Low Muscle Strength, Bone Mineral Density Observed in Juvenile Idiopathic Arthritis

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Muscle strength and bone health were suboptimal in patients with oligo- and polyarticular juvenile idiopathic arthritis compared with controls.

Individuals with juvenile idiopathic arthritis (JIA) have lower bone mineral density (BMD) and muscular strength compared with healthy controls, according to a study recently published in Arthritis Care & Research. However, cardiorespiratory fitness and body composition did not differ between the groups, highlighting the importance of vigorous physical activity in individuals with JIA.

This cohort study recruited 60 participants with JIA and 60 healthy controls matched for age and gender. Participants in this study were 83% female and aged between 10 and 16 years. Cardiorespiratory fitness was measured using peak uptake of oxygen on a treadmill, and muscle strength was examined through isokinetic and isometric assessments of the knee and hand. Measures of muscular strength included grip, quadriceps, and hamstring strength.

Accelerometry was used to gauge physical activity for 7 successive days. Dual energy x-ray absorptiometry was used to study BMD and body composition and included anterior and posterior projections of the entire body.

Those in the study cohort (40 of whom had active disease and 20 inactive) had lower muscular strength and whole-body BMD than controls, but body composition and cardiorespiratory fitness were similar.

Participants with persistent oligoarticular disease (n=30) had similar levels of physical fitness as those with extended oligo- and polyarticular disease (n=30), but ventilatory efficiency was higher in the extended oligo- and polyarticular subgroup. A higher rate of vigorous physical activity was associated with greater cardiorespiratory fitness and muscular strength across both of these subgroups. Physical fitness did not correlate with disease variables.

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The study researchers conclude that “patients with oligo- and polyarticular JIA diagnosed in the era of biologics have similar [cardiorespiratory fitness] and body composition but lower muscle strength and bone health than matched healthy controls. All components of physical fitness are comparable between patients with persistent oligoarthritis and polyarticular disease. Higher levels of [vigorous physical activity] are associated with higher [cardiorespiratory fitness] and muscle strength in JIA patients.”

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Risum K, Edvardsen E, Godang K, et al. Physical fitness in patients with oligo- and polyarticular juvenile idiopathic arthritis diagnosed in the era of biologics – A controlled cross-sectional study [published online November 26, 2018]. Arthritis Care Res. doi:10.1002/acr.23818