Decreasing muscle performance associated with increasing disease activity in patients with rheumatoid arthritis

Increasing evidence suggests that inflammation has a detrimental effect on muscle strength. Our objective was to analyse the association between muscle performance and different disease activity levels in patients with rheumatoid arthritis (RA).

A total of 199 consecutive outpatients were subject to cross-sectional assessment. Measurements of grip strength, endurance of the upper and lower limbs and trunk strength were combined as a muscle performance composite score (MPCS), using a standardised method. The disease activity for 28 joints (DAS28), radiographs of small joints (Larsen score), rheumatoid factor, body mass index (BMI), comorbidities and anti-rheumatic drugs were verified. Patients' questionnaires included sociodemographic information, pain level, global disease activity, the Beck Depression Inventory, the mental and physical component scores of Short Form-36 and physical activity level.

Of the 199 patients, 36%, 17% and 47% patients had remission, low/moderate and high DAS28, respectively. The patients in remission had significantly shorter disease duration, better parameters in terms of pain, physician's assessment, Larsen, Beck or physical component score of Short Form-36, and they were more physically active than other patients. After adjustments for age, sex, RA duration, radiographs and BMI, the decreasing MPCS associated linearly with the increasing DAS28 activity levels (linearity, P <0.001).

Poorer MPCS is clearly associated with higher disease activity in patients with RA. Muscle performance is a modifiable risk factor. The findings suggest evaluating muscle performance in clinical practice as a part of patient care.