Sarcopenia

Sarcopenia is defined as:

The age-related decline in skeletal muscle mass concomitant with decreased strength and/or function. 

The term sarcopenia was only coined recently in 1989 and is derived from the Greek words sarco meaning flesh and penia meaning poverty. Sarcopenia can be chronic or acute, with the chronic form being more common and acute sarcopenia usually following a hospital stay or prolonged bed rest. Sarcopenia is an inevitable part of ageing. 

Studies suggest that after the age of 40, adults lose approximately 8% of their muscle mass every 10 years. Past the age of 70 years, the rate of loss increases to 15% per decade. This means between age 40-70, healthy adults lose on average 24% of muscle mass. 

As we age, not only do we lose muscle mass, but the quality of our muscle tissue changes. There is an infiltration of fatty tissue, less mitochondria and neurological changes that affect the amount of strength a muscle contraction can generate. We have a reduction in our fast twitch muscle fibres which causes a reduction in muscle power.

Prevalence of sarcopenia varies according to the setting. One study suggests rates of 1-29% in community dwelling adults, 14-33% in those in a long term care setting and up to 10% of those in acute hospital care. Up to 60-70% of critically ill patients in intensive care have been seen to have sarcopenia. 

Although some loss of muscle mass will be inevitable with ageing, one study found that the loss is slowed amongst those that are more physically active. This study found those participating in moderate-vigorous physical activity lost 9% of muscle mass over five years, compared to least active individuals - 14.8%.

A strong relationship exists between muscle mass and function. Sarcopenia comes with an increased risk of falls, physical disability and reduced quality of life. Low muscle mass has been linked with hospital admissions, extended hospital stays, fractures, gait disorders and mortality. One study showed that individuals with sarcopenia are over three times more likely to fall, compared to those without sarcopenia. 

Apart from lack of physical activity, there are many age related changes that can affect our muscle function such as inflammation and hormonal changes. As we age we have an increase in inflammation. This chronic inflammation has been directly linked with loss of muscle mass and reduced strength. In women, loss of oestrogen has not only been linked with lower muscle mass and strength but with higher levels of inflammation. We also see a loss of neurons which means our muscle contractions become slower. Other factors that can cause a decline in our skeletal muscle health include endocrine disorders such as diabetes and nutrition, specifically lack of protein and lower energy intake.

Whilst imaging can be used in the diagnosis of sarcopenia, in the clinic we can assess muscle strength and physical function. Measuring grip strength is commonly used in the diagnosis of sarcopenia and grip strength has been strongly correlated to lower extremity muscle power and calf muscle mass. We can look at walking speed and strength of the legs which have both been linked to sarcopenia.  

Whilst some age-related changes to muscle mass and strength are expected, we can slow the rate of decline. At this point in time, no medication has been proved beneficial in treating sarcopenia. The current recommendations involve addressing nutrition and participating in a progressive strengthening program. Protein, energy intake and vitamin D deficiency all need to be addressed for optimal muscle performance and strength gains. Resistance training focusing on developing power has been shown the most important for functional independence and quality of life.