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Local adipose tissue impairs cortical bone quality, microstructure in older women
Adipose tissue depots at cortical bone sites are inversely associated with bone material strength index and cortical bone microstructure, according to research in the Journal of Bone and Mineral Research.
In a cross-sectional, population-based study of older Swedish women, researchers also found that women in the highest quartile of tibial subcutaneous fat had both a lower bone material strength index (BMSi) and higher cortical porosity than women in the lowest quartile.
“We speculate that a possible direct negative influence of local adipose tissue on cortical BMSi, density and porosity could be a contributing factor as to why overweight patients are more prone to fractures in extremities ... such as the upper arm or ankle,” Daniel Sundh, a PhD student at the Institute of Medicine at University of Gothenburg, Sweden, and colleagues wrote. “However, it should be acknowledged that increased weight in obesity induces higher loads affecting the bone of the ankle to greater repeated stresses over time, which could also contribute to the increased fracture risk at this site.”
Sundh and colleagues analyzed data from 202 postmenopausal women aged 75 to 80 years (mean age, 78 years; mean weight, 69.2 kg; mean height, 161.2 cm; mean calcium intake, 751 mg per day) who agreed to bone material strength testing. Researchers measured volumetric bone mineral density, cortical bone microstructure, cortical pore volume, cortical bone volume, cortical volumetric BMD, cortical thickness, cortical area and total area and subcutaneous fat at the distal tibia via high-resolution peripheral quantitative CT (HR-pQCT). Researchers measured BMSi at the tibia using the OsteoProbe (Active Life Scientific) for microindentation. DXA was used to measure body composition. Researchers used bivariate correlations to analyze the association between bone geometry, microstructure, body composition and BMSi.
Participants self-reported calcium intake, medical history, medication use, smoking history and fracture history going back to age 50 years via questionnaires.
Researchers found that BMSi was negatively associated with BMI (r = –0.17; P = .01), whole-body fat mass (r = –0.16; P = .02), and tibia subcutaneous fat (r = –0.33; P < .001). Tibia subcutaneous fat also was correlated to cortical porosity (r = 0.19; P = .01) and cortical volumetric BMD (r = –0.23; P = .001).
Tibia subcutaneous fat was associated with BMSi (beta level = –0.34; P < .001), cortical porosity (beta level = 0.18; P = .01), and cortical volumetric BMD (beta level = –0.32; P < .001) independently of covariates in linear regression analysis.
“BMSi was independent of covariates associated with cortical porosity ([beta level] = –0.14; P = .04) and cortical volumetric BMD ([beta level] = 0.21; P = .02) at the distal tibia, but these bone parameters could only explain 3.3% and 5.1% of the variation in BMSi, respectively,” the researchers wrote.
Researchers also found that tibial subcutaneous fat was not significantly associated with fracture prevalence in the lower extremities after adjustment (OR = 0.85; 95% CI, 0.51-1.41). – by Regina Schaffer
Disclosure: The researchers report no relevant financial disclosures.