Adiposity and bone microarchitecture in the GLOW study

Association between obesity and the prevalence of fractures: a population-based cross-sectional study in China

Although obesity is generally associated with increased bone mass, recent data have challenged its potential protective effect. Our study found that increased BMI showed beneficial effects on BMD in a non-linear way. However, individuals with obesity, especially women, were more likely to have vertebral fractures. There was a U-shaped relationship between BMI and the prevalent fractures.

PURPOSE

To estimate the association of obesity with the prevalence of fractures in the Mainland Chinese population.

METHODS

A total of 8251 individuals from the COPS cohort were enrolled in this cross-sectional study and grouped by BMI level. The Five-Repetition Sit-to-Stand Test (5R-STS) and the Sharpened Romberg test were used to evaluate the balance ability. Vertebral fractures (VFs) were confirmed by spine X-ray examination. Prevalent fractures were defined by a self-report questionnaire which happened in the recent 5 years. The restricted cubic spline (RCS) was used to explore the non-linear relationship. Multiple linear regression and multivariable logistic regression were conducted to adjust the covariates.

RESULTS

Obesity was correlated with a reduced bone turnover rate and increased BMD. Nevertheless, there were significant non-linear correlations between BMI and BMD, with a rapid increase and plateau at extremely high BMI levels (p for non-linear < 0.001 for all). Individuals with obesity were associated with a longer time of the 5R-STS and more likely to have a positive Sharpened Romberg test, especially in women. Compared with the normal weight group, the likelihood of prevalence of VFs and the prevalent fractures were significantly increased in the obesity group, independent of the Sharpened Romberg test and lumbar spine BMD (VFs: OR = 1.88 [95% CI 1.38-2.56]; prevalent fractures: OR = 2.18 [95% CI 1.39-3.41]). Per standard deviations (SD) increase in BMI was associated with 21% and 22% increase in the prevalence of VFs and prevalent fractures, respectively. Moreover, the prevalence of prevalent fractures also elevated in the low-weight individuals (OR = 2.62 [95% CI 1.34-4.75]), which indicated a U-shaped relationship between BMI and the prevalence of prevalent fractures.

CONCLUSION

Obesity was associated with higher BMD in a non-linear manner. However, BMI was positively associated with the prevalence of VFs, and there was a U-shaped relationship between BMI and the prevalent fractures.

Correlation between Body Composition and Bone Mineral Density Differs by Sex and Skeletal Site in Overweight and Obese Chinese Subjects

Previous studies have yielded inconsistent results regarding the relationship between obesity and bone mineral density (BMD). The aim of this study was to determine the influence of body composition on BMD and the serum sclerostin level in overweight and obese adults. The study had a cross-sectional design and included 90 men and 118 women with a body mass index ≥25. Fat mass, lean mass, and spinal and pelvic BMD were measured using dual-emission X-ray absorptiometry. Subcutaneous fat, visceral fat, and lean mass were measured between L2 and L3 by 16-slice spiral computed tomography. The serum sclerostin level was determined by enzyme-linked immunosorbent assay. Pearson analysis showed that fat mass and appendicular lean mass were positively correlated with spinal BMD in both sexes. A positive association of both fat mass and lean mass with pelvic BMD, which was stronger in women, was also found. Partial correlation analysis showed the positive association between fat mass and BMD was significantly attenuated but the positive association between lean mass and pelvic BMD remained after adjustment for age and body weight. A negative correlation was observed between visceral fat and spinal and pelvic BMD only in women, and the positive association between lean mass with pelvic BMD was more obvious in women than in men, indicating body composition seemed to have a greater impact on the BMD in women. The serum sclerostin level was positively associated with BMD but not with body composition. These findings suggest that the correlation between body composition and BMD is influenced by sex and skeletal site.

Causal relationships between height and weight with distal tibia microarchitecture and geometry in adult female twin pairs

Higher stature and lower weight are associated with increased risk of fracture. However, the pathophysiology for the associations of height and weight with bone microarchitecture and geometry is unclear. We examined whether these associations were consistent with causation and/or with shared familial factors. In this cross-sectional study of 566 female twins aged 26-76 yr, a regression analysis for twin data, Inference about Causation by Examination of FAmilial CONfounding (ICE FALCON), was used for testing causation. The bone microarchitecture and geometry of the distal tibia was assessed using HR-pQCT and the StrAx1.0 software. Higher stature was associated with larger total bone cross-sectional area (CSA), lower total bone volumetric bone mineral density (vBMD), larger cortical CSA, thinner cortices, higher porosity of the total cortex, compact cortex, outer and inner transitional zone (TZ), lower cortical vBMD, and larger medullary CSA (regression coefficients (β) ranging from -.37 to .60, all p<.05). Using ICE FALCON, the cross-pair cross-trait associations attenuated toward zero after adjusting for the within-individual association (absolute values of β ranging from .05 to .31, all p<.001). Higher weight was associated with higher total bone vBMD, larger cortical CSA and thicker cortices, lower porosity of the total cortex and inner TZ, and higher cortical vBMD (β ranging from -.23 to .34, all p<.001), and thinner trabeculae, higher trabecular number, lower trabecular separation, and higher trabecular vBMD (β ranging from -.31 to .39, all p<.05). Only cortical CSA attenuated toward zero after adjusting for the within-individual association between weight and bone microarchitecture (β = .042, p=.046). Higher stature was associated with a weaker cortical, not trabecular bone traits, whereas higher weight was associated with stronger cortical and trabecular bone traits. The results were consistent with height having a causal effect on weaker cortical bone structure, whereas weight had a casual effect on the larger cortical CSA.

Effect of BMI-Discordant Abdominal Tissue Thickness on Fracture Probability: A Registry-Based Study

FRAX, which is used to assess fracture probability, considers body mass index (BMI), but BMI may not reflect individual variation in body composition and distribution. We examined the effect of BMI-discordant abdominal thickness on FRAX-derived fracture probability for major osteoporotic fracture (MOF) and hip fracture. We studied 73,105 individuals, mean age 64.2 years. During mean 8.7 years, 7048 (9.6%) individuals sustained incident MOF, including 2155 (3.0%) hip fractures. We defined abdominal thickness index (ATI) as the difference between abdominal thickness measured by dual-energy X-ray absorptiometry (DXA) and thickness predicted by BMI using sex-stratified regression. ATI was categorized from lower (<-2 cm, -2 to -1 cm) to higher (1-2 cm, >+2 cm) with referent around zero (-1 to +1 cm). Adjusted for FRAX probability, increasing ATI was associated with incident MOF and hip fracture (p < 0.001). For the highest ATI category, MOF risk was increased (hazard ratio [HR] = 1.23, 95% confidence interval [CI] 1.12-1.35) independent of FRAX probability. Similar findings were noted for hip fracture probability (HR = 1.28, 95% CI 1.09-1.51). There was significant age-interaction with much larger effects before age 65 years (HR = 1.44, 95% CI 1.23-1.69 for MOF; 2.29, 95% CI 1.65-3.18 for hip fracture). In contrast, for the subset of individuals with diabetes, there was also increased risk for those in the lowest ATI category (HR = 1.73, 95% CI 1.12-2.65 for MOF; 2.81, 95% CI 1.59-4.97 for hip fracture). Calibration plots across ATI categories demonstrated deviation from the line of identity in women (calibration slope 2.26 for MOF, 2.83 for hip fracture). An effect of ATI was not found in men, but this was inconclusive as the sex-interaction terms did not show significant effect modification. In conclusion, these data support the need to investigate increased abdominal thickness beyond that predicted by BMI and sex as a FRAX-independent risk factor for fracture. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

High-resolution peripheral quantitative computed tomography: research or clinical practice?

High-resolution peripheral quantitative CT (HR-pQCT) is a low-dose three-dimensional imaging technique, originally developed for in vivo assessment of bone microarchitecture at the distal radius and tibia in osteoporosis. HR-pQCT has the ability to discriminate trabecular and cortical bone compartments, providing densitometric and structural parameters. At present, HR-pQCT is mostly used in research settings, despite evidence showing that it may be a valuable tool in osteoporosis and other diseases. This review summarizes the main applications of HR-pQCT and addresses the limitations that currently prevent its integration into routine clinical practice. In particular, the focus is on the use of HR-pQCT in primary and secondary osteoporosis, chronic kidney disease (CKD), endocrine disorders affecting bone, and rare diseases. A section on novel potential applications of HR-pQCT is also present, including assessment of rheumatic diseases, knee osteoarthritis, distal radius/scaphoid fractures, vascular calcifications, effect of medications, and skeletal muscle. The reviewed literature seems to suggest that a more widespread implementation of HR-pQCT in clinical practice would offer notable opportunities. For instance, HR-pQCT can improve the prediction of incident fractures beyond areal bone mineral density provided by dual-energy X-ray absorptiometry. In addition, HR-pQCT may be used for the monitoring of anti-osteoporotic therapy or for the assessment of mineral and bone disorder associated with CKD. Nevertheless, several obstacles currently prevent a broader use of HR-pQCT and would need to be targeted, such as the small number of installed machines worldwide, the uncertain cost-effectiveness, the need for improved reproducibility, and the limited availability of reference normative data sets.

Muscle-to-Bone and Soft Tissue-to-Bone Ratio in Children and Adolescents with Obesity

OBJECTIVES

To explore the total and regional muscle-to-bone ratio in children and adolescents with obesity and compare the muscle-to-bone ratio (MBR) and soft tissue-to-bone ratio (SBR) to their peers with normal weight or overweight.

STUDY DESIGN

A total of 219 male and female pediatrics (mean age=12.3±2.5 years) participated in this study. Body composition was assessed with a total body dual X-ray absorptiometry. The MBR was calculated by dividing lean mass by bone mineral content. The SBR was determined by dividing the soft tissue mass (i.e., lean mass+fat mass) by bone mineral content. Differences in total and regional body composition measures between body mass index (BMI) percentile groups was assessed by ANOVA.

RESULTS

The obesity group had significantly higher MBR compared to the normal weight group for total (19.24±1.56 vs. 18.26±1.64), arm (17.11±1.67 vs. 15.88±1.81), and leg (18.41±1.68 vs. 16.62±1.55). Similarly, the obesity group had significantly higher MBR in the leg (18.41±1.68) compared to the overweight group (17.24±1.45). However, the overweight group was not significantly different from the normal weight or the obesity group for total and arm MBR. The total, arm, and leg SBR was significantly different between all BMI groups. Across the entire sample, MBR and SBR were negatively associated with high-density lipoprotein. SBR was positively associated with insulin, HOMA-IR, low-density lipoprotein, very low-density lipoprotein, triglycerides, and systolic blood pressure.

CONCLUSIONS

Children with obesity had a higher MBR and SBR compared to their normal weight peers. In addition, there were significant associations between SBR, higher levels of insulin, atherogenic lipoproteins, and increased systolic blood pressure. Thus, SBR may be useful as a marker for increased cardiometabolic disease risk, though more research in this area is warranted.

Associations between body composition, physical activity, and diet and radial bone microarchitecture in older adults: a 10-year population-based study

Bone strength is important to prevent osteoporotic fractures and determined by bone mass and microarchitecture. This study suggests that having higher lean mass and lower fat mass, avoiding western dietary patterns, and improving steps per day may all be important for maintaining bone mass and microarchitecture in aging.

PURPOSE

To describe associations between exposures of lean mass and fat mass, dietary patterns, serum 25-hydroxyvitamin D (25(OH)D), physical activity and grip strength, and bone outcome measures including bone mineral density and microarchitecture in older adults.

METHODS

Data on 201 older adults (mean age 72 years, female 46% at 10.7-year follow-up (phase 4) from a population-based cohort study collected at baseline and follow-up at 2.6 (phase 2), 5.1 (phase 3), and 10.7 years (phase 4) were analyzed. Exposures were lean and fat mass, dietary patterns, physical activity (steps per day), serum 25(OH)D concentrations, and grip strength during follow-ups. Bone measures at phase 4 including areal bone mineral density (aBMD) at the spine, hip, and whole body by dual-energy X-ray absorptiometry, and radial cortical and trabecular bone microarchitecture by high-resolution peripheral computed tomography (HRpQCT). The cumulative average values of exposures were calculated. Multivariable linear regression was used to analyze associations between exposures and bone measures.

RESULTS

Lean mass was beneficially associated with the hip, spine, and total body aBMD, radial cortical and trabecular bone area, and trabecular number and separation (β ranged from - 0.39/standard deviation (SD) to 0.73/SD). Fat mass was detrimentally associated with radial compact cortical and inner transitional zone bone area, vBMD, and porosity (β ranged from - 0.21 to 0.22/SD). Western dietary pattern scores were detrimentally associated with radial total and cortical bone vBMD and porosity (β ranged from - 0.20 to 0.20/SD). Steps per day were beneficially associated with inner transitional zone area and thickness (β = 0.12/SD and 0.19/SD), but no other measures. Grip strength and serum 25(OH)D were not associated with any radial bone measures.

CONCLUSIONS

Lean mass was beneficially associated with aBMD, radial bone area, and trabecular bone microarchitecture. Fat mass had detrimental associations with radial bone area, vBMD, and porosity. A western dietary pattern was detrimental for radial bone microarchitecture while more steps per day (but not grip strength or 25(OH)D) appeared beneficial.

Bone Microarchitecture in Obese Postmenopausal Chinese Women: The Chinese Vertebral Osteoporosis Study (ChiVOS)

BACKGROUND

Obesity is associated with improved bone mass and microarchitecture in Caucasian individuals, but evidence in obese Asian individuals is lacking.

OBJECTIVE

To analyze the areal bone mineral density (aBMD) and bone microarchitecture in normal-weight, overweight, and obese postmenopausal Chinese women.

METHODS

A total of 243 postmenopausal women from the Chinese Vertebral Osteoporosis Study (ChiVOS) were included and were divided into three groups (OB, obese group; OW, overweight group; NW, normal weight group) by BMI level. aBMD, trabecular bone score (TBS), and appendicular lean mass (ALM) were measured by dual-energy X-ray absorptiometry (DXA). Bone microarchitecture was measured by HR-pQCT at the distal radius and tibia. X-ray was performed to confirm vertebral fractures (VFs). Multiple linear regression was used to evaluate the correlations between bone parameters and ALM after adjusting for confounding variables.

RESULTS

The prevalence of VFs and clinical fractures were similar among the groups. Participants in the OB group showed a lower level of osteocalcin with comparable levels of other bone turnover markers (BTMs). The aBMD at several skeletal sites was higher in the OB group than in the NW group after adjusting for age (p<0.01 for all comparisons). At the radius, the OB group had a higher Ct.Ar, Tb.vBMD, Tb.BV/TV, Tb.N, Tb.Th, and Ct.Th than the NW group after adjusting for covariates (p<0.05 for all). Differences of a similar magnitude were found at the distal tibia. There was a trend of decreasing trend in Tb.Sp, Tb.1/N/SD, and Ct.Po among groups at both sites. However, the bone microarchitecture did not differ between participants with severe obesity (BMI≥35.0kg/m²) and those with 30.0≤BMI<35 kg/m². Multiple linear regression revealed that the associations between ALM and most of the bone microarchitecture parameters at both sites were much stronger than the association between body weight and bone parameters.

CONCLUSION

We have observed significant improvements in aBMD, bone geometry, and bone microarchitecture in obese postmenopausal Chinese women. Except for a lower level of osteocalcin in the OB group, no significant differences in BTMs were found among the groups. Compared with body weight, ALM may explain greater variance in the improvement of bone microarchitecture parameters.

MRI-based Texture Analysis of Trabecular Bone for Opportunistic Screening of Skeletal Fragility

CONTEXT

Many individuals at high risk for osteoporosis and fragility fracture are never screened by traditional methods. Opportunistic use of imaging obtained for other clinical purposes is required to foster identification of these patients.

OBJECTIVE

The aim of this pilot study was to evaluate texture features as a measure of bone fragility, by comparing clinically acquired magnetic resonance imaging (MRI) scans from individuals with and without a history of fragility fracture.

METHODS

This study retrospectively investigated 100 subjects who had lumbar spine MRI performed at our institution. Cases (n = 50) were postmenopausal women with osteoporosis and a confirmed history of fragility fracture. Controls (n = 50) were age- and race-matched postmenopausal women with no known fracture history. Trabecular bone from the lumbar vertebrae was segmented to create regions of interest within which a gray level co-occurrence matrix was used to quantify the distribution and spatial organization of voxel intensity. Heterogeneity in the trabecular bone texture was assessed by several features, including contrast (variability), entropy (disorder), and angular second moment (homogeneity).

RESULTS

Texture analysis revealed that trabecular bone was more heterogeneous in fracture patients. Specifically, fracture patients had greater texture variability (+76% contrast; P = 0.005), greater disorder (+10% entropy; P = 0.005), and less homogeneity (-50% angular second moment; P = 0.005) compared with controls.

CONCLUSIONS

MRI-based textural analysis of trabecular bone discriminated between patients with known osteoporotic fractures and controls. Further investigation is required to validate this promising methodology, which could greatly expand the number of patients screened for skeletal fragility.