Table 1.
Baseline characteristics of cases and controls
| Cases | Controls | |
|---|---|---|
| Number | 1947 | 9735 |
| Age in years, median (IQR)* | 74 (70–79) | 74 (70–79) |
| Sex (% women)* | 66.1 | 66.1 |
| Follow-up in years, median (IQR)* | 3.0 (1.2–5.8) | 3.0 (1.2–5.8) |
| No of rheumatologist visits in the 6 months before index date, median (IQR) | 0 (0–2) | 0 (0–1) |
| NSAID prescription within past 45 days (%) | 52.5 | 46.7 |
| DMARD prescription within past 45 days (%)† | ||
| Methotrexate | 30.1 | 27.5 |
| Sulfasalazine | 1.8 | 2.1 |
| Leflunomide | 0.6 | 0.3 |
| Chloroquine/hydroxychloroquine | 20.9 | 21.6 |
| Azathioprine | 2.8 | 1.5 |
| Cyclophosphamide | 2.3 | 0.5 |
| Anti-TNF therapy | 0.3 | 0.1 |
| Gold | 4.8 | 5.5 |
| Others (ciclosporin, mycophenolate mofetil, D-penicillamine) | 1.1 | 1.0 |
| No of hospital admissions in year preceding index date, median (IQR) | 0 (0–1) | 0 (0–1) |
| No of GP visits in year preceding index date, median (IQR) | 7 (3–14) | 5 (1–9) |
| No of hospital specialist visits (excluding rheumatologist) in year preceding index date, median (IQR) | 8 (3–16) | 5 (2–10) |
| Co-morbidity (from ICD-9 or drug codes) (%) | ||
| Chronic respiratory disease (COPD/asthma/ILD) | 26.5 | 15.7 |
| Osteoporosis | 24.8 | 17.5 |
| Chronic renal disease | 0.4 | 0.1 |
| Cancer | 4.3 | 1.7 |
| Diabetes | 8.4 | 6.0 |
| PPI/H2 blocker prescription within past 45 days (%) | 36.6 | 24.1 |
*
Variables used for matching.
†
Patients could be on more than one DMARD and contribute to more than one category.
COPD, chronic obstructive pulmonary disease; DMARD, disease-modifying antirheumatic drug; GP, general practitioner; ILD, interstitial lung disease; NSAID, non-steroidal anti-inflammatory drug; PPI, proton-pump inhibitor; TNF, tumour necrosis factor.