Effects of lead and cadmium co-exposure on bone mineral density in a Chinese population

It has been indicated that both cadmium (Cd) and lead (Pb) may have adverse effects on the bone. However, most studies have only focused on a single factor. The primary and main and interactive effects of Cd and Pb on bone mineral density (BMD) in a Chinese population were observed in this study. A total of 321 individuals (202 women and 119 men), aged 27 years and older, living in control and polluted areas, were recruited to participate in this study. The BMD was measured through dual energy X-ray absorptiometry (DXA) at the proximal radius and ulna. The samples of urine and blood were collected to determine the levels of Cd and Pb in the urine (UCd and UPb) and blood (BCd and BPb). The Cd and Pb levels of people living in the polluted area were significantly higher than those living in the control area (p<0.05). The BMD of women living in polluted area was significantly lower than that of women living in the control area (p<0.05). Furthermore, the BMD decreased with increasing of BCd (p<0.05), BPb and UPb in women. The likelihood of low BMD was associated with higher BCd in women (OR=2.5, 95% CI: 1.11-5.43) and BPb in men (OR=4.49, 95% CI: 1.37-14.6). The relative extra risk index of low BMD for female and male subjects with both high levels of BCd and BPb was 0.45 and 1.16, respectively. This study strengthens previous evidence that cadmium and lead may influence the bone and also demonstrates that cadmium and lead may have interactive effects on BMD.

The association between blood lead levels and osteoporosis among adults--results from the third national health and nutrition examination survey (NHANES III)

BACKGROUND

Osteoporosis is a reduction in bone mass sufficient to increase the risk of fracture. Lead exposure during childhood may be a risk factor for low bone mineral density (BMD). Basic-science research demonstrates that lead exposure is associated with a decrease in BMD in animals. However, human studies are limited.

OBJECTIVE

Our objective was to conduct a secondary analysis of a national database to explore the association between lead exposure and osteoporosis in adult humans.

METHODS

In this study we used data from the Third National Health and Nutrition Examination Survey (NHANES III). We analyzed subjects who were >/= 50 years of age. A concurrent venous blood lead level defined lead exposure. The primary outcome variable was the BMD of the total hip. We conducted analyses on four groups: non-Hispanic white men, non-Hispanic white women, African-American men, and African-American women. We conducted bivariate analyses between covariates known to be associated with bone density (i.e., age, body mass index, calcium intake, ethanol/tobacco consumption, physical activity, socioeconomic status) and the total hip BMD. The significant covariates were introduced into analysis of covariance to determine the association between BMD and blood lead level tercile.

RESULTS

The adjusted mean total hip BMD among non-Hispanic white males with a blood lead level in the lowest tercile versus the highest tercile was 0.961 g/cm(2) and 0.934 g/cm(2), respectively (p < 0.05). We also found a similar association among white females, but the difference was marginally significant (0.05 < p < 0.10).

CONCLUSIONS

We found a significant inverse association between lead exposure and BMD, but only among white subjects. However, because of the cross-sectional design of NHANES, we cannot make inferences about the temporal sequence of this association. With the large number of adults who had lead exposure in the past and the morbidity associated with osteoporosis, further inquiry is necessary on the possible casusal association between lead exposure and osteoporosis in humans.

Marginal Zinc Deficiency Exacerbates Bone Lead Accumulation and High Dietary Zinc Attenuates Lead Accumulation at the Expense of Bone Density in Growing Rats

Environmental lead exposure is associated with reduced bone growth and quality, which may predispose to osteoporosis. Zinc supplementation may reduce lead accumulation; however, effects on bone development have not been addressed. Our objective was to investigate the effects of marginal zinc (MZ) and supplemental zinc (SZ) intakes on bone lead deposition and skeletal development in lead-exposed rats. In a factorial design, weanling Sprague-Dawley rats were assigned to MZ (8 mg/kg diet); zinc-adequate control (CT; 30 mg/kg); zinc-adequate, diet-restricted (DR; 30 mg/kg); or SZ (300 mg/kg) groups, with and without lead acetate-containing drinking water (200 mg Pb/l) for 3 weeks. Excised femurs were analyzed for bone mineral density (BMD) by dual-energy x-ray absorptiometry, morphometry, and mineral content. MZ had higher femur lead and lower femur zinc concentrations and impaired skeletal growth and mineralization than CT. DR inhibited growth but did not result in higher femur lead concentrations than CT. SZ had higher femur zinc and lower femur lead concentrations than the other treatments. DR and SZ had impaired BMD versus CT and MZ. Lead also retarded skeletal growth and impaired BMD, but an interaction between lead and MZ was only found for femoral knee width, which was lower in MZ exposed to lead. In summary, while MZ deficiency exacerbated bone lead concentration, it generally did not intensify lead toxicity. SZ was protective against bone lead but was detrimental to BMD, suggesting that the optimal level of SZ to reduce lead absorption, while supporting growth and bone development, requires further investigation.

The association between environmental lead exposure and bone density in children

Osteoporosis is a decrease in bone mineral density (BMD) that predisposes individuals to fractures. Although an elderly affliction, a predisposition may develop during adolescence if a sufficient peak BMD is not achieved. Rat studies have found that lead exposure is associated with decreased BMD. However, human studies are limited. We hypothesized that the BMD of children with high lead exposure would be lower than the BMD of children with low lead exposure. We collected data on 35 subjects; 16 had low cumulative lead exposure (mean, 6.5 microg/dL), and 19 had high exposure (mean, 23.6 micro g/dL). All were African American; there was no difference between the groups by sex, age, body mass index, socioeconomic status, physical activity, or calcium intake. Significant differences in BMD between low and high cumulative lead exposure were noted in the head (1.589 vs. 1.721 g/cm2), third lumbar vertebra (0.761 vs. 0.819 g/cm2), and fourth lumbar vertebra (0.712 vs. 0.789 g/cm2). Contrary to our hypothesis, subjects with high lead exposure had a significantly higher BMD than did subjects with low lead exposure. This may reflect a true phenomenon because lead exposure has been reported to accelerate bony maturation by inhibiting the effects of parathyroid hormone-related peptide. Accelerated maturation of bone may ultimately result in a lower peak BMD being achieved in young adulthood, thus predisposing to osteoporosis in later life. Future studies need to investigate this proposed model.

Bone ultrasound velocity curves of newly born term and preterm infants

BACKGROUND

Ultrasound velocity (speed-of-sound [SOS]) has been proposed as a non-invasive method of evaluation of bone status in infants. We hypothesized that SOS correlates with both gestational age and birth weight.

METHODS

We measured SOS within the first 96 hours of life at the right tibial midshaft location in 73 neonates ranging in gestational age from 25 to 41 weeks, and in birth weight from 825 to 3880 grams. We used the Sunlight Omnisense 7000p device (Tel Aviv, Israel). Results are expressed as meanS +/- 1 SD; statistical analyses included linear regression and computation of 95% CI regression lines; p<0.05 was considered significant.

RESULTS

There was, as hypothesized, a significant correlation between gestational age (or birth weight) and SOS. There were no significant differences between males and females. Ninety-five percent confidence intervals were established.

CONCLUSIONS

These data may be used as reference ranges for further studies.

Endocrine complications in pediatric patients with acute lymphoblastic leukemia

Endocrine complications of therapy for acute lymphoblastic leukemia (ALL) are common and are potentially debilitating both during and after therapy. Growth velocity slows during therapy for ALL, especially during the first year; however, children who do not receive cranial irradiation usually reach normal adult height. While growth hormone deficiency generally occurs in patients who have received 24Gy of cranial irradiation, it may also develop in those treated with lower doses (18Gy) of cranial radiation or with only high-dose methotrexate. Obesity commonly occurs during therapy and persists after completion of therapy. Osteopenia can occur early during therapy for ALL and can persist for many years. Adrenal insufficiency should be suspected in any child who has recently received glucocorticoid therapy, and stress doses of steroid should be administered in the event of metabolic stress. Screening of urine is useful for early detection of hyperglycemia during therapy with glucocorticoids and L-asparaginase. The syndrome of inappropriate secretion of anti-diuretic hormone is usually associated with vincristine therapy and may be aggravated by concurrent use of azole antifungals. Finally, patients who have received 18 or 24Gy of cranial irradiation may have clinical or subclinical deficiencies of thyroid hormones.

Whole body bone, fat and lean mass in children: comparison of three ethnic groups

We measured whole body bone, fat and lean mass, by dual-energy x-ray absorptiometry, of third-grade children in a suburban public school district adjacent to Detroit. Of 1,340 eligible children, 773 participated. Using U.S. Census categories, parents identified their children as black/African-American (57%), white (38%), or one of several other categories (5%). Some of the participants also identified with a relatively large Middle Eastern subgroup (Chaldeans). Of the 773 participants, 734 are included in this report (71 Chaldeans, 226 whites, and 437 black/African-Americans; other categories are omitted). We describe body size, body composition, and physical activity levels in the three groups. The Chaldean and black children have significantly higher average whole body bone mineral content (BMC) than whites (P > 0.05), but are not different from each other. Lean mass and height are significantly greater for Chaldeans and blacks than for whites. The ratio of BMC to height was also significantly greater in Chaldeans and blacks compared with whites. Chaldeans have a significantly higher weight and fat mass than either the black or white children, and report significantly less physical activity than either the white or the black children. The higher bone mass among the Chaldean children may be partially explained by their greater body mass, but there is no readily apparent explanation for the observed ethnic differences in body size. We cannot exclude genetic or environmental factors not evaluated in this observational study. Our unexpected finding that Chaldean children, when analyzed as a separate group, are more similar in body composition to black/African-American than to white children contributes to a growing body of literature indicating that the uncritical use of "race" categories may obscure rather than facilitate the identification of population differences.

The accumulation of whole body skeletal mass in third- and fourth-grade children: effects of age, gender, ethnicity, and body composition

The purpose of this longitudinal study is to describe bone mass and body composition, and the annual changes in these measurements, among third grade students recruited from a suburban school district. Whole body bone mineral content (WBBMC), bone mineral density (WBBMD), fat, and lean mass were measured by dual-energy X-ray absorptiometry. Bone mass in the lumbar spine (LBMC) region of the whole body scan was also utilized. 773 students (38% white, 57% black, 5% other) had baseline visits; 561 had a second measurement a year later. At baseline, black children have significantly higher WBBMC, WBBMD, height, and lean mass than whites. Black males, but not black females, have a greater LBMC. There are no significant gender differences in body size, WBBMC, or WBBMD, although girls have a greater LBMC and fat mass, and boys have a higher lean mass. Most of these differences persist in visit 2. The annual change in bone and lean mass is greater in blacks. Stepwise linear regression analyses of bone mass on body size, gender, and ethnicity and their interactions indicate that log-transformed weight explains most of the variance in both WBBMC and WBBMD (multiple r2 = 0.90 and 0.64, respectively). There are significant black/white differences in intercepts and slopes. Other variables explain only another 1%-2% of the variance. The strongest Pearson correlations are between changes in bone mass and changes in lean mass and log-transformed weight (r ranging from 0.62 to 0.84, p = 0.0001). We conclude that there is a significant black/white, but not male/female difference in whole body bone mass and bone density before puberty. Ethnic and gender differences in bone and body composition suggest that the lean component may contribute to a greater peak bone mass in blacks vs. whites, and perhaps in males vs. females.

Risk for osteoporosis in black women

Models of involutional bone loss and strategies for the prevention of osteoporosis have been developed for white women. Black women have higher bone densities than white women, but as the black population ages there will be an increasingly higher population of black women with osteoporosis. Strategies should be developed to reduce the risk of black women for fragility fractures. Dual energy X-ray absorptiometry measurements of the total body, femur, spine, and radius were performed on 503 healthy black and white women aged 20-80 years. Indices of bone turnover, the calcitrophic hormones, and radioisotope calcium absorption efficiency were also measured to compare the mechanisms of bone loss.The black women had higher BMD values at every site tested than the white women throughout the adult life cycle. Black women have a higher peak bone mass and a slightly slower rate of adult bone loss from the femur and spine, which are skeletal sites comprised predominantly of trabecular bone. Indices of bone turnover are lower in black women as are serum calcidiol levels and urinary calcium excretion. Serum calcitriol and parathyroid hormone levels are higher in black women and calcium absorption efficiency is the same in black and white women, but dietary calcium intake is lower in black women. Black and white women have a similar pattern of bone loss, with substantial bone loss from the femur and spine prior to menopause and an accelerated bone loss from the total skeleton and radius after menopause. The higher values for bone density in black women as compared with white women are caused by a higher peak bone mass and a slower rate of loss from skeletal sites comprised predominantly of trabecular bone. Low-risk strategies to enhance peak bone mass and to lower bone loss, such as calcium and vitamin D augmentation of the diet, should be examined for black women. The risk vs. benefits of hormonal replacement therapy should be determined, especially in older women.

Total body mineral mass measured with dual photon absorptiometry in healthy children

Using dual photon absorptiometry, bone mineral content (BMC) and bone mineral density (BMD) of the total body and the lumbar spine were assessed in 97 healthy, Caucasian children aged 3-14 years. Excellent correlations were found between BMC and BMD on the one hand and age, body height and body weight on the other. No differences were found between boys and girls. There was a strong correlation between lumbar spine measurement as compared to those of the total body. Regression equations for total body and the different parts of the skeleton were calculated with either BMC or BMD as the dependent variable, and age, body height and body weight as independent variables. High variation coefficients were obtained in these multiple regressions, except for the head. For total body BMC and total body BMD, growth charts were constructed using Tanner and Whitehouse data on body height and body height and body weight. Conclusions. The increase in total body mineral content is an important feature of normal growth. Normal data for BMC and BMD in childhood are essential for bone mineralisation abnormalities in paediatric patients.

Reference data for bone mass, calciotropic hormones, and biochemical markers of bone remodeling in older (55-75) postmenopausal white and black women

From a random sample of our institution's health maintenance organization (HMO), we recruited 250 white women and 112 black women, aged 55-75, all of whom were 10 or more years postmenospause with minimal estrogen exposure and free of osteoporosis, other metabolic bone disease, and medical, surgical, or therapeutic situations that may influence bone loss. Bone mass was measured in the radius, spine, and femur by DXA and in L1 by QCT. Serum samples were analyzed for parathyroid hormone, calcidiol, calcitriol, osteocalcin, and bone alkaline phosphatase and urine samples analyzed for creatinine, calcium, and hydroxyproline. Mean Z score, based on published reference data for forearm and femoral neck BMD in the white women, was not significantly different from zero, but mean Z score at the lumbar spine was 0.6 (p < 0.001), 17.2% of the individual values being > 2.0. In normal white women (BMI < 27.3, n = 143), Z score was still > 2.0 in 10.3%, suggesting that the upper bound of the published reference interval may be too low. After adjustment for body mass index, BMD was greater in the forearm (9.8%), spine (8.7%), and femoral neck (14.7%) in black women (p < 0.001 at all sites). At L1, adjusted BMC in the black women was 37.4% greater than in the white women (p < 0.001). Serum calcidiol was significantly lower and serum PTH and calcitriol significantly higher in the black women. Despite this, biochemical markers of bone resorption and formation were significantly lower in the black women. We conclude that skeletally healthy older black women have a greater bone mass and lower rates of bone remodeling than a comparable group of white women. These data can serve as reference intervals for the variables measured.