In vivo methods used to study human body composition continue to be developed, along with more advanced reference models that utilize the information obtained with these technologies. Some methods are well established, with a strong physiological basis for their measurement, whereas others are much more indirect. This review has been structured from the methodological point of view to help the reader understand what can be examined with each technique. The associations between the various in vivo methods (densitometry, dilution, bioelectrical impedance and conductance, whole body counting, neutron activation, X-ray absorptiometry, computer tomography, and magnetic resonance imaging) and the five-level multicompartment model of body composition are described, along with the limitations and advantages of each method. This review also provides an overview of the present status of this field of research in human biology, including examples of reference body composition data for infants, children, adolescents, and adults.

http://www.luzimarteixeira.com.br/wp-content/uploads/2009/09/composicao-corporal1.pdf

Human body composition: in vivo methods

Objective

To examine the bone mineral density (BMD), frequency of osteoporosis, and risk factors for BMD reduction in a representative population of female rheumatoid arthritis (RA) patients ages 20–70 years.



Methods

BMD in the femoral neck, total hip, and spine L2–4 (anterior-posterior view) was measured in 394 RA patients recruited from a validated county RA register (completeness 85%) comprising 721 women ages 20–70 years. BMD was measured with dual-energy x-ray absorptiometry, and age-specific values were compared with pooled values from a European/US population of healthy subjects free from earlier fractures, chronic diseases, and medications influencing bone metabolism. A multiple linear regression model was used to determine individual predictors of BMD.



Results

No statistically significant differences were found in demographic, disease activity, disease severity, or health status parameters between the RA register patients in whom BMD was measured and the remaining register patients. Femoral neck BMD was significantly reduced by 4.2% in the age group 50–59 years, and by 5.0% in those ages 60–70 years. For BMD in the total hip, the significant reductions were 3.7%, 6.0%, and 8.5% in the age groups 40–49 years, 50–59 years, and 60–70 years, respectively. No significant reduction in spine L2–4 BMD was found. A 2-fold increased frequency of osteoporosis was observed in all 4 age groups of RA patients compared with the reference population, ranging from 0% to 28.6% in the femoral neck, 0% to 29.9% in the total hip, and 1.8% to 31.5% in the spine. Predictors of reduced BMD were as follows: at the femoral neck, older age, low body weight, current use of corticosteroids, greater physical disability (as measured by the modified Health Assessment Questionnaire [M-HAQ]), and presence of rheumatoid factor; at the total hip, older age, low weight, current use of corticosteroids, and higher M-HAQ disability score; and at the lumbar spine, older age, low weight, and current use of corticosteroids.



Conclusion

Register-based prevalence data on BMD reduction in female RA patients ages 20–70 years are presented for the first time in this report, which demonstrates a 2-fold increase in osteoporosis in this representative population.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/1529-0131%28200003%2943%3A3%3C522%3A%3AAID-ANR7%3E3.0.CO%3B2-Y

Bone mineral density and frequency of osteoporosis in female patients with rheumatoid arthritis: results from 394 patients in the Oslo County Rheumatoid Arthritis register.

https://www.thelancet.com/pdfs/journals/lancet/PIIS0140673600021383.pdf

Inhaled corticosteroid use and bone-mineral density in patients with asthma

been published. Instruments developed to assess clinical risk factors for low bone density or fractures have moderate to high sensitivity and low specificity. Among different bone density tests measured at various sites, bone density measured at the femoral neck by dual-energy x-ray absorptiometry is the best predictor of hip fracture. Women with low bone density have approximately a 40% to 50% reduction in fracture risk when treated with bisphosphonates. Conclusions: Population screening would be based on evidence that the risk for osteoporosis and fractures increases with age, that the short-term risk for fracture can be estimated by bone density tests and risk factors, and that fracture risk can be reduced with treatment. The role of risk factor assessment and different bone density techniques, frequency of screening, and identification of subgroups for which screening is most effective remain unclear. Ann Intern Med. 2002;137:529-541. www.annals.org For author affiliations, see end of text. See related article on pp 526-528.

Screening for Postmenopausal Osteoporosis: A Review of the Evidence for the U.S. Preventive Services Task Force

We estimated peak bone mass (PBM) in 615 women and 527 men aged 16 to 40 years using longitudinal data from the Canadian Multicentre Osteoporosis Study (CaMos). Individual rates of change were averaged to find the mean rate of change for each baseline age. The age range for PBM was defined as the period during which bone mineral density (BMD) was stable. PBM was estimated via hierarchical models, weighted according to 2006 Canadian Census data. Lumbar spine PBM (1.046 ± 0.123 g/cm2) occurred at ages 33 to 40 years in women and at 19 to 33 years in men (1.066 ± 0.129 g/cm2). Total hip PBM (0.981 ± 0.122 g/cm2) occurred at ages 16 to 19 years in women and 19 to 21 years in men (1.093 ± 0.169 g/cm2). Analysis of Canadian geographic variation revealed that the levels of PBM and of mean BMD in those over age 65 sometimes were discordant, suggesting that PBM and subsequent rates of bone loss may be subject to different genetic and/or environmental influences. Based on our longitudinally estimated PBM values, the estimated Canadian prevalences of osteoporosis (T-score < –2.5) were 12.0% (L1–L4) and 9.1% (total hip) in women aged 50 years and older and 2.9% (L1–L4) and 0.9% (total hip) in men aged 50 years and older. These were higher than prevalences using cross-sectional PBM data. In summary, we found that the age at which PBM is achieved varies by sex and skeletal site, and different reference values for PBM lead to different estimates of the prevalence of osteoporosis. Furthermore, lack of concordance of PBM and BMD over age 65 suggests different determinants of PBM and subsequent bone loss. © 2010 American Society for Bone and Mineral Research

/pdf/peak-bone-mass-from-longitudinal-data-implications-for-the-4wbrzyz9po.pdf

Peak bone mass from longitudinal data: Implications for the prevalence, pathophysiology, and diagnosis of osteoporosis

The construction of reference ranges that accurately represent the population at large is essential for the correct identification of osteoporosis from bone mineral density (BMD) measurements. In this study, reference data supplied by the manufacturer of the Lunar DPX+ bone densitometer were compared with data obtained locally. Lumbar spine, proximal femur and total body BMD measurements were made in an age-stratified random sample of 702 Southampton women aged 20 to 89 years. Relevant demographic and medical data were recorded for each subject using a questionnaire. Reference curves of BMD (mean +/- SD) were plotted against age for each measurement site and were found to be higher than the manufacturer's reference values at all ages and sites. Exclusion of women with factors known to affect bone mass only served to increase this discrepancy. According to World Health Organisation definitions, osteoporosis may be identified from BMD values alone. Based upon neck of femur BMD values, 100 (14.8%) of the women in this study group were categorized as osteoporotic using local young normal reference data, compared with only 39 (5.8%) using the manufacturer's data. By normalizing for age distribution, these findings were extrapolated to the local population where it was predicted that 26.0% and 10.1% of females over 50 years of age would be classified as osteoporotic using the respective reference ranges. This study clearly illustrates how the numbers of women diagnosed as osteoporotic vary with the use of different reference populations.

Reference ranges of bone mineral density for women in southern England: the impact of local data on the diagnosis of osteoporosis.

Fundamental differences in axial and appendicular bone density in stress fractured and uninjured Royal Marine recruits--a matched case-control study.

Selective reduction in trabecular volumetric bone mineral density during treatment for childhood acute lymphoblastic leukemia

We studied a prospective UK cohort of women aged 20 to 80 years, assessed by dual-energy X-ray absorptiometry (DXA) at baseline. Bone mineral content (BMC) and areal bone mineral density (aBMD), but not bone area (BA), at femoral neck, lumbar spine and the whole body sites were similarly predictive of incident fractures. Low aBMD, measured by DXA, is a well-established risk factor for future fracture, but little is known about the performance characteristics of other DXA measures such as BA and BMC in fracture prediction. We therefore investigated the predictive value of BA, BMC and aBMD for incident fracture in a prospective cohort of UK women. In this study, 674 women aged 20–80 years, recruited from four GP practices in Southampton, underwent DXA assessment (proximal femur, lumbar spine, total body) between 1991 and 1993. All women were contacted in 1998–1999 with a validated postal questionnaire to collect information on incident fractures and potential confounding factors including medication use. Four hundred forty-three women responded, and all fractures were confirmed by the assessment of images and radiology reports by a research nurse. Cox proportional hazard models were used to explore the risk of incident fracture, and the results are expressed as hazard ratio (HR) per 1 SD decrease in the predictor and 95% CI. Associations were adjusted for age, BMI, alcohol consumption, smoking, HRT, medications and history of fracture. Fifty-five women (12%) reported a fracture. In fully adjusted models, femoral neck BMC and aBMD were similarly predictive of incident fracture. Femoral neck BMC: HR/SD = 1.64 (95%CI: 1.19, 2.26; p = 0.002); femoral neck aBMD: HR/SD = 1.76 (95%CI: 1.19, 2.60; p = 0.005). In contrast, femoral neck BA was not associated with incident fracture, HR/SD = 1.15 (95%CI: 0.88, 1.50; p = 0.32). Similar results were found with bone indices at the lumbar spine and the whole body. In conclusion, BMC and aBMD appear to predict incident fracture with similar HR/SD, even after adjustment for body size. In contrast, BA only weakly predicted the future fracture. These findings support the use of DXA aBMD in fracture risk assessment, but also suggest that factors which specifically influence BMC will have a relevance to the risk of the incident fracture.

/pdf/bone-mineral-content-and-areal-density-but-not-bone-area-3s634qezrs.pdf

P A Taylor

Papers

Reference ranges of bone mineral density for women in southern England: the impact of local data on the diagnosis of osteoporosis.

Fundamental differences in axial and appendicular bone density in stress fractured and uninjured Royal Marine recruits--a matched case-control study.

Selective reduction in trabecular volumetric bone mineral density during treatment for childhood acute lymphoblastic leukemia

Bone mineral content and areal density, but not bone area, predict an incident fracture risk: a comparative study in a UK prospective cohort.

Dxa measures of bone mass in mother, father and offspring: results from the southampton women's survey