Sarcopenia in osteoarthritis and rheumatoid arthritis: The association with self-reported fatigue, physical function and obesity

Aim To determine if there is an association between sarcopenia, physical function and self reported fatigue in osteoarthritis (OA) and rheumatoid arthritis (RA). Methods A cross-sectional analysis of measurements from a cohort of 157 participants with OA or RA was performed. The relationship between muscle mass (appendicular muscle index (AMI)), physical function (timed up and go, 30-seconds sit-to-stand test, 40-meter fast-paced walk test and grip-strength) and two fatigue measures (Multidimensional Assessment of Fatigue (MAF) and a fatigue Visual Analogue Scale (VAS)) was explored using hierarchical linear regression or logistic regression with established AMI cut-offs for sarcopenia. Results There were no significant differences for perceived fatigue-related variables between OA or RA sarcopenic or non-sarcopenic participants. Participants with OA had worse physical function (TUG; P=0.029, STS; P=0.004, WS; P=0.003), but participants with RA had lower grip strength (P<0.001). The RA group had higher CRP (P=0.006), were more likely to receive glucocorticoids (P<0.001), and experienced worse fatigue (P=0.050). The hierarchical multiple regression showed that self-reported fatigue (VAS/MAF-distress) had a significant but weak association with AMI in RA. Participants with higher percentage body fat had a significantly stronger association with sarcopenia in both OA and RA. Conclusion Sarcopenia, when assessed by AMI, does not appear to be strongly associated with self reported fatigue or physical function in participants with either OA or RA. Higher body fat had a moderately strong association with sarcopenia in this cross-sectional study, suggesting that body composition may be an important factor in the health of patients with longstanding OA or RA.