John N. Fordham

Ethnic and gender differences in body fat in British schoolchildren as measured by DXA

Background: There are known to be ethnic differences in body composition in adults which are related to ethnic differences in adult disease. Objectives: To evaluate gender and ethnic differences in percentage body fat in British schoolchildren and to compare these differences with classification of obesity using body mass index (BMI) criteria. Design: A cross-sectional study of 1251 healthy children and adolescents aged 5–18 years from white, South Asian and African-Caribbean ethnic groups. Percentage body fat was determined by dual x ray absorptiometry and the subjects classified using BMI criteria for overweight and obesity. Results: Significant gender differences in percentage body fat were seen, with girls having higher values from the age of 5 years. Girls had 3.8% higher percentage body fat at 5 years of age increasing to 12.9% at 18 years of age. Significant ethnic differences were found, with South Asian girls and boys having the highest percentage body fat from 5 and 7 years of age, respectively. These differences increased with age, being most significant in the teenage years. Although South Asian girls and boys were over-represented in the group containing children with more than 25% body fat (p<0.0001, χ2 test), African-Caribbean subjects were more likely to be classified as obese using BMI criteria. Conclusions: There are clear gender and ethnic differences in percentage body fat in British schoolchildren which may relate to known differences in the risk of type 2 diabetes in adolescence and adulthood. BMI criteria for defining overweight and obesity do not accurately identify ethnic differences in body fat.

Peripheral dual-energy X-ray absorptiometry in the management of osteoporosis: the 2007 ISCD Official Positions

Peripheral assessment of bone density using photon absorptiometry techniques has been available for over 40 yr. The initial use of radio-isotopes as the photon source has been replaced by the use of X-ray technology. A wide variety of models of single- or dual-energy X-ray measurement tools have been made available for purchase, although not all are still commercially available. The Official Positions of the International Society for Clinical Densitometry (ISCD) have been developed following a systematic review of the literature by an ISCD task force and a subsequent Position Development Conference. These cover the technological diversity among peripheral dual-energy X-ray absorptiometry (pDXA) devices; define whether pDXA can be used for fracture risk assessment and/or to diagnose osteoporosis; examine whether pDXA can be used to initiate treatment and/or monitor treatment; provide recommendations for pDXA reporting; and review quality assurance and quality control necessary for effective use of pDXA.

Identification of women with reduced bone density at the lumbar spine and femoral neck using BMD at the os calcis.

Abstract: We assessed the clinical usefulness of bone density measurements at the os calcis as a screening tool to identify patients with low bone density at the lumbar spine and femoral neck. Bone mineral density (BMD) was recorded in 443 women (mean age 60 years) referred to a bone densitometry service. Measurements were made at the lumbar spine and femoral neck using a Lunar DPXL and at the right os calcis using a Peripheral Instantaneous X-ray Imaging (PIXI) dual-energy X-ray absorptiometry system. Average T-scores derived using the manufacturer”s data were: 1.59 for the lumbar spine, −1.41 for the femoral neck and −0.87 for the os calcis. The prevalence of osteoporosis using WHO criteria (T-scores of −2.5 or less) was 36% for the lumbar spine or femoral neck but only 9.7% for the os calcis. BMD of the os calcis correlated with that at the lumbar spine (r= 0.69, p<0.001) and femoral neck (r= 0.67, p<0.001). The area under the receiver operator characteristics curve was 0.836 (standard error 0.020) for the os calcis related to osteoporosis at the lumbar spine or femoral neck. Optimal accuracy was obtained at a T-score of ≤−1.3 (BMD 0.39 g/cm2) when the sensitivity was 69.6% (95% confidence interval 65.3, 73.9%) and specificity 82.6% (95% confidence interval 79.1, 86.1%). However, the probability of diagnosing low bone density from a given BMD at the os calcis varied by age and site scanned. Accordingly, for informing management strategies, the choice of a single cutoff BMD at the os calcis may not be appropriate and several thresholds may be adopted based on age, the site of interest (lumbar spine or femoral neck) and consideration of associated clinical features. Thus, the use of heel bone density scanners could reduce the number of axial bone density measurements required. The advantages of portability, low cost and shorter scan times should reduce the cost of detection and provide a greater opportunity for identification of women at risk of fracture.

Osteoprotegerin, RANKL and bone turnover in postmenopausal osteoporosis

Background Osteoprotegerin (OPG) and receptor activator of nuclear factor κ B ligand (RANKL) play a critical role in the regulation of bone turnover, but the relative importance of these two cytokines in the pathogenesis of postmenopausal osteoporosis is controversial. Aim To investigate the relationship between circulating levels of OPG, RANKL, bone turnover and bone mineral density (BMD) in postmenopausal women. Methods A cross-sectional study of 185 women with osteoporosis and 185 age- and sex-matched control subjects was undertaken. Measurements were made of plasma OPG, RANKL, interleukin-6 (IL-6), sex steroids, calciotropic hormones, biochemical markers of bone turnover, BMD and anthropometry. Health questionnaires were administered. Results Plasma RANKL was significantly higher (p<0.0001) in women with osteoporosis (0.66±0.67 pmol/l) than in control subjects (0.37±0.38 pmol/l), as was plasma OPG (18.70±9.70 pmol/l in women with osteoporosis, 10.44±5.85 pmol/l in control subjects; p<0.0001). OPG/RANKL ratio was higher in women with osteoporosis (51.3) than in control subjects (36.6). The women with osteoporosis also had significantly higher biochemical markers of bone turnover, IL-6 and parathyroid hormone and lower 25-hydroxyvitamin D and oestradiol than the control subjects. Multiple regression analysis showed that lumbar spine and femoral neck BMD in postmenopausal women were best predicted by OPG and RANKL, giving an R2 value of 15.5% and 14.9%, respectively. Conclusions This study indicates that the circulating levels of OPG and RANKL are inversely related to BMD and contribute to the development of osteoporosis in postmenopausal women.

Plasma vitamin D and cytokines in periodontal disease and postmenopausal osteoporosis

BACKGROUND AND OBJECTIVE Osteoporosis and periodontal disease are chronic diseases, in the pathogenesis of which plasma osteoprotogerin (OPG) and RANKL are important. The study aimed to investigate the relationship between periodontal disease and plasma cytokines, vitamin D and bone mineral density in postmenopausal women with and without osteoporosis. MATERIAL AND METHODS One hundred and eighty-five postmenopausal women with osteoporosis and 185 age- and sex-matched control subjects were recruited. Periodontal disease was subdivided into active or past periodontal disease. Osteoprotegerin, RANKL, 25-hydroxyvitamin D₃ (25OHD), biochemical markers of bone turnover (serum C-terminal telopeptide, CTX), anthropometry and bone mineral density were measured. RESULTS A significantly higher proportion of the women with osteoporosis had active or past periodontal disease or both compared with control subjects (87.6 vs. 37.8%, p < 0.001). Plasma 25OHD was significantly lower (p < 0.001) and RANKL and OPG significantly higher in the women with osteoporosis than in control subjects (p < 0.0001). RANKL, OPG and CTX were significantly higher in women with active periodontal disease than in those without (p < 0.001), as were OPG and CTX in past periodontal disease (p < 0.001). In active and past periodontal disease, 25OHD was significantly lower (p < 0.001). Multiple logistic regression analysis showed that periodontal disease was best predicted by RANKL, 25OHD, C-terminal telopeptide and weight, r² = 10.4%. CONCLUSION Periodontal disease is more common in women with osteoporosis and is associated with lower vitamin D and higher concentrations of RANKL and OPG. Raised cytokines may provide the underlying mechanism that links these two conditions.

Bone density at the os calcis: reference values, reproducibility, and effects of fracture history and physical activity.

Aims: To establish reference values for bone mineral density (BMD) measured at the os calcis (OC) in healthy UK Caucasian children. Secondary objectives were to assess the reproducibility of the measurement and the effects of fracture history and habitual physical activity. Methods: A total of 403 children aged 5–18 were studied. Main outcome measures were: BMDoc measured by peripheral DXA, total BMD measured by whole body axial scanner, age, anthropometry, pubertal status, self-reported fracture history, and physical activity (PA) expressed as a three point score. Results: Complete data were available on 171 girls and 123 boys free of a history of fracture. BMDoc was related positively to age, body size, and total BMD, and could be predicted using a proportional model based on height alone (R2: 65% girls, 77% boys). Mean BMDoc appears to plateau in girls at 15 years and attain a value that concurs with the mean peak value in adult women. The 95% limits of agreement in repeated measures were −0.029 to 0.029 g/cm2 (n = 53). Compared with sedentary children, those doing regular sports or PA for more than five hours a week had an increased BMDoc (by about 0.03 g/cm2 or about 7% of the overall mean). A history of fracture (n = 81) was associated with a reduced BMDoc in boys but not in girls, though our study may have been underpowered for a subgroup analysis. Conclusions: BMDoc can be measured easily and quickly in children older than 5 years and provides an objective measure of areal bone density for clinical and research studies using a reference range derived from its relation to height.

Identification of Men With Reduced Bone Density at the Lumbar Spine and Femoral Neck Using BMD of the Os Calcis

We assessed the utility of os calcis (OC) bone mineral density (BMD) measurements to identify men with low BMD at the lumbar spine (LS) and femoral neck (FN). BMD was measured by dual X-ray absorptiometry (DXA). Receiver operator characteristics (ROC) analysis was applied to determine the risk of osteoporosis at the lumbar spine or femoral neck. [A total of 230 men with an average age of 59 yr were studied.] The most common reasons for referral were fracture (47%) and steroid use (46%). Twenty-six percent were osteoporotic at the LS, 21% at the FN, and 15% at the OC. Optimal classification with respect to osteoporotic measurements at the LS or FN was obtained at an OC T-score of -1.9 (BMD = 0.45 g/cm2). Osteoporosis was only weakly related to a simple cumulative risk factor score, but was strongly related to a T-score OC categorized into quartiles. Regression analysis of BMD on the major risk factors alone explained only 17% of the variance in BMD at the LS and 5% at the FN. The combination of the T-score at the OC, age, and weight provided the best model. BMD OC is superior to risk factors alone in the clinical evaluation and selection of men referred for axial densitometry.