Bioelectrical impedance analysis (BIA) -derived phase angle in sarcopenia: A systematic review

Bioelectrical impedance analysis-derived phase angle (PhA) has been gaining attention in the clinical evaluation of nutritional status because it is thought to be a proxy of water distribution and body cell mass; it is also associated to muscle strength and is an effective predictor of different clinical outcomes. Since an association may be expected between PhA and sarcopenia (defined by low skeletal muscle mass and impaired muscle function), the aim of this systematic review was to evaluate: a) changes in PhA due to sarcopenia; b) prevalence of sarcopenia according to PhA values; c) derivation of phase angle cut-offs for detecting sarcopenia; d) sarcopenia and PhA as predictors of clinical outcomes.

A systematic research on electronic databases (PubMed, Embase, Scopus and Web of Science) from inception to January 31st, 2020 was performed according to PRISMA checklist. Using PICOS strategy, "P" corresponded to participants of any age, gender or ethnicity, "I" designated diagnosis of sarcopenia, "C" indicated subjects without sarcopenia, "O" corresponded to PhA, and "S" selected all study types. Methodological quality was assessed using the National Institute of Health (NIH) quality assessment tool.

Through the initial literature search and after removing duplicates and excluding papers by screening titles and abstracts, 79 potentially relevant studies were examined. Thirteen studies (7668 subjects) met the inclusion criteria. The overall risk of bias was low. Sarcopenia was associated with a significant lower PhA in seven studies out of eight, while five studies out of six reported a high prevalence of sarcopenia was in patients with low PhA. Different cut-off point values from 4.05 to 5.05° have been derived for the identification of sarcopenia. PhA and sarcopenia were independent predictors of survival in cancer patients and geriatric hospitalized patients.

Data from the selected papers demonstrate that PhA is decreased in sarcopenic subjects and the prevalence of sarcopenia is higher in subjects with low PhA. Further studies are needed to determine to what extent PhA may be valuable in detecting low muscle quality and/or identifying sarcopenia.