- Title
- Addressing sarcopenia in an aging population
- Creator
- Stoodley, Isobel Louise
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2022
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- The Australian population is aging; one in six Australians are currently aged 65 years and older (1). A key disease of aging is sarcopenia, the age-related loss of muscle mass, strength and/or physical function (2). Sarcopenia can be caused by sedentary lifestyle (3), poor nutritional intake and malabsorption (3), an increase in low-grade chronic inflammation (4, 5), and it increases the risk of falls (6, 7), hospitalisation (8-11), loss of independence and quality of life (12-15), and mortality (10, 16-20). Due to the significant disability associated with sarcopenia, it is imperative to find effective prevention and treatment strategies. While lifestyle interventions are the mainstay of prevention and treatment options for sarcopenia, research investigating the optimal prescription of both protein and resistance training (RT) is required in order to decrease the years affected by sarcopenia as well as age-related disability. Therefore, this thesis aims to: examine the existing evidence for protein and exercise interventions to improve body composition, strength and physical function in older adults; investigate the optimal components of these interventions; investigate utilising protein and physical activity cut-points as determinants of sarcopenia risk; examine the effect of a 16-week high- versus low-dose protein intervention in combination with RT in these high-risk older adults on body composition, strength and physical function measures; and lastly to determine the long-term (12 month) benefits of participating in a short-course combined protein and RT intervention on these measurements. Chapter 2 presented the current evidence for combined protein and exercise interventions compared to exercise-only interventions on measurements relevant to sarcopenia prevention. This systematic review and meta-analysis revealed that for knee extension strength, there appeared to be a beneficial effect of the addition of protein; however, there was limited evidence for the effect of protein on other outcomes such as body composition, grip strength, biomarkers, and quality of life. However, when investigating components of protein interventions, timing of protein appeared important, with supplementation at meals beneficial for muscle mass accretion, and between meal supplementation beneficial for knee extension strength. While overall protein dose did not influence outcomes, few studies assessed baseline dietary intakes (despite assessing baseline physical activity levels), and this would be important for future studies to address. Lastly, most of the included studies used milk proteins as the source of protein, with few studies using plant-based protein sources. Future research should investigate diversified protein types to determine their effectiveness in older adults. Chapter 4 assessed the ability of protein and physical activity cut-points to determine sarcopenia risk. Older adults with low usual protein intake (≤1g∙kg-1∙day-1) and low physical activity levels (≤150 min∙week-1) (high risk) were compared to older adults with moderate-high protein intake (>1g∙kg-1∙day-1) who met recommended physical activity levels (>150 min∙week-1) (low risk). High-risk individuals had lower percentage muscle mass, higher fat mass, poorer upper and lower limb strength and physical function outcomes, and poorer quality of life, compared to low risk individuals. These associations were sex-dependent, with greater differences between high and low-risk females. Furthermore, 19% of the high-risk individuals met the European Working Group for Sarcopenia in Older People (EWGSOP) functional criteria for sarcopenia compared to none in the low-risk group. As the functional criteria are only applied after meeting strength and muscle requirements, the current definition of sarcopenia does not identify individuals with impaired function who may benefit from early intervention. Future research into protein and physical activity cut-points are needed to confirm these findings and establish clear pre-sarcopenia definitions. Chapter 5 presented the effect of a high- versus low-dose protein intervention, combined with RT, in older adults at high-risk of developing sarcopenia. High-risk older adults were randomised to either a high-dose protein drink (plant-based protein powder + 250mL cow’s milk, consumed twice per day at breakfast and dinner, ~46g protein∙day-1) or a low-dose protein drink (250mL cow’s milk, twice per day at breakfast and dinner, ~19g protein∙day-1), in combination with a 16 week progressive, home-based RT program (four sessions∙week-1). Interestingly, both groups showed similar improvements in muscle mass, strength, and physical function. However, both groups increased their protein intake to ≥1 g∙kg-1∙day-1. In older adults with poor protein intake, increasing to ≥1 g∙kg-1∙day-1 appears to be a suitable target in combination with RT. However, future research is needed to verify whether plant-based protein alone can impart similar benefits to combined plant- and animal-based protein sources. Lastly, Chapter 6 presented the 12-month follow-up of participants who had completed the short course, 16 week combined protein and exercise intervention. At 12-month follow-up, participants retained some strength benefits, despite declines in muscle mass. Gait speed decreased below baseline levels, however, functional measures such as the Short Physical Performance Battery score remained higher at 12 months. Exercise time was positively correlated with increased muscle mass and shoulder adduction strength, indicating that exercise maintenance may have additional benefits. However, there were still benefits maintained from the short course intervention at 12 months, which could provide an alternative prescription strategy for older adults and sarcopenia prevention. Future research should directly compare short-term (12-16 week) interventions against longer-term interventions (≥12 months) at identical timepoints to investigate if long-term engagement with RT and protein interventions results in greater benefits in body composition, strength, and function. Overall, the research conducted as part of this thesis has contributed to the evidence for sarcopenia prevention in older adults. In particular, this thesis has clarified optimal protein and exercise components to improve muscle mass, strength, and function in older adults; expanded understanding of risk factors for sarcopenia; defined alternative definitions for pre-sarcopenia; provided evidence for combined protein and RT interventions to improve muscle mass, strength, and function in high-risk individuals; and provided evidence for long-term benefits of these short-course combined interventions. The research from this thesis has successfully identified individuals at high risk of developing sarcopenia, reduced their risk using a short lifestyle intervention, and showed that some of these benefits can be maintained long-term. This thesis has progressed health aging research in Australia and created new avenues to address sarcopenia in an aging population.
- Subject
- aging; nutrition; physical activity; resistance training; protein; sarcopenia
- Identifier
- http://hdl.handle.net/1959.13/1504776
- Identifier
- uon:55572
- Rights
- Copyright 2022 Isobel Louise Stoodley
- Language
- eng
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