Sarcopenia and rheumatic diseases: is there any connection?

Abstract

Sarcopenia is characterized by a loss of skeletal muscle mass, a decrease in muscle strength and/or physical performance, and is one of the main causes for limiting daily activities in the elderly. This is associated with an increased incidence of many adverse events such as dysfunction, falls, frailty, hospitalization, disability, and mortality. Primary (considered as a part of the aging process) and secondary sarcopenia (due to malabsorption, immobility/bed rest, starvation, hypothyroidism, osteoporosis, immune-mediated rheumatic diseases) are united by a chronic inflammatory process of different degrees. Sarcopenia supports one of the most widely accepted theories that low-grade chro­nic inflammation is important in the pathogenesis of many di­seases. For a long time, sarcopenia was considered an age-related disease, but recently it has been reported to be more common in young subjects with autoimmune diseases. In particular, the relationship between sarcopenia and rheumatic diseases such as rheumatoid arthritis has been studied in detail. Although the pathogenesis of sarcopenia in autoimmune diseases is not fully understood, it is believed that a chronic inflammatory process contri­butes to the development of loss of muscle mass and strength, and is different depending on the underlying disease. The definition of sarcopenia varies between studies, which complicates and li­mits direct comparisons. Therefore, in this review, we demonstrate various diagnostic criteria for sarcopenia, focusing on its pre­valence in patients with rheumatic diseases, including rheumatoid arthritis, juvenile idiopathic arthritis, axial spondylitis, psoriatic arthritis, and systemic sclerosis. We developed a structured search strategy for English language publications in PubMed using the term “sarcopenia” in combination with the following keywords: “inflammation”, “diagnosis”, “criteria”, “muscle mass”, “strength”, “outcomes”, “disability”, “mortality”, “pathophysiology”, “rheumatoid arthritis”, “juvenile arthritis”, “axial spondylitis”, “psoriatic arthritis”, “systemic sclerosis”. We focused on clinical trials, meta-analyses and review articles. Articles published only after 2000 year were included, however, we did not include major contributions published before. The search was completed on October 8, 2022.