Table 1.
Characteristics of patients with rheumatoid arthritis (RA) and control subjects
| Characteristics | RA patients (n=166) | Control (n=92) | P-value* |
|---|---|---|---|
| Age (years) | 54 (45 – 63) | 53 (45 - 60) | 0.43 |
| Female sex – n (%) | 114 (68.7) | 58 (63.0) | 0.41 |
| Race – White (%) | 147 (88.6) | 78 (84.8) | 0.44 |
| Education level | |||
| High school or less – n (%) | 80 (48.5) | 26 (28.3) | 0.002 |
| College level or more – n (%) | 85 (51.5) | 66 (71.7) | 0.002 |
| Body mass index – kg/m2 | 28.4 (24.0 – 33.2) | 27.0 (24.5 – 31.2) | 0.43 |
| Weight – kg | 79.0 (70.2 – 91.2) | 76.5 (69 - 92.4) | 0.56 |
| Height – m | 1.7 (1.6 -1.8) | 1.7 (1.6-1.8) | 0.74 |
| Currently smoking | 39 (23.5) | 8 (8.7) | 0.004 |
| Insulin resistance – HOMA-IR index$ | 84 (51.9) | 16 (17.8) | <0.001 |
| Metabolic syndrome – n (%)$ | 59 (37.1) | 19 (21.8) | 0.02 |
| Diabetes mellitus – n (%) | 19 (11.4) | 4 (4.3) | 0.07 |
| Serum creatinine – mg/dl | 0.8 (0.7-0.9) | 0.8 (0.7 - 0.9) | 0.62 |
| GFR – ml/min per 1.73 m2 | 87.3 (73.7 – 102.7) | 84.8 (76.3 – 94.3) | 0.40 |
| Duration of disease - years | 3.5 (2 – 18) | N/A | N/A |
| DAS28 score | 3.9 (2.6-4.8) | N/A | N/A |
| Hypertension (%) | 54.0 | 39.0 | 0.03 |
| Systolic blood pressure (mm Hg) | 134 (119 – 146) | 129 (115 – 137) | 0.05 |
| Diastolic blood pressure (mm Hg) | 75 (68 – 82) | 72 (68 – 78) | 0.08 |
| Anti-hypertensive use (%) | 38.6 | 26.4 | 0.06 |
| Diuretic use (%) | 30 (18.1%) | 9 (9.8%) | |
| Non steroidal anti inflammatory drugs use (%) | 51 (30.7) | 9 (9.9) | |
| Estimated 24 hour urinary Na (grams), median (IQR) | 5.1 (3.9 – 6.6) | 4.9 (4.1 – 6.5) | 0.9 |
| Estimated 24 hour urinary potassium (grams), median (IQR) | 2.5 (2.1-3.2) | 2.7 (2.3 – 3.8) | 0.08 |
| Estimated 24 hour urinary Na:K ratio | 2.0 (1.6 – 2.4) | 1.7 (1.5 -2.1) | 0.02 |
Continuous variables are presented as median (interquartile range)
$
Data to calculate the HOMA (Homeostasis Model Assessment) index was available in 160 patients with RA and 90 control subjects. A HOMA index of >2.114 was used as a cut-off point of insulin resistance.17
Data to calculate the metabolic syndrome was available in 159 patients with RA and 87 control subjects
*
P-values represent the comparison between RA patients and controls by Mann-Whitney test and Fisher’s exact test, as appropriate.
**
1 mmol sodium = 23 mg sodium