Comparison of characteristics of cases and controls of the NCC study. Data are n (%) unless otherwise specified.
| Characteristics | Case group, n = 43 | Control group, n = 214## | p |
|---|---|---|---|
| Median age*, yrs (IQR) | 64.0 (57.0–72.0) | 63.5 (56.0–71.0) | — |
| Female | 37 (86.0) | 184 (86.0) | — |
| Observation start year after 2008# | 15 (34.9) | 74 (34.6) | — |
| Median disease duration, yrs# (IQR) | 8.0 (2.0–15.0) | 7.0 (2.3–14.1) | 0.674 |
| Steinbrocker class 3 or 4# | 12 (27.9) | 77 (36.0) | 0.310 |
| Steinbrocker stage III or IV# | 26 (60.5) | 113 (52.8) | 0.358 |
| Median DAS28 3/CRP# (IQR) | 4.4 (3.6–5.6), n = 39 | 4.2 (3.3–5.2), n = 173 | 0.169 |
| Any comorbidity# | 29 (67.4) | 132 (61.7) | 0.476 |
| Pulmonary disease, renal failure, or diabetes mellitus | 14 (32.6) | 69 (32.2) | — |
| Pulmonary disease | 13 (30.2) | 65 (30.4) | 0.985 |
| Liver disease | 1 (2.3) | 6 (2.8) | 0.668 |
| Renal failure | 1 (2.3) | 7 (3.3) | 0.602 |
| Diabetes mellitus | 5 (11.6) | 26 (12.1) | 0.924 |
| Malignancies | 1 (2.3) | 1 (0.5) | 0.307 |
| Autoimmune disease other than RA | 7 (16.3) | 19 (8.9) | 0.119 |
| Others | 17 (39.5) | 79 (36.9) | 0.746 |
| Use of biological DMARD* | 34 (79.1) | 133 (62.1) | 0.034 |
| TNFi | 30 (69.8) | 110 (51.4) | 0.027 |
| Infliximab | 7 (16.3) | 40 (18.7) | 0.709 |
| Adalimumab | 4 (9.3) | 15 (7.0) | 0.396 |
| Etanercept | 19 (44.2) | 55 (25.7) | 0.015 |
| Non-TNFi | 4 (9.3) | 23 (10.7) | 0.516 |
| Tocilizumab | 4 (9.3) | 21 (9.8) | 0.590 |
| Abatacept | 0 (0.0) | 2 (0.9) | 0.693 |
| Use of immunosuppressive DMARD*^ | 5 (11.6) | 31 (14.5) | 0.622 |
| Use of MTX* | 23 (53.5) | 133 (62.1) | 0.289 |
| Median dosage of MTX, mg/week (IQR) | 8.0 (8.0–10.0) | 8.0 (6.0–8.0) | 0.002 |
| MTX > 8 mg/week | 8 (18.6) | 23 (10.7) | 0.149 |
| Use of oral corticosteroids* | 27 (62.8) | 120 (56.1) | 0.417 |
| Median dosage of PSL**, mg/day (IQR) | 5.0 (3.0–10.0) | 5.0 (3.0–5.8) | 0.153 |
| PSL ≥ 5 mg/day** | 15 (34.9) | 65 (30.4) | 0.560 |
↵* Data on age and oral corticosteroids use were recorded at index date; biological DMARD use during the 90 days preceding the index date; immunosuppressive DMARD use at the index date; and methotrexate use during the 7 days preceding the index date.
↵# Data were collected at baseline on the observation start year, disease duration, Steinbrocker class, Steinbrocker stage, DAS28 3/CRP, and comorbidity.
↵^ Immunosuppressive DMARD include tacrolimus, leflunomide, mizoribine, azathioprine, and cyclophosphamide.
↵** The oral corticosteroids dosage was converted to the equivalent prednisolone dosage.
↵## One case had only 4 matched controls. Steinbrocker classification26 was used to define RA disease stages and classes. IQR: interquartile range; DAS28 3/CRP: Disease Activity Score including 28-joint count and C-reactive protein; RA: rheumatoid arthritis; DMARD: disease-modifying antirheumatic drugs; MTX: methotrexate; PSL: prednisolone; NCC: nested case control.