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Table 1 Participant characteristics

From: Molecular alterations in skeletal muscle in rheumatoid arthritis are related to disease activity, physical inactivity, and disability

Variable All participants (n = 102) Rheumatoid arthritis (n = 51) Matched controls (n = 51)
Age (years) 54.2 (12.5) 54.8 (13.2) 53.8 (11.9)
BMI (kg/m2) 30.0 (6.4) 30.3 (7.5) 29.6 (5.1)
Waist circumference (cm) 94.1 (15.2) 94.9 (16.8) 92.9 (13.3)
Race
 Caucasian 74 (72.6%) 36 (70.6%) 38 (74.5%)
 African American 27 (26.5%) 14 (27.5%) 13 (25.5%)
 Pacific Islander 1 (1.0%) 1 (2.0%) 0
Gender
 Female 72 (70.6%) 36 (70.6%) 36 (70.6%)
 Male 30 (29.4%) 15 (29.4%) 15 (29.4%)
Physical activity (kCal/day) 557.1 (280.8) 517.7 (279.4) 609.1 (278.7)
Physical activity (MET-hr/day) 5.4 (2.6) 4.9 (2.5) 6.0 (2.5)
Disease duration (months) NA 138.9 (136.3) NA
HAQ-disability index 0.46 (0.6) 0.68 (0.7)* 0.00 (0.0)
Comorbidity index 1.2 (1.2) 1.6 (1.1)* 0.6 (0.9)
DAS-28 mean (SD) NA 3.0 (1.4) NA
 Remission (DAS-28 < 2.6)   19 (40%)  
 Low activity (DAS-28 2.6‒3.2)   8 (17%)  
 Moderate activity (DAS-28 3.2‒5.1)   16 (33%)  
 High activity (DAS-28 > 5.1)   5 (10%)  
Rheumatoid factor positive NA 42/47 (89.4%) NA
Anti-cyclic citrullinated antibody positive NA 21/22 (95.6%) NA
Erosions present on radiographs NA 21/38 (55.2%) NA
Medication use NA   
 Etanercept   10 (19.6%) NA
 Infliximab   2 (3.9%) NA
 Adalimumab   5 (9.8%) NA
 Abatacept   5 (9.8%) NA
 Methotrexate   39 (76.5%) NA
 Leflunomide   1 (2.0%) NA
 Sulfasalazine   0 NA
 Hydroxychloroquine   10 (19.6%) NA
 Nonsteroidal anti-inflammatory agents   18 (35.3%)* 1 (4.0%)
 Prednisone (<5.0 mg/day)   13 (25.5%) NA
Systemic inflammation
 hsCRP (mg/L) 3.0 (3.9) 3.7 (4.9)* 2.4 (2.9)
 IL-1beta (pg/mL) 0.23 (5.3) 0.22 (4.1) 0.17 (6.4)
 IL-6 (pg/mL) 4.9 (2.8) 8.9 (2.9)* 2.7 (1.6)
 IL-8 (pg/mL) 8.2 (2.1) 8.9 (1.8) 7.5 (2.3)
 TNF-alpha (pg/mL) 13.7 (2.3) 19.9 (2.4)* 9.5 (1.7)
 IL-18 (pg/mL) 408.3 (1.4) 440.6 (1.3) 379.3 (1.4)
Adiposity and muscle tissue
 Abdominal total adipose area (cm2) 427.9 (181.0) 408.4 (199.5) 447.3 (160.2)
 Abdominal subcutaneous adiposity (cm2) 303.3 (143.7) 304.5 (154.2) 302.1 (133.9)
 Abdominal visceral adiposity (cm2) 124.6 (93.2) 104.0 (77.1)* 145.2 (103.6)
 Abdominal liver density (Hu) 59.0 (11.6) 59.7 (10.6) 58.2 (12.9)
 Thigh total area (cm2) 249.6 (65.4) 248.8 (73.6) 251.7 (57.1)
 Thigh total adipose area (cm2) 250.2 (66.0) 134.3 (65.8) 110.9 (68.0)
 Thigh subcutaneous adiposity (cm2) 122.6 (67.6) 122.6 (62.7) 113.8 (54.0)
 Thigh inter-muscular adiposity (cm2) 11.3 (7.4) 11.7 (6.7) 11.0 (8.1)
 Thigh muscle area (cm2) 119.6 (35.1) 114.5 (37.1) 125.4 (32.1)
 Thigh muscle density (Hu) 54.0 (8.1) 50.7 (6.2) 55.4 (6.8)
Skeletal muscle inflammatory markers
 IL-1β (pg/mL/mg) 0.035 (0.084) 0.037 (0.093) 0.033 (0.069)
 IL-6 (pg/mL/mg) 0.012 (0.010) 0.014 (0.010)* 0.008 (0.007)
 IL-8 (pg/mL/mg) 0.139 (0.178) 0.169 (0.211) 0.097 (0.106)
 TNF-α (pg/mL/mg) 0.012 (0.015) 0.014 (0.016) 0.010 (0.014)
 TLR4 (pg/mL/mg) 0.891 (0.666) 0.859 (0.692) 0.937 (0.625)
  1. Data are presented as means (SD) for continuous variables and number (percentages) of participants for dichotomous variables. Data that were not normally distributed (systemic inflammatory markers and cytokines) are presented as geometric means (SD). Physical activity data reflect rheumatoid arthritis (RA) (n = 41) and controls (n = 31) with valid data. BMI body mass index, MET metabolic equivalents, HAQ health assessment questionnaire, DAS-28 disease activity score with 28-joint count, hsCRP high sensitivity C-reactive protein, IL interleukin, TNF tumor necrosis factor, Hu Houndsfield units, TLR toll-like receptor
  2. * p < 0.05 for comparison with matched controls