Baseline characteristics of cases and matched controls from a base population of 16 207 RA patients, 1985–2003
| Cases | Controls* | |
|---|---|---|
| Number | 13 634 | 68 170 |
| Age (years, mean (SD)) | 71.9 (6.0) | 71.8 (5.9) |
| Sex (% women) | 68.9 | 68.9 |
| Follow-up (years, mean (SD)) | 1.2 (1.5) | 1.2 (1.5) |
| Number of rheumatologist visits in 6 months before index date (mean (SD)) | 1.5 (2.7) | 1.4 (2.5) |
| NSAID prescription within last 45 days | 55.2 | 55.7 |
| Extra-articular RA | 0.2 | 0.1 |
| DMARD prescription within past 45 days† | ||
| Methotrexate | 33.3 | 33.0 |
| Sulfasalazine | 2.4 | 3.0 |
| Leflunomide | 0.3 | 0.3 |
| Chloroquine/hydroxychloroquine | 29.4 | 30.7 |
| Azathioprine | 1.9 | 1.5 |
| Cyclophosphamide | 1.7 | 0.7 |
| Anti-TNF therapy | 0.1 | 0.1 |
| Gold | 7.1 | 6.5 |
| Others (ciclosporin, mycophenolate mofetil, d-penicillamine) | 1.8 | 1.7 |
| No of hospital admissions in year preceding index date (mean (SD)) | 0.5 (1.0) | 0.4 (0.8) |
| No of GP visits in year preceding index date (mean (SD)) | 7.8 (9.0) | 6.1 (7.7) |
| No of hospital specialist visits (excluding rheumatologist) in year preceding index date (mean (SD)) | 9.9 (13.1) | 7.6 (10.8) |
| Comorbidity (from ICD-9 or drug codes) | ||
| Diabetes | 9.3 | 7.8 |
| Chronic respiratory disease (COPD/asthma/ILD) | 20.3 | 12.1 |
| Osteoporosis | 17.9 | 15.6 |
| Chronic renal disease | 20.3 | 12.1 |
| Cancer | 4.3 | 2.7 |
| PPI/H2 blocker prescription within last 45 days | 27.9 | 20.0 |
Numbers are percentages unless otherwise stated.
↵* Each patient within the cohort could contribute more than once to the controls.
↵† Patients could receive combination disease-modifying antirheumatic drug (DMARD) therapy and contribute to more than one drug category.
COPD, chronic obstructive pulmonary disease; GP, general practitioner; ICD, International Classification of Diseases; ILD, interstitial lung disease; NSAID, non-steroidal anti-inflammatory drug; PPI, proton pump inhibitor; RA, rheumatoid arthritis.