The role of the circadian timing system in sarcopenia in old age: a scoping review

Purpose: Sarcopenia is a progressive and generalized skeletal muscle disorder, involving the accelerated loss of skeletal muscle mass and function, associated with an increased probability of adverse outcomes including falls. The circadian timing system may be involved in molecular pathways leading to sarcopenia in older adults. We aimed to provide an updated and systematic map of the available evidence on the role of the circadian timing system in sarcopenia, specifically related to the aging process. Methods: We developed a scoping review protocol following the PRISMA-ScR guidelines. Searches were conducted on PubMed, Scopus, Web of Science, Results: We identified 373 papers from three online databases, screened 97 for full-text analysis. and selected 37 papers for inclusion. These papers included 17 primary research studies on human persons, focusing on cortisol and melatonin secretion, rest-activity rhythms, chrono-exercise, and chrono-dietary regimens, 9 primary research studies on animal models (mice, rats, fruit flies) focusing on direct expression measurement or mutations of core clock genes, and 11 narrative reviews. Conclusion: While several reports supported the role of the circadian timing system in sarcopenia, specifically related to the aging process, the available evidence is fragmented and limited. The field is thus open to preclinical and clinical research that addresses the wide knowledge gaps in the available evidence, taking advantage of what has already been published to optimize and refine experimental and clinical protocols.