Higher Prevalence of Sarcopenia Reported in Patients with Rheumatoid Arthritis

Sarcopenia, an age-related loss of muscle mass and depletion of strength and performance, is significantly more common in patients with rheumatoid arthritis (RA) when compared with controls when assessed using the updated European Working Group on Sarcopenia in Older People (EWGSOP2) criteria. Further, the Foundation for the National Institutes of Health (FNIH) definition showed a higher proportion of participants with sarcopenia in individuals with high body mass index (BMI) and fat mass, regardless of RA diagnosis, according to a study published in Rheumatic & Musculoskeletal Diseases.¹

“Currently, no consensus definition for sarcopenia exists,” investigators explained. “However, all definitions proposed recently include the assessment of muscle mass and muscle strength, yet different thresholds are being applied to determine these parameters. Hence, the existing data on the prevalence of sarcopenia vary, depending on the definition used and the respective population studied. However, it is well known that sarcopenia increases with advanced age. Whereas the amount of sarcopenia is found to be around 15% in 65 years, it rises up to 40% in 85-year-old healthy ambulatory subjects.”

The single-center, cross-sectional study, performed at the Charité—Universitätsmedizin Berlin, included 289 adult patients with RA. Appendicular lean was measured via dual x-ray absorptiometry and muscle function, including chair rise time, gait speed, and grip strength was assessed. EWGSOP2 and FNIH assessed the prevalence of sarcopenia. Patients with RA were then compared with a cohort of healthy controls (n = 280).

The mean age of patients in the RA cohort was 59 years, 80% were women, the median disease duration was 9 years, and most had a low disease activity score. Among patients with RA, 4.5%, (59.4±11.3 years) were affected by sarcopenia, compared with 0.4% of controls (62.9±11.9 years) by EWGSOP2 definition. Of those with RA, body weight (odds ratio [OR] 0.92, 95% CI 0.86 to 0.97), BMI (OR 0.70, 95% CI 0.57 to 0.87), disease duration (OR 1.08, 95% CI 1.02 to 1.36), current medication with glucocorticoids (OR 5.25, 95% CI 2.14 to 24.18), cumulative dose of prednisone equivalent (OR 1.04, 95% CI 1.02 to 1.05), C reactive protein (CRP) (OR 1.05, 95% CI 1.01 to 1.10), and Health Assessment Questionnaire (HAQ) (OR 2.50, 95% CI 1.27 to 4.86) were associated with a sarcopenia diagnosis.

However, when using the FNIH definition, 2.8% of patients with RA and 0.7% of controls were affected by sarcopenia. In these participants, smaller body height (OR 0.75, 95% CI 0.64 to 0.88), higher BMI (OR 1.20, 95% CI 1.02 to 1.41), higher CRP (OR 1.06, 95% CI 1.01 to 1.11), and higher HAQ (OR 2.77, 95% CI 1.17 to 6.59) were linked to sarcopenia.

The cross-sectional design of the study, which did not allow for the determination of a causal relationship between sarcopenia and contributing factors, limited the study. Applying the same criteria to a control group without inflammatory disease showed that patients with RA are more likely to be affected by sarcopenia, low lean mass, and poor muscle function. However, it could not be determined whether patients with joint pain or joint destruction, caused by RA, impacted grip strength. Therefore, assessments may have been influenced by factors unrelated to muscle function. Future studies should evaluate the influence of pain and erosive lesions. Other studies are needed to determine risk factors and cut-off values for muscle mass and muscle function.

“This research is a first step towards a deeper understanding of defining low muscle mass by using different muscle mass indices,” investigators concluded. “The 2 definitions were found to respond differently to the anthropometric characteristics of the cohort, resulting in different rates of prevalence. This shows the importance of a common definition of sarcopenia and the need for reliable methods to determine low muscle mass and the inclusion of muscle function.”

Reference:

Dietzel R, Wiegmann S, Borucki D, et al. Prevalence of sarcopenia in patients with rheumatoid arthritis using the revised EWGSOP2 and the FNIH definition. RMD Open. 2022;8(2):e002600. doi:10.1136/rmdopen-2022-002600