Dual-photon X-ray Absorptiometry Research Articles

Body composition in 85 year-old women: effects of increased physical activity.

This study explores whether regular training alters body composition and resting metabolism in the very old. A total of 55 community-dwelling women, 85 years old, were enrolled in a training group (N = 22) and a control group (N = 33). Training was performed once a week for eight months, and consisted of various exercises with particular attention to movements important for everyday activities. Before, immediately after, and one year after cessation of training, body composition was evaluated both by an impedance measurement and a whole body scan by dual-photon X-ray absorptiometry. Resting metabolism, assessed as energy expenditure at rest, was measured with standardized protocols by analyzing oxygen consumption and carbon dioxide production. Height declined in both groups throughout the study. Immediately after the training period, body weight showed a trend towards reduced levels in the training group, and an opposite trend in the control group. The control group showed an increased body mass index (p < 0.05) related to an increase in fat mass immediately after the training period; these parameters were unaltered in the training group. A reduction in fat free mass (p < 0.05) and bone mineral content (p < 0.05), and unaltered energy expenditure at rest were evident in both groups during the course of the study. These results suggest that regular training can counteract the age-related accumulation of fat in the very old. Physical reactivation, therefore, may possess an important potential for reducing morbidity in the very old by lowering fat mass, and thereby reducing the risk of acquiring several age-related diseases.

Bone mineral density in patients undergoing bone marrow transplantation for myeloid malignancies.

Bone mineral density (BMD) was measured in 23 patients who had undergone bone marrow transplantation (BMT) at the University of Minnesota for myeloid leukemia. The median age at BMT was 22 years (range 3-53) and the median age at assessment of BMD was 27 years (range 4-56). Total body BMD was measured a median of 2 years (range 1-10) after BMT using Dual Photon X-ray Absorptiometry (DEXA). BMD was measured in g/cm2, with results expressed as percent of normal values and as Z (standard deviation) scores. Patients were categorized into two groups (pediatric and adult) according to age at BMT (< or = 18 years vs > 18 years). Total body BMD of patients in the pediatric age group was significantly decreased (median Z-score -0.5) compared to the adult population (median Z-score 0.0, P = 0.03). No association was observed between BMD and time elapsed since BMT, type of conditioning regimen, gonadal function, steroid intake or graft-versus-host disease. Investigation of decreased BMD in children with AML following BMT is needed to determine the metabolic basis, long-term implications, appropriate preventive measures and potential interventions.

Outcomes of obese children and adolescents enrolled in a multidisciplinary health program.

The study was designed to evaluate the impact of a multidisciplinary program on children and adolescents' weight control. Retrospective study regarding changes in relative weight of all patients treated regularly in an out-patient care public service between January 1992 and December 1993. 198 children and adolescents (108 girls and 90 boys; mean age: 9.25y; mean body mass index (BMI): 24.26 kg/m2, range 19.1-40.31). Anthropometric data collected at the visits were obtained until June 30 1994. BMI compared to reference data was used. Dual Photon X-ray Absorptiometry (DEXA) was used for 64 patients, to determine percent body fat. Relative weight at the last visit was significantly lower when compared with initial relative weight for the whole sample. Significantly better outcome of relative weight was obtained when six or more visits occurred for the whole sample, and for girls when the days' interval between visits was shorter than 52 d. Variables such as percent body fat, body shape at the first visit, family obesity pattern, length of obesity and pubertal stage, did not significantly influence the outcome of relative weight for the subjects during the treatment. Results obtained indicated that good outcomes can be obtained in a program using nutrition education focused on small modifications of eating habits in order to avoid excess energy intake. The best predictors of weight improvement for children and adolescents participating in the program were the higher frequency of visits and shorter intervals between them.

Bone mineral density in French Canadian women.

This cross-sectional study investigated bone mineral density (BMD) at the lumbar spine (L2-4) and femoral neck in French Canadian women residing in the Quebec city area. Data collection was initiated in 1988 and completed in 1994. A total of 747 French Canadian Caucasian women (16-79 years of age) with no metabolic bone disease were evaluated. BMD measurements were obtained using dual-photon absorptiometry (DPA) or dual-energy X-ray absorptiometry (DXA). Anthropometric measures such as weight, height and body mass index (BMI) were recorded. Medical files provided information on demographic characteristics, hormonal profile and lifestyle habits. Results show a curvilinear trend of BMD with aging. Furthermore, the peak BMD at the lumbar spine (L2-4) was reached at 29 years followed by a stable phase until 35 years, after which BMD started to decrease. The pattern of bone evolution at the femoral neck was different, peak BMD being achieved earlier, at 21 years, while after age 26 years a significant decrease was already observed. Women older than 60 years showed the lowest BMD. Regression analysis showed that age, weight and height are determinants of BMD at the lumbar spine and explained 33.9% of inter-individual variation. At the femoral neck, 29.1% of variation was explained by age and height only. In conclusion, our data suggest that French Canadian women have a different pattern of bone loss at the femoral neck compared with the lumbar spine, according to their mean BMD values.

Bone mineral density in patients with Crohn's disease during long-term treatment with azathioprine.

To ascertain whether patients with Crohn's disease treated with azathioprine maintained bone mineral mass better than patients treated with steroids alone. Retrospective study. University Hospital of Malmö, Sweden. A total of 59 patients with ileocolonic, ileocaecal or colonic Crohn's disease. Bone mass was assessed by dual photon X-ray absorptiometry at the level of L2-L4. Patients treated with a high lifetime dose of steroids (> 5 g prednisolone) had significantly (P = 0.011) lower Z-score of L2-L4 (-0.87 +/- 1.11; 11 SD) than steroid-treated patients, who had received a low dose of prednisolone (< 5 g) (0.08 +/- 1.16 SD). Azathioprine did not negatively influence the steroid effect on bone mineral density. Azathioprine does not seem to affect bone mineral density by itself. However, by being steroid-saving, it seems to conserve bone mineral mass in patients with Crohn's disease.

Determinants of bone mineral density in postmenopausal white Iowans.

Osteoporosis is a major health problem for older individuals. For women, development of osteoporosis is a function of the accretion of "peak" bone mass in the third decade, age at menopause, and rate of bone loss with aging. Low bone mineral density (BMD) is a major risk factor for osteoporosis and fracture. The purpose of this study was to identify life style, nutritional, medical, and genetic predictors of low BMD in postmenopausal Iowa women. One hundred thirty-four postmenopausal White women ranging in age from 57 to 81 years were included in this case-control study. Bone mineral density was measured at the femoral neck, using dual photon X-ray absorptiometry (Hologic 2000 QDR). Sixty-six women with BMD measurements below 0.68 g/cm2 (the bottom quartile of the BMD distribution in the population from which participants were recruited), and 68 women with values at or above 0.83 g/cm2 (the top quartile of the BMD distribution in the same population) were included. Information about environmental, nutritional, medical, and life style modifiers of BMD was obtained by written questionnaire and telephone interview. To assess familial factors that might influence BMD, we obtained a detailed family history for each participant. In addition, we tested the hypothesis that allelic variation at the Vitamin D receptor (VDR), and the type I collagen gene (COL1A1 and COL1A2) loci influence BMD. Weight, loss of height, age, and age at menopause were strong predictors of BMD in our population. After adjustment for these differences, we found no effect of genotype at the COL1A1, COL1A2, and VDR loci on BMD. Bone mineral density is a complex trait that is influenced by several different modifiers; in the present study, weight was the best predictor of postmenopausal BMD. While several studies suggest that VDR genotype is an important determinant of BMD, we did not find this association in our population, nor did we identify an association between allelic variation at the type I collagen gene loci and BMD. Identification of genes that determine body mass index may provide additional insight into risk factors for low BMD, and osteoporotic fractures.

Resting metabolic rate in obese, premenopausal black women

In the United States, obesity is more prevalent in black than in non-Hispanic white women. Because low resting metabolic rate (RMR) has been suggested as a risk factor for weight gain, we compared RMR in 22 black and 20 white obese [body mass index (BMI; in kg/m2) range: 28.9-48.6 and 26.9-44.1, respectively], weight-stable, premenopausal, nondiabetic women. RMR was measured on two or three different occasions within a 1-wk period. The black and white groups did not differ significantly in age, degree of fitness, BMI, fat mass, or fat-free mass (FFM). In each group, RMR was predicted independently by FFM but not by age, degree of fitness, body fat mass, or body fat distribution. The slopes of the equations predicting RMR from FFM in black and white groups were not significantly different. However, the black women had significantly lower RMRs than the white women after adjustment for FFM measured by five body-composition models: dual-photon X-ray absorptiometry (DXA), hydrodensitometry, total body water, a three-compartment model, a four-compartment model, as well as for the absolute total-body potassium content as a measure of metabolically active FFM. By each analysis, the black women had significantly lower (P < 0.01) FFM-adjusted RMR than the white women; this difference ranged from 671 to 889 kJ/d depending on the body-composition method used to estimate FFM. This could contribute to the difference in the prevalence of obesity in the populations represented by these groups.

Universal standardization of bone density measurements: a method with optimal properties for calibration among several instruments.

The International Dual-Photon X-Ray Absorptiometry (DXA) Standardization Committee (IDSC) conducted a cross-calibration study among three models of DXA machines from three different manufacturers. In that study, 100 subjects were scanned on all three machines. A set of equations were derived to convert bone mineral density (BMD) on each machine to a "standardized BMD" (sBMD) such that sBMD from the same subject derived from different machines would be approximately the same. In a reanalysis of the cross-calibration data, we showed that the conversion method used in the IDSC study did not achieve several optimal properties desirable in such conversions. We derived new conversion equations to sBMD based on minimizing differences among sBMD from the three machines. More important is that the new conversions have no residual bias that was present in the IDSC conversions. The performance of the methods were compared on the cross-calibration data as well as an external data set. We conclude that the IDSC conversions are adequate for clinical use on other machines worldwide, but that researchers should standardize their own machines in a laboratory using the new method.

Ultrasonographic heel measurements to predict hip fracture in elderly women: the EPIDOS prospective study

The ability of ultrasonographic measurements to discriminate between patients with hip fracture and age-matched controls has until now been tested mainly through cross-sectional studies. We report the results of a prospective study to assess the value of measurements with ultrasound in predicting the risk of hip fracture. 5662 elderly women (mean age 80.4 years) had both baseline calcaneal ultrasonography measurements and femoral radiography (dual-photon X-ray absorptiometry, DPXA) to assess their bone quality. Follow-up every 4 months enabled us to identify incident fractures. 115 hip fractures were recorded during a mean follow-up duration of 2 years. Low calcaneal ultrasonographic variables (obtained from measurements of broadband ultrasound attenuation by, and speed of sound through the bone) were able to predict an increased risk of hip fracture, with similar accuracy to low femoral bone mineral density (BMD) obtained by DPXA. The relative risk of hip fracture for 1 SD reduction was 2.0 (95% CI 1.6-2.4) for ultrasound attenuation and 1.7 (1.4-2.1) for speed of sound, compared with 1.9 (1.6-2.4) for BMD. After control for the femoral neck BMD, ultrasonographic variables remained predictive of hip fracture. The incidence of hip fracture among women with values above the median for both calcaneal ultrasound attenuation and femoral neck BMD was 2.7 per 1000 woman-years, compared with 19.6 per 1000 woman-years for those with values below the median for both measures. Ultrasonographic measurements of the os calcis predict the risk of hip fracture in elderly women living at home as well as DPXA of the hip does, and the combination of both methods makes possible the identification of women at very high or very low risk of fracture.

Fall-related factors and risk of hip fracture: the EPIDOS prospective study

Most hip fractures result from falls. However, the role of fall-related factors has seldom been examined. Comparison of the predictive value of these factors with that of bone mineral density (BMD) has important implications for the prevention of hip fractures. We assessed femoral-neck BMD by dual-photon X-ray absorptiometry and potential fall-related risk factors, which included self-reported physical capacity, neuromuscular function, mobility, visual function, and use of medication in 7575 women, aged 75 years or older, with no history of hip fracture recruited at five centres in France. We followed up these women every 4 months to record incident hip fractures. During an average of 1.9 years of follow-up 154 women suffered a first hip fracture. In age-adjusted multivariate analyses, we found four independent fall-related predictors of hip fracture: slower gait speed (relative risk = 1 . 4 for 1 SD decrease [95% Cl 1.1-1.6)]; difficulty in doing a tandem (heel-to-toe) walk (1.2 for 1 point on the difficulty score [1.0-1.5]); reduced visual acuity (2.0 for acuity < or = 2/10 [1.1-3.7]); and small calf circumference (1.5 [1.0-2.2]). After adjustment for femoral-neck BMD, neuromuscular impairment--gait speed, tandem walk--and poor vision remained significantly associated with an increased risk of subsequent hip fracture. With high risk defined as the top quartile of risk, the rate of hip fracture among women classified as high risk based on both a high fall-risk status and low BMD was 29 per 1000 women-years, compared with 11 per 1000 for women classified as high risk by either a high fall-risk status or low BMD; for women classified as low risk based on both criteria the rate was five per 1000. We conclude that neuromuscular and visual impairments, as well as femoral-neck BMD, are significant and independent predictors of the risk of hip fracture in elderly mobile women, and that their combined assessment improves the prediction of hip fractures.

No diffuse osteoporosis in lumbar scoliosis but lower femoral bone density on the convexity

The aims of our study were to find out, in 15 female volunteers with untreated structural lumbar idiopathic scoliosis, through dual-photon X-ray absorptiometry measurements, whether femoral bone mineral density (BMD) was different between the right and the left side and whether this difference was related to scoliosis convexity. We showed that no statistical significant difference between femoral neck BMD measured on both sides of the same patient (p = 0.6). However, neck BMD from the same side as the convexity side was significantly lower than the opposite one.

The effect of regular intramuscular corticosteroid therapy on bone mineral density in rheumatoid patients.

To evaluate the effect of long term regular bolus doses of intramuscular corticosteroid on bone mineral density in rheumatoid patients we undertook a retrospective cross-sectional study of 68 rheumatoid patients. Patients were divided into three groups; those who had received maintenance doses of intramuscular corticosteroid (steroid), those who had been taking regular doses of oral steroid and those who had never received steroid by either route. Bone mineral density (BMD) was measured at the hip and lumbar spine by dual photon X-ray absorptiometry (DEXA). Z scores were calculated for each patient at both sites. There is a statistical difference in Z scores at the hip in both steroid treated groups compared with the no steroid group (p < 0.001). Total steroid was less in the IM treated group compared to the oral steroid group. These results suggest that maintenance therapy with IM steroids produces significant losses of bone mineral density at the hip in rheumatoid patients and that this effect appears to be independent of the total dose.

Bone mineral status in paraplegic patients who do or do not perform standing.

Bone mineral density (BMD) was assessed by dual-photon X-ray absorptiometry at the lumbar spine (L3, L4), the proximal femur and the femoral shaft, and by single-photon absorptiometry at the forearm in 53 patients with complete traumatic paraplegia of at least 1 year's duration and in age- and sex-matched healthy controls. The patients did (n = 38) or did not (n = 15) regularly perform passive weightbearing standing with the aid of a standing device. Compared with the controls, the BMD of paraplegic patients was preserved in the lumbar spine and was markedly decreased in the proximal femur (33%) and the femoral shaft (25%). When considering all patients performing standing, they had a better-preserved BMD at the femoral shaft (p = 0.009), but not at the proximal femur, than patients not performing standing. BMD at the lumbar spine (L3, L4) was marginally higher in the standing group (significant only for L3; p = 0.040). A subgroup of patients performing standing with use of long leg braces had a significantly higher BMD at the proximal femur than patients using a standing frame or a standing wheelchair (p = 0.030). The present results suggest that passive mechanical loading can have a beneficial effect on the preservation of bone mass in osteoporosis found in paraplegics.

The relationship between total body potassium and resting energy expenditure in individuals with paraplegia.

Body composition changes occur with spinal cord injury (SCI): fat-free mass (FFM) decreases and fat mass (FM) increases. FFM has been reported to correlate with resting energy expenditure (REE) in non-SCI individuals. This report addresses the question as to whether REE correlates with measures of FFM in individuals with paraplegia. Twelve males with chronic paraplegia had measurements of total body potassium (TBK), an indicator of lean tissue, by whole body 40K counting, and FFM by dual photon x-ray absorptiometry (FFMDPX). REE was measured using a metabolic cart for exhaled gas analysis. Corrleations between REE and TBK, and REE and FFMDPX were determined. The mean TBK for the group was 2,850 +/- 190 mEq. In all subjects, TBK was below that of expected (predicted from age, height, and weight). For the group this was 34 +/- 0.04% below predicted. The mean FFMDPX was 58.3 +/- 3.3 kg. Following an overnight fast, REE was measured for each subject while in a seated position. The mean REE was 1,855 +/- 70 kcal/day. REE correlates well with both TBK (r = 0.86, p < 0.0005) and FFMDPX (r = 0.80, p < 0.005). In summary, despite losses in metabolically active tissue in individuals with chronic paraplegia, TBK and FFMDPX continue to have a strong relationship with REE. REE (kcal/d) may be used as an indicator of TBK or FFMDPX using the following linear regression equations: TBK (mEq) = 2.28.REE (kcal/d) - 1,377 (SEE = +/- 347) or FFMDPX (kg) = 0.038.REE (kcal/d) - 11.5 (SEE = +/- 7).(ABSTRACT TRUNCATED AT 250 WORDS)

Dual-photon and dual-energy X-ray absorptiometry for the measurement of total-body bone mineral and soft tissue composition

Dual-photon and dual-energy X-ray absorptiometry for the measurement of total-body bone mineral and soft tissue composition

Periarticular bone mineral content in rheumatoid arthritis and arthrosis of the hip. Dual photon X-ray absorptiometry in 53 cases.

The bone mineral content (BMC) was determined by dual photon X-ray absorptiometry prior to hip replacement in 22 patients with rheumatoid arthritis and 31 with arthrosis. Compared with the arthrosis patients, the rheumatoids had approximately 20 percent lower bone mineral content in the proximal femur, the lumbar spine, and in the innominate bone superior to the acetabulum.

Age, time since menopause, and body parameters as determinants of female spinal bone mass: A mathematical model

The study of mathematical models to describe bone mass behavior throughout life is a possibility for assessing the main factors of peak bone mass and bone loss. We developed a mathematical model to predict spinal bone mass behavior on a sample of 181 healthy Italian women whose lumbar bone mineral content was determined by Gd-153 dual photon absorptiometry. This model proved to be both efficient, showing the best fit (r = 0.7 on spinal bone mineral content) when compared to other previously suggested models, and also reliable as its fit remained the best when applied to a subsequent sample of 519 women whose lumbar spine was measured by dual X-ray photon absorptiometry. This model suggests that body height and body weight (but not age) are determinants of bone mass in premenopausal women. In postmenopausal women, an accelerated phase of bone loss starting at menopause is dependent on age and time since menopause, whereas body mass index acts as a protective factor. This model confirms the influence on spinal bone mass not only of age and time since menopause but also of body size parameters.

X-ray dual-photon absorptiometry: a new method for the measurement of bone density.

A recently introduced method (dual-photon X-ray absorptiometry, DEXA) capable of measuring skeletal density in man (at present in the spine and hips, but ultimately for the whole body) has been evaluated in terms of its ability to perform long-term assessment of bone density changes. The method, which uses X rays rather than gamma rays as its photon source, represents a significant improvement over present systems both in image quality and precision (reproducibility) of results, which is better than 1% in vivo. Scanning time is approximately halved compared with present techniques and the radiation dose is reduced by 25%. First data on long-term drift of results and effects of changes in patient composition (i.e. thickness and fat content) are given and show the new method to be superior to present radionuclide systems. It is likely that this new method will become the standard for bone density measurements.

Reliability of Singh's index Checked by the Dual Photon X-ray Absorptiometry(LUNAR D.P.X)

Reliability of Singh's index Checked by the Dual Photon X-ray Absorptiometry(LUNAR D.P.X)