What is sarcopenia?
Sarcopenia can be described as a loss of skeletal muscle mass, muscle function and strength that occurs with aging. Sarcopenia can significantly impact on quality of life and lead to other chronic disease states. Lack of a clinical definition of sarcopenia means that its prevalence in Australia is difficult to determine. However, it is estimated that up to 29% of the community-dwelling population and up to 33% of those in long term care are affected (1). Whilst sarcopenia is often associated with the elderly in aged care, those requiring assistance and frailty, the reality is that muscle decline and sarcopenia begin much earlier in life and often goes unnoticed.
How does sarcopenia progress and who is at risk?
Age is the major determining risk factor for sarcopenia; muscle mass can begin to decline by the 4th decade of life and by the 8th decade total muscle may have declined by up to a 50%. Genetics, lifestyle and the presence of other chronic disease are also contributing factors to loss of muscle mass (2, 3).
As we age the number of muscle fibres, most notably the type 2 fast twitch muscle fibres, begin to decline. Additionally, the precursor or satellite cells – which are activated to repair and build muscle after weight bearing exercise or trauma – also begin to reduce in concentration. These physiological changes make the muscle building and repair process less effective and together with a decline in physical activity and nutritional status contributes to the progression of sarcopenia (2).
When overweight or obesity is present sarcopenia may not be as noticeable, yet it is equally as detrimental to health. This is referred to as sarcopenic obesity, the presence of obesity and sarcopenia together (4). This paradox is often characterised by fat infiltration of muscle; the increase in adipose tissue and decrease in muscle mass drastically alters metabolic processes and is closely associated with insulin resistance and diabetes (5).
What are the consequences of losing muscle mass?
As muscle mass makes up 60% of overall body tissue the structural and metabolic consequences of muscle loss are significant (2). This dramatic change in body composition can impact on mobility and lead to frailty, increased risk of falls and fractures, insulin resistance, fatigue and mortality. Sarcopenia can, of course, occur concurrently with other diseases such as rheumatoid arthritis or osteoporosis; when this is the case there is an even greater increase in the risk of fracture, illness and decreased quality of life.
Fortunately, with diet and lifestyle interventions the progression and severity of sarcopenia can be reduced.
Management of sarcopenia through nutrition and lifestyle
Nutrition and diet are the gold standard for the management or prevention of sarcopenia. Older adults generally have a greater relative protein requirement than younger adults. This is due to changes over time in ability to digest protein and, in the case of muscle, decreased sensitivity in older adults of muscle protein synthesis (‘MPS’) pathways. Whilst the current RDI is 0.8g/kg of body weight, recommended intake for older adults often ranges from 1.0 to 1.2g/kg of body weight. This may increase further in the case of chronic disease. The essential amino acid leucine is strongly associated with MPS and consumption of protein sources rich in this amino acid may help improve muscle strength and function (1 2, 6).
The aim should be to include 25-30g of protein with each main meal. Timing these meals post exercise may help increase muscle mass. Exercise programs focussing on resistance exercises, or a blend of both aerobic and resistance or compound exercises, can improve muscle strength and function as well as potentially increasing muscle mass in sarcopenic individuals (1).
Maintenance of overall physical activity, inclusion of resistance exercise and a diet containing sufficient energy and protein can be helpful in the prevention of sarcopenia and should be the cornerstone of a healthy lifestyle as we age (2, 6).
References
1. Cruz-Jentoft AJ, Landi F, Schneider SM, Zúñiga C, Arai H, Boirie Y, et al. (2014) Prevalence of and interventions for sarcopenia in ageing adults: a systematic review. Report of the International Sarcopenia Initiative (EWGSOP and IWGS). Age and ageing; 43, 748-59.
2. Walston JD (2012) Sarcopenia in older adults. Current opinion in rheumatology; 24, 623.
3. Scott D, Blizzard L, Fell J, Jones G (2011) The epidemiology of sarcopenia in community living older adults: what role does lifestyle play? Journal of cachexia, sarcopenia and muscle; 2, 125-34.
4. Cleasby ME, Jamieson PM, Atherton PJ (2016) Insulin resistance and sarcopenia: mechanistic links between common co-morbidities. Journal of Endocrinology; 229, R67-R81.
5. Stenholm S, Harris TB, Rantanen T, Visser M, Kritchevsky SB, Ferrucci L (2008) Sarcopenic obesity-definition, etiology and consequences. Current opinion in clinical nutrition and metabolic care; 11, 693.
6. Steffl M, Bohannon RW, Sontakova L, Tufano JJ, Shiells K, Holmerova I (2017) Relationship between sarcopenia and physical activity in older people: a systematic review and meta-analysis. Clinical interventions in aging; 12, 835.
Image from pixabay.com
