Zainol Abidin, Nurdiana
(2021)
Osteosarcopenic obesity: the development of screening test criteria and the association with bioavailable 25(OH)D.
PhD thesis, University of Nottingham.
Abstract
Concurrent presence of low bone density (osteopenia/osteoporosis), low muscle mass (sarcopenia), and high adiposity (obesity) in the elderly has led to the recognition of Osteosarcopenic Obesity (OSO) as a singular entity. Currently, no established criteria exist to identify OSO, particularly in Malaysian population. Therefore, the main aim of this study was to develop simple screening test to identify obese Malaysian postmenopausal women at high risk for osteosarcopenia using portable equipment; quantitative ultrasound (QUS) and bio-electrical impedance analysis (BIA). Additionally, the relationships between OSO and 25(OH)D indices were also explored. One-hundred and forty-one (n=141) functionally independent, community-dwelling postmenopausal Malaysian women (aged 45 to 88 years) were recruited from the area of Klang Valley, Kuala Lumpur, Malaysia. Body composition was assessed using BIA and bone density was assessed using QUS. Serum total 25(OH)D was measured using chemiluminescent microparticle immunoassay (CMIA). Serum vitamin D binding protein (VDBP) was measured using a monoclonal enzyme-linked immunosorbent assay (ELISA) and bioavailable 25(OH)D was calculated using modified Vermuelen formula. After selecting the best variables using receiver operating characteristic (ROC) curve, the final model to estimate the risk of osteosarcopenia in obese women comprised of five variables: handgrip strength (HGS, ≤16.5kg), skeletal muscle mass index (SMMI, ≤8.2 kg/m2), fat-free mass index (FFMI, ≤15.2kg/m2), broadband ultrasonic attenuation (BUA, ≤52.85 dB/MHz) and speed of sound (SOS, ≤1492.15 m/s). Mean and SD of total, bioavailable 25(OH)D, and VDBP was, 52.4(17.7) nmol/L, 6.9(3.0) nmol/L, and 224.7(44.8) ug/mL, respectively. A significant and positive correlation was found between total 25(OH)D and bioavailable 25(OH)D (r=0.883, p<0.01). Both total and bioavailable 25(OH)D were negatively correlated with body fat percent and positively correlated with muscle mass (p<0.05). Although both forms of 25(OH)D were positively correlated with bone density (BUA), the correlation of bioavailable 25(OH)D was marginally stronger compared to total 25(OH)D (r=0.234, p=0.012 and r=0.199, p=0.030, respectively). However, the small differences in the R values and effect size does not warrant the conclusion that bioavailable 25(OH)D is superior to total 25(OH)D in its association with the BUA. While no significant correlation was found between OSO and any index of 25(OH)D, participants with severe obesity [Body fat %: Mean (SD) 44.9 (4.7) %] and concurrent presence of low bone density (Osteopenic Obesity) were likely to be Vitamin D deficient (total 25(OH)D <30nmol/L) compared to participants without any musculoskeletal health disorders, obese or otherwise (p=0.070). OSO is a progressive disorder that could lead to functional impairment. The screening test developed from this study could help identify asymptomatic obese women with osteosarcopenia who may be good candidates for early intervention. Severely obese people are prone to hypovitaminosis D, which could lead to the manifestation of musculoskeletal health disorders. Intervention measures should include an effort to increase Vitamin D levels.
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