Bioelectric Phase Angle and Appendicular Skeletal Muscle Mass in Rheumatoid Arthritis: Association With Disease Activity, Impact of Disease, and Functional Disability.

OBJECTIVE

Adverse changes in body composition are increasingly being recognized in patients with rheumatoid arthritis (RA). This study aimed to explore the relationship between RA disease activity, disease impact, and functional disability with bioelectrical phase angle (PhA) and appendicular skeletal muscle mass index (ASMI).

METHODS

Patients with RA were recruited at a tertiary hospital in Portugal. The Disease Activity Score in 28 joints based on erythrocyte sedimentation rate and C-reactive protein (DAS28-ESR and DAS28-CRP, respectively) were used to assess disease activity. The impact of disease and functional status were evaluated using the Rheumatoid Arthritis Impact of Disease (RAID) questionnaire and the Health Assessment Questionnaire (HAQ), respectively. Body composition was measured by bioelectrical impedance analysis (BIA). PhA was stratified into tertiles, and ASMI was classified according to the European Working Group on Sarcopenia in Older People 2 criteria.

RESULTS

A total of 104 patients with RA were included (74% female; mean age 60.9 [SD 9.6] years). RAID scores were significantly lower in patients in the highest PhA tertile (PhA-T3) than in those in the lower PhA tertiles (PhA-T2 and PhA-T1, P = 0.001 and P < 0.001, respectively). HAQ scores were significantly lower in patients in the highest PhA tertile (PhA-T3) than in those in the lowest PhA tertile (PhA-T1, P < 0.001). Median DAS28-ESR and DAS28-CRP were lower among patients with higher PhA, but the difference did not reach statistical significance (P = 0.07 and P = 0.16, respectively). No differences were found among the ASMI groups in DAS28-ESR (P = 0.62), DAS28-CRP (P = 0.97), RAID (P = 0.30), or HAQ (P = 0.51) scores.

CONCLUSION

A lower PhA was associated with greater disease impact and greater significant functional disability in patients with RA.