Sarcopenia in older people

Under-nutrition and weight loss in older people remain poorly recognized and so are undermanaged. Those at nutritional risk, and especially those losing weight, experience a loss of muscle mass referred to as sarcopenia, which is related to many different adverse health outcomes, including falls and increased risk of fracture. Although research into the condition has gained momentum over the last two decades, especially for those aged eighty years and older, research has predominately been conducted overseas. In Australia, very few studies have investigated the prevalence of sarcopenia in our older population. Local evidence is required in order to inform Australian policy makers and the health and aged care sector. Furthermore, in spite of the increasing call for appreciation, screening and early diagnosis of the condition, there is no consensus as to a preferred screening method. Without acceptable clinical screening tools, identification of sarcopenia continues to be problematic. It is therefore important to develop a simple clinical test to facilitate early detection in primary or aged care settings as part of continuing and increasing Australian research into sarcopenia. Additionally, whilst appetite loss is known to be a contributing factor, the relationship between inflammation and appetite loss in healthy individuals with no recent history of weight loss is unclear. The aims of this thesis were therefore: (1) to identify the prevalence of sarcopenia in primary care; (2) to develop and validate simple anthropometric prediction equations (PE) for lean body mass (LBM) and appendicular skeletal muscle mass (ASM); (3) to determine the performance of the ASM PE compared to dual absorptiometry x-ray assessment (DXA) of ASM in combination with grip strength; and (4) to explore the association between cytokines and appetite in a healthy population. Research from this doctoral thesis has confirmed that sarcopenia is common in community dwelling older Australians and increases with age. Anthropometric prediction equations for LBM and ASM were developed and validated: LBM= 22.932326 + 0.684668 (weight) - 1.137156 (BMI) -0.009213 (age) + 9.940015 (if male) and ASM= 10.047427 + 0.353307 (weight) - 0.621112 (BMI) - 0.022741 (age) + 5.096201 (if male). Cut-offs for low muscle mass for use in Australia was also developed. The use of ASM PE for the identification of low muscle mass, in combination with a measure of low muscle function, such as grip strength, performs well as a ‘rule out’ screening test for sarcopenia when compared to the diagnostic test of ASM assessed using DXA in combination with low grip strength. At the same time, appetite was found to be negatively associated with serum levels of pro-inflammatory IL-1ß and positively associated with serum levels of anti-inflammatory cytokine IL-10 in apparently healthy people with no recent weight loss. Research from this doctoral thesis has contributed to increased awareness that sarcopenia is common and this will aid early intervention. At the same time, a clinical screening tool to support the early diagnosis of sarcopenia was developed.Thesis (Ph.D.) (Research by Publication) -- University of Adelaide, School of Medicine, 2014