Intramuscular Fat Accumulation and Associations with Body Composition, Strength and Physical Functioning in Rheumatoid Arthritis.
Year of Publication
2018 Feb 26
<p><strong>PURPOSE: </strong>Rheumatoid arthritis (RA) is associated with adverse body composition profiles, and low muscle density due to accumulation of intramuscular fat. This study assessed associations between muscle density, body composition, muscle strength, and physical functioning in patients with RA and a reference group.</p>
<p><strong>METHODS: </strong>Patients with RA, ages 18-70 years, and healthy control participants completed whole-body DXA and peripheral quantitative CT (pQCT) to quantify appendicular lean mass (ALMI, kg/m) and fat mass indices (FMI, kg/m), visceral fat area, and muscle density. Dynamometry was used to measure hand-grip strength and muscle strength at the knee and lower leg (ft-lbs). Disability and physical functioning were measured with the Health Assessment Questionnaire (HAQ) and the Short Physical Performance Battery (SPPB). Linear regression analyses assessed differences related to RA and associations between muscle density, strength, and function.</p>
<p><strong>RESULTS: </strong>The study consisted of 103 RA patients (51 men) and 428 healthy participants. Low muscle density was associated with greater disease activity, CRP, and Interleukin-6, greater total and visceral fat, lower ALMI Z-Scores, physical inactivity, and long-term use of glucocorticoids (>1yr). Patients with low ALMI Z-Scores had lower muscle density Z-Score compared to reference participants with similarly low ALMI. Low muscle density was independently associated with lower muscle strength, higher HAQ, and lower SPPB after adjusting for ALMI and FMI Z-Scores.</p>
<p><strong>CONCLUSIONS: </strong>Low muscle density observed among patients with RA is observed in association with low muscle mass, excess adiposity, poor strength, and greater disability. Interventions to address poor muscle quality could potentially affect important functional outcomes. This article is protected by copyright. All rights reserved.</p>
Arthritis Care Res (Hoboken)