Читать книгу Pathy's Principles and Practice of Geriatric Medicine - Группа авторов - Страница 76

Peak muscle mass volume is achieved by 25 years from birth and is related to exercise and protein intake. After age 25, humans begin to gradually lose muscle mass and strength until the end of life. Sex steroids, testosterone and oestrogen, which decrease with age, contribute to muscle mass by their anabolic effect, in addition to nutrition and exercise. Skeletal muscle consists of muscle fibres, which are grouped into muscle cells. Muscle cells are rich in proteins like actin and myosin that form motor units. Muscle function depends on a motor unit structure, calcium, and ATP. Any impairment in one of these results in functional loss.⁸²

Muscle mass and muscle strength decrease with age because of the loss of motor units and muscle fibres. In addition, reduced protein synthesis causes muscle atrophy.⁸³ Muscle mass and muscle strength loss are defined as sarcopenia in older adults. Sarcopenia, as a geriatric syndrome, is related to frailty and mortality. Sarcopenia makes older adults more dependent and causes falls and fractures. The only way to prevent the progression of sarcopenia is to exercise regularly and have an adequate diet. Sarcopenia is diagnosed by European Working Group on Sarcopenia in Older People (EWGSOP) 2018 criteria as follows⁸⁴:

1 Low muscle strength

2 Low muscle quantity or quality

3 Low physical performance

If criterion 1 is present, probable sarcopenia can be diagnosed. If criteria 1 and 2 are present, sarcopenia can be diagnosed. And in the presence of all three, severe sarcopenia is diagnosed.

In the EWGSOP 2018 report, handgrip strength is measured using a hand dynamometer. Cut‐off levels for defining low muscle strength are <27 kg for men and <16 kg for women. Muscle quantity is measured by bioimpedance analysis. Appendicular muscle mass values of <20 kg for men and <15 kg for women are considered low muscle mass. Physical performance is measured by gait speed. A gait speed value of <8 m/s is considered to be low physical performance. Additional measurement methods for each of the criteria are described in detail in the EWGSOP 2018 report.