Results for final multivariate linear mixed model of fatigue (modified Fatigue Severity Scale) on laboratory, clinical, and patient-reported measures of disease activity and function in the context of comorbidity, medication status, age, sex, and arthritis duration.
| Variable | Estimate | SE | t value | p |
|---|---|---|---|---|
| Intercept | 6.6269 | 0.4546 | 14.578 | < 0.0001 |
| Sex (male vs female) | −0.0588 | 0.1769 | −0.332 | 0.740 |
| Age | −0.0085 | 0.0076 | −1.111 | 0.267 |
| Arthritis duration | −0.0015 | 0.0101 | −0.149 | 0.882 |
| Morning stiffness (yes vs no) | 0.1891 | 0.1115 | 1.696 | 0.090 |
| HAQ | 1.2923 | 0.1557 | 8.300 | < 0.0001 |
| SF-36 pain scale | −0.0189 | 0.0026 | −7.380 | < 0.0001 |
| SF-36 mental health scale | −0.0275 | 0.0027 | −10.152 | < 0.0001 |
| Diagnosis of fibromyalgia (yes vs no) | 0.8161 | 0.3625 | 2.251 | 0.024 |
| Ever had hypertension (yes vs no) | 0.3007 | 0.1356 | 2.218 | 0.027 |
| Ever used methotrexate (yes vs no) | 0.3836 | 0.1341 | 2.859 | 0.004 |
| Interaction of arthritis duration with fibromyalgia | 0.0386 | 0.0156 | 2.474 | 0.0133 |
| Interaction of morning stiffness with fibromyalgia | 0.4243 | 0.1999 | 2.123 | 0.034 |
| Interaction of HAQ with fibromyalgia | −0.6954 | 0.2176 | −3.196 | 0.001 |
| Variance components | Variance | SD | ||
| Between patients | 2.0811 | 1.4426 | ||
| Within patient | 1.5054 | 1.2270 | ||
| No. of records | 1534 | |||
| No. of patients with 2 or more visits | 385 |
HAQ: Health Assessment Questionnaire; SF-36: Medical Outcomes Study Short Form-36.