Identification of biological markers for better characterization of older subjects with physical frailty and sarcopenia

Population aging is rapidly accelerating worldwide; however, longer life expectancy is not the only public health goal. Indeed, extended lifetime involves maintaining function and the capacity of living independently. Sarcopenia and physical frailty are both highly relevant entities with regards to functionality and autonomy of older adults. The concepts and definitions of frailty and sarcopenia have largely been revised over the years. Sarcopenia is an age-related progressive and generalized loss of skeletal muscle mass and strength. On the other hand, frailty is a state of increased vulnerability to stressors, responsible for exposing the older person to enhanced risk of adverse outcomes. Physical frailty and sarcopenia substantially overlap and several adverse outcomes of frailty are likely mediated by sarcopenia. Indeed, the concepts of sarcopenia and physical frailty can be perceived as related to the same target organ (i.e., skeletal muscle) and it may be possible to combine them into a unique definition. The biological background of such a close relationship needs to be explored and clarified as it can potentially provide novel and pivotal insights for the assessment and treatment of these conditions in old age. The aim of this paper is to indicate and discuss possible biological markers to be considered in the framing of physical frailty and sarcopenia.