Melbourne Medical School Collected Works - Research Publications
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ItemOperational definitions of sarcopenia and their associations with 5-year changes in falls risk in community-dwelling middle-aged and older adults(SPRINGER LONDON LTD, 2014-01-01)UNLABELLED: Sarcopenia may be diagnosed in the clinic using operational definitions based on low muscle mass or function. This prospective, population-based study revealed that sex-specific associations may exist between operational definitions of sarcopenia and falls in community-dwelling middle-aged and older adults. INTRODUCTION: The objective of this study is to verify associations between sarcopenia and falls risk and to determine changes in sarcopenia prevalence over 5 years in middle-aged and older men and women according to different anthropometric and performance-based operational definitions. METHODS: N = 681 volunteers (48% female; mean ± SD age 61.4 ± 7.0 years) participated in baseline and follow-up assessments (mean 5.1 ± 0.5 years later). Appendicular lean mass (ALM) was assessed by dual-energy X-ray absorptiometry, hand grip (HGS) and lower-limb (LLS) strength were assessed by dynamometry, and falls risk was determined using the physiological profile assessment. Anthropometric definitions (ALM/height squared [ALM-H], ALM/weight × 100 and a residuals method [ALM-R]) and performance-based definitions (HGS, LLS and upper- and lower-limb muscle quality [LMQ]) of sarcopenia were examined. The lowest 20% of the sex-specific distribution for each definition at baseline was classified as sarcopenia. RESULTS: Sarcopenia prevalence increased after 5 years for all operational definitions except ALM-H (men: -4.0%; women: -5.5%). Men classified with sarcopenia according to anthropometric definitions, and women classified with sarcopenia according to performance-based definitions, had significant increases in falls risk over 5 years (all P < 0.05) compared to individuals without sarcopenia. Significant sex interactions were observed for ALM-R, LLS and LMQ (all P < 0.05) definitions. CONCLUSIONS: Sarcopenia prevalence generally increases at a higher rate when assessed using performance-based definitions. Sarcopenia is associated with increases in falls risk over 5 years in community-dwelling middle-aged and older adults, but sex-specific differences may exist according to different anthropometric or performance-based definitions.
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ItemCalf muscle density is independently associated with physical function in overweight and obese older adults(JMNI, 2018-03-01)OBJECTIVES: To determine whether associations of calf muscle density with physical function are independent of other determinants of functional decline in overweight and obese older adults. METHODS: This was a secondary analysis of a cross-sectional study of 85 community-dwelling overweight and obese adults (mean±SD age 62.8±7.9 years; BMI 32.3±6.1 kg/m2; 58% women). Peripheral quantitative computed tomography assessed mid-calf muscle density (66% tibial length) and dual-energy X-ray absorptiometry determined visceral fat area. Fasting glucose, Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) and C-reactive protein (CRP) were analysed. Physical function assessments included hand grip and knee extension strength, balance path length (computerised posturography), stair climb test, Short Physical Performance Battery (SPPB) and self-reported falls efficacy (Modified Falls Efficacy Scale; M-FES). RESULTS: Visceral fat area, not muscle density, was independently associated with CRP and fasting glucose (B=0.025; 95% CI 0.009-0.042 and B=0.009; 0.001-0.017, respectively). Nevertheless, higher muscle density was independently associated with lower path length and stair climb time, and higher SPPB and M-FES scores (all P⟨0.05). Visceral fat area, fasting glucose and CRP did not mediate these associations. CONCLUSIONS: Higher calf muscle density predicts better physical function in overweight and obese older adults independent of insulin resistance, visceral adiposity or inflammation.