<p><strong>PURPOSE: </strong>Rheumatoid arthritis (RA) is associated with low muscle density due to accumulation of intramuscular fat. This study identified predictors of changes in muscle density and determined whether low muscle density predicted changes in strength and physical function.</p>

<p><strong>METHODS: </strong>Patients with RA, ages 18-70, completed whole-body DXA and peripheral quantitative CT (pQCT) to quantify lean and fat mass indices and muscle density. Dynamometry was used to measure strength at the hand, knee, and lower leg. Disability and physical function were measured with the Health Assessment Questionnaire (HAQ) and the Short Physical Performance Battery (SPPB). Assessments were performed at baseline and at follow-up. Regression analyses assessed associations between patient characteristics, muscle density, and deteriorations in strength and function.</p>

<p><strong>RESULTS: </strong>Muscle density was assessed at baseline in 107 patients with RA. Seventy-nine (74%) returned for a follow-up assessment at a median follow-up time of 2.71 years (IQR: 2.35-3.57). Factors associated with declines in muscle density included female sex, higher disease activity, smoking, and lower IGF-1 levels. Greater muscle density Z-Score at baseline (per 1 SD) was associated with less worsening per year of HAQ, SPPB, and 4-meter walk time and a lower risk of a clinically important worsening in HAQ [OR 1.90 (1.06,3.42) p=0.03] and walking speed [OR 2.87 (1.05,7.89) p=0.04].</p>

<p><strong>CONCLUSION: </strong>Worsening of skeletal muscle density occurred in patients with higher disease activity, smokers, and those with lower IGF-1. Low muscle density was associated with worsening of physical function. Interventions addressing reductions in muscle quality might prevent functional decline.</p>

<p><strong>BACKGROUND &amp; AIMS: </strong>Celiac disease can reduce bone mineral density. We sought to determine the prevalence and risk factors for low areal bone mineral density (aBMD) in children with celiac disease.</p>

<p><strong>METHODS: </strong>We performed a retrospective cohort study of 673 children with celiac disease (63% female; median age at diagnosis, 10.6 y; interquartile range, 7.8-13.9) who underwent dual x-ray absorptiometry (DXA) from 2009 through 2016 at the Children's Hospital of Philadelphia. We collected demographic, clinical, and laboratory data from medical records. We performed logistic regression analysis to identify factors associated with low (Z less than -2) lumbar spine aBMD Z (aBMD-Z) scores at initial and subsequent tests.</p>

<p><strong>RESULTS: </strong>The time between diagnosis of celiac disease and first DXA was 0 days (interquartile range, -11 to 31 d). The mean aBMD-Z score at the children's initial scan was -0.4 ± 1.2; 46 children had aBMD-Z scores less than -2 (6.8%; 95% CI, 5.2%-9.0%). Those who had a second DXA analysis (n&nbsp;= 108; 16.0%) had a significant increase in aBMD-Z score (mean change, 0.29; P&nbsp;= .0005). Higher body mass index (BMI) was associated with lower odds of a low aBMD-Z score at the initial DXA analysis (odds ratio, 0.46, 95% CI, 0.35-0.50). BMI-Z scores greater than -0.4 identified children with a low aBMD-Z at their initial DXA analysis with a 95% negative predictive value.</p>

<p><strong>CONCLUSIONS: </strong>Approximately 7% of subjects with celiac disease had a low aBMD-Z score, determined by DXA, at the time of diagnosis; this value was nearly 3-fold higher than expected from a population of children of this age and sex distribution. BMI-Z scores could be used to identify children with celiac disease at risk for low BMD who should receive DXA screening.</p>

<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 (&gt;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>