Sarcopenia: a common muscle condition in older adults with type 2 diabetes

Diabetes, particularly type 2 diabetes, is a chronic condition that is more prevalent in older adults. One in five adults over the age of 65 is estimated to be living with diabetes (1). Characteristics of the ageing process, such as loss of skeletal muscle mass and higher total body fat, are linked with an increased risk of developing metabolic disorders such as type 2 diabetes (2,3,4). Type 2 diabetes is associated with an increased risk of developing a number of serious and potentially life threatening complications (5).

Complications of type 2 diabetes result from chronic high blood glucose (hyperglycaemia), the accumulation of Advanced glycation end-products (AGEs, harmful compounds that are formed when protein or fat combine with glucose in the bloodstream), inflammation and oxidative stress. All of these can affect skeletal muscle (6,7).

What is sarcopenia?

Sarcopenia is a common and progressive skeletal muscle condition associated with an increased risk of falls, fractures, physical disability and death (8). Low muscle strength is considered as the main indicator of sarcopenia (8).

Sarcopenia was first described in the late 1980s as a progressive loss of skeletal muscle mass associated with ageing. It is now also recognised to be associated with a deterioration in muscle quality, strength and performance (9). Sarcopenia is linked to a number of changes that also occur when people get older, such as reduced levels of physical activity, changes in endocrine function (lower testosterone, growth hormone and oestrogen levels), insulin resistance and the increased need for protein in the diet (9,10). Older adults with type 2 diabetes appear to be at increased risk (11).

Diagnosing sarcopenia

Sarcopenia is considered probable when low muscle strength is detected. A diagnosis is confirmed when there is a low quantity or quality of muscle. The condition is considered serious when low muscle strength, quantity or quality is combined with poor physical performance(12). In clinical practice, a diagnosis begins when a person reports signs or symptoms such as falling, feeling weak, walking slowly, difficulty getting up from a chair or weight loss. In such cases, further tests are recommended (13).

There are a number of ways to detect the presence of sarcopenia and a variety of methods are being explored to determine the quantity and quality of muscle and the impact of sarcopenia on the quality of life of people affected (14). Methods of detection include:

Assessing muscle mass: anthropometry (measuring the proportions of the human body) has been used to reflect the nutritional status of older adults, but it is not a good indicator of muscle mass. Calf circumference can predict performance and survival in older people and is used as a diagnostic indicator in settings where other methods of diagnosing muscle mass are not available (15). Computerised Tomography (CT Scan) and Magnetic Resonance Imaging (MRI) are considered optimal methods to estimate muscle mass, but due to cost and difficulty of access are not as useful in daily clinical practice (15).

Evaluating muscle strength: a hand dynamometer (or handgrip test) is used to measure the maximum isometric (static) strength of the hand and forearm muscles.

Evaluating physical performance: involving an assessment of the central and peripheral nervous systems and muscular area (15). A walking speed test is considered to be quick, safe and very reliable. The most commonly used is the 4-metre walk, with speed measured in time.

Prevention and treatment of sarcopenia

Physical Activity

Lack of physical activity has been associated with loss of strength and muscle mass (16). Regular exercise is therefore the cornerstone of prevention and treatment of sarcopenia. Resistance exercises in particular have been shown to increase the combination of proteins at the muscle level (17). Treatment with regular exercise should last at least three months to achieve an impact on muscle function (18). For people aged 65 and over, physical activity should be daily and include aerobic activities such as walking or cycling. Physiotherapy can also be very effective for people who have lost muscle mass and need to increase their strength (18).

Nutrition

Protein is important for maintaining and increasing skeletal muscle. In older adults, a daily intake of protein of between 1.2 and 1.6g is recommended (19). However, the benefits of protein supplements in improving exercise-related muscle outcomes in older adults with and without sarcopenia remain unclear (20). Low levels of vitamin D have been linked to poor physical function and glycaemic control. Research suggests that vitamin D supplements may improve muscle strength (21-23).

Diabetes medication:

A clinical trial is currently underway to investigate the potential benefits of metformin as an additional therapy to resistance training in older adults, since it may have anti-inflammatory properties on skeletal muscle (24). Insulin can increase muscle mass and protein metabolism in young people without insulin resistance, but does not appear to have the same effect in people with type 2 diabetes (25).

Summary

• There are several links between type 2 diabetes and sarcopenia. Having one can increase the risk of developing the other.
• Factors such as insulin resistance, inflammation, AGE accumulation, increased oxidative stress and vascular complications can affect several components of muscle health.
• Evidence suggests that various lifestyle interventions can improve and maintain functional and metabolic health in all people, including those with type 2 diabetes and sarcopenia.
• Preventative measures can best ensure physical and functional well-being in people with diabetes as they grow older and also help prevent or delay the onset of type 2 diabetes in people at risk.

References

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