The definition of sarcopenia

Sarcopenia in old age has been associated with a higher mortality, poor physical functioning, poor outcome of surgery and higher drug toxicity. There is no general consensus on the definition of sarcopenia. The aim of the research presented in this thesis was to assess the implications of the use of different diagnostic criteria for sarcopenia, and to define the most accurate criteria for sarcopenia. Currently used diagnostic criteria for sarcopenia can be divided into criteria based on (1) low muscle mass, (2) low muscle strength, and (3) low walking speed. This thesis describes how muscle mass can be further divided into relative muscle mass and absolute muscle mass. A higher body or fat mass is associated with a lower relative muscle mass and with a higher absolute muscle mass. Higher relative muscle mass at old age is associated with better physical performance and with less insulin resistance. It is suggested to reserve the term sarcopenia to describe a low muscle mass and dynapenia to describe a low muscle strength. Most importantly, this research illustrates that it is impossible to compare studies about sarcopenia in scientific literature due to the use of different diagnostic criteria for sarcopenia.