Article Figures & Data
Tables
- Table 1.
Participant characteristics. Data are presented as means (SD) for continuous variables and number (%) of participants for dichotomous variables. Data that were not normally distributed (systemic inflammatory markers, cytokines, and insulin sensitivity) are presented as geometric means (SD).
Variable All Participants, n = 78 Rheumatoid Arthritis, n = 39 Matched Controls, n = 39 Age, yrs 55.5 (11.8) 56.1 (12.4) 54.9 (11.4) BMI, kg/m2 30.2 (6.3) 30.5 (7.3) 30.0 (5.3) Waist circumference, cm 94.9 (15.5) 95.1 (17.7) 94.6 (13.7) Race White 59 (76) 29 (74) 30 (76) African American 19 (24) 10 (26) 9 (24) Sex Female 54 (69) 27 (69) 27 (69) Male 24 (32) 12 (31) 12 (31) Physical activity, kCal/day 572.8 (290.8) 546.6 (291.4) 605.1 (292.7) Physical activity, METS h/day 29.5 (2.5) 29.2 (2.5) 29.9 (2.4) Disease duration, mos NA 159 (135) NA HAQ–Disability Index 0.5 (0.7) 0.7 (0.7)† 0.00 (0.00) Comorbidity Index 1.2 (1.2) 1.5 (1.2) † 0.6 (0.9) DAS28 mean (SD) NA 3.1 (1.5) NA Remission (DAS28 < 2.6) 16 (42) Low activity (DAS28 2.6–3.2) 6 (16) Moderate activity (DAS28 3.2–5.1) 11 (29) High activity (DAS28 > 5.1) 5 (13) Rheumatoid factor–positive NA 30/35 (86) NA Anticyclic citrullinated antibody-positive NA 14/15 (93) NA Erosions on radiographs present NA 18/30 (60) NA Medication use NA Etanercept 8 (21) NA Infliximab 2 (5) NA Adalimumab 4 (10) NA Abatacept 5 (13) NA Methotrexate 29 (74) NA Leflunomide 1 (3) NA Sulfasalazine 0 NA Hydroxychloroquine 6 (13) NA Nonsteroidal antiinflammatory agents 16 (41) 1 (5.5) Prednisone (< 0.5 mg/day) 11 (28) NA Systemic inflammation hsCRP, mg/l 3.14 (4.1) 4.1 (5.5) 2.4 (2.9) IL-1β, pg/ml 0.22 (5.4) 0.32 (4.2) 0.15 (6.3) IL-6, pg/ml 5.3 (2.8) 9.9 (2.9)† 2.9 (1.6) IL-8, pg/ml 8.5 (2.1) 9.4 (1.9) 7.7 (2.4) TNF-α, pg/ml 14.1 (2.3) 21.6 (2.4)† 9.4 (1.6) IL-18, pg/ml 413.0 (1.3) 446.7 (1.2)† 316.2 (1.4) Insulin Sensitivity Index 10−5 min−1/pmol/l All 4.5 (2.2) 4.0 (2.4) 4.9 (2.1) Women 5.0 (2.3) 4.7 (2.4) 5.2 (2.2) Men 3.6 (2.1) 3.1 (2.3) 4.0 (1.9) Biologic use = yes NA 4.8 (2.4) NA Biologic use = no NA 3.7(2.4) NA DMARD use = yes NA 4.0 (2.5) NA DMARD use = no NA 5.4 (1.7) NA Prednisone use = yes NA 3.2 (2.1) NA Prednisone use = no NA 4.8 (2.4) NA NEFA (mmol/l) 0.55 (1.47) 0.57 (1.57) 0.53 (1.36) Adiposity and muscle tissue Abdominal total adipose area, cm2 430 (179) 407 (199) 453 (157) Abdominal subcutaneous adiposity, cm2 306 (144) 302 (149) 309 (141) Abdominal visceral adiposity, cm2 125 (98) 105 (81)† 144 (109) Abdominal liver density, Hu 60 (10) 60 (9) 60 (10) Thigh total area, cm2 254 (65) 253 (69) 255 (61) Thigh total adipose area, cm2 127 (66) 137 (61) 116 (70) Thigh subcutaneous adiposity, cm2 121 (57) 125 (58) 117 (57) Thigh intermuscular adiposity, cm2 11 (8) 12 (7) 11 (8) Thigh muscle area, cm2 120 (36) 116 (39) 125 (33) Thigh muscle density, Hu 51 (5) 50 (6) 52 (4) -
↵† p < 0.05 for comparison with matched controls. BMI: body mass index; NA: not applicable; HAQ: Health Assessment Questionnaire; DAS28: 28-joint Disease Activity Score; hsCRP: high-sensitivity C-reactive protein; IL: interleukin; METS: metabolic equivalence units; TNF: tumor necrosis factor; DMARD: disease-modifying antirheumatic drugs; NEFA: nonesterified free fatty acids.
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Variable Spearman ρ (R) p Age, yrs −0.16 0.29 BMI, kg/m2 −0.45 0.002 Waist circumference, cm −0.47 0.001 Sex (male = 0, female = 1) 0.20 0.20 Physical activity, kCal/day −0.08 0.66 Physical activity, METS h/day 0.19 0.27 Disease duration 0.16 0.32 HAQ Disability Index −0.21 0.17 DAS28 −0.12 0.44 Biologic use, yes = 1, no = 0 0.14 0.37 DMARD use, yes = 1, no = 0 −0.16 0.29 Prednisone use, yes = 1, no = 0 −0.28 0.07 hsCRP, mg/l −0.18 0.25 IL-1β, pg/ml 0.04 0.82 IL-6, pg/ml −0.30 0.05 IL-8, pg/ml −0.09 0.56 TNF-α, pg/ml −0.08 0.62 IL-18 (pg/ml) −0.20 0.20 NEFA −0.28 0.06 Abdominal total adipose area, cm2 −0.43 0.005 Abdominal subcutaneous adiposity, cm2 −0.30 0.06 Abdominal visceral adiposity, cm2 −0.48 0.002 Abdominal liver density, Hu 0.27 0.10 Thigh total area, cm2 −0.38 0.01 Thigh total adipose area, cm2 −0.20 0.20 Thigh subcutaneous adiposity, cm2 −0.15 0.32 Thigh intermuscular adiposity, cm2 −0.52 0.0004 Thigh muscle area, cm2 −0.36 0.02 Thigh muscle density, Hu 0.12 0.45 -
Data given in bold face are statistically significant. BMI: body mass index; HAQ: Health Assessment Questionnaire; DAS28: 28-joint Disease Activity Score; DMARD: nonbiologic disease-modifying antirheumatic drug; hsCRP: high-sensitivity C-reactive protein; METS: metabolic equivalence units; IL: interleukin; TNF: tumor necrosis factor; NEFA: nonesterified free fatty acids.
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- Table 3.
Multivariable model for insulin sensitivity index (log) in persons with rheumatoid arthritis.
Variable Estimate Partial R2 p Clinical model: R2 = 0.26 Waist circumference, cm −0.01 0.26 0.0005 Laboratory model: R2 = 0.46 Visceral adiposity area, cm2 −0.002 0.28 0.005 Thigh intermuscular adiposity area, cm2 −0.02 0.12 0.02 IL-6, log pg/ml −0.22 0.07 0.07 -
Multivariable modeling was performed using linear models with backward stepwise variable selection. For the clinical model, variable inclusion was based on conceptual hypotheses regarding traditional risk factors and disease-associated factors affecting insulin sensitivity index and included age, sex, waist circumference, physical activity, disease activity (28 joints), disease-modifying agent use, biologic use, and prednisone use. Based on results from bivariate analyses, for the laboratory model, waist circumference was replaced with visceral adiposity and thigh intermuscular adiposity, and disease activity was replaced with interleukin (IL)-6; all other variables from the clinical model were included.
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