Table 1

Baseline characteristics of cases and controls

CasesControls
Number19479735
Age in years, median (IQR)*74 (70–79)74 (70–79)
Sex (% women)*66.166.1
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 (%)52.546.7
DMARD prescription within past 45 days (%)
Methotrexate30.127.5
Sulfasalazine1.82.1
Leflunomide0.60.3
Chloroquine/hydroxychloroquine20.921.6
Azathioprine2.81.5
Cyclophosphamide2.30.5
Anti-TNF therapy0.30.1
Gold4.85.5
Others (ciclosporin, mycophenolate mofetil, D-penicillamine)1.11.0
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)26.515.7
Osteoporosis24.817.5
Chronic renal disease0.40.1
Cancer4.31.7
Diabetes8.46.0
PPI/H2 blocker prescription within past 45 days (%)36.624.1
  • * 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.