title: The influence of systemic glucocorticoid therapy upon the risk of non-serious infection in older patients with rheumatoid arthritis: a nested case-control study.
abstract: BACKGROUND
  Glucocorticoid therapy is strongly associated with an elevated risk of serious infections in patients with rheumatoid arthritis (RA). The association between glucocorticoids and common non-serious infections (NSI) is not well studied.
  
  
  METHODS
  A cohort of 16 207 patients with RA aged over 65 years was assembled using administrative data from Quebec. Glucocorticoid and disease-modifying antirheumatic drug (DMARD) therapy were identified from drug dispensing records. NSI cases were defined as first occurrence of a community physician billing code for infection or community-dispensed anti-infectives. A nested case-control analysis was performed considering drugs dispensed within 45 days of the index date, adjusting for age, sex, markers of disease severity, DMARD and comorbidity.
  
  
  RESULTS
  For 13 634 subjects, a NSI occurred during 28 695 person-years of follow-up, generating an incidence rate of 47.5/100 person-years. The crude rate of NSI in glucocorticoid-exposed and unexposed person time was 52.4 and 38.8/100 person-years, respectively. Glucocorticoid therapy was associated with an adjusted RR of 1.20 (95% CI 1.15 to 1.25). A dose response was seen, the adjusted RR increasing from 1.10 (<5 mg prednisolone/day) to 1.85 for doses greater than 20 mg/day. All glucocorticoid risk estimates (including <5 mg/day) were higher than that seen for methotrexate (adjusted RR 1.00; 0.95 to 1.04).
  
  
  CONCLUSIONS
  Glucocorticoid therapy is associated with an increased risk of NSI. The magnitude of risk increases with dose, and is higher than that seen with methotrexate, although residual confounding may exist. While the RR is low at 1.20, the absolute risk is high with one additional infection seen for every 13 patients treated with glucocorticoids for 1 year.
authors.affiliation: Arthritis Research UK Epidemiology Unit, The University of Manchester, Stopford Building, Oxford Road, Manchester M13 9PT, UK. will.dixon@manchester.ac.uk
authors.forename: W G
authors.initials: WG
authors.lastname: Dixon
authors.forename: A
authors.initials: A
authors.lastname: Kezouh
authors.forename: S
authors.initials: S
authors.lastname: Bernatsky
authors.forename: S
authors.initials: S
authors.lastname: Suissa
mesh_terms: D000284:Administration, Oral; D000368:Aged; D018501:Antirheumatic Agents / Q000009:adverse effects / Q000627:therapeutic use; D001172:Arthritis, Rheumatoid / Q000150:complications / Q000188:drug therapy* / Q000453:epidemiology; D016022:Case-Control Studies; D004305:Dose-Response Relationship, Drug; D005260:Female; D005938:Glucocorticoids / Q000008:administration & dosage / Q000009:adverse effects* / Q000627:therapeutic use; D006801:Humans; D007275:Injections, Intravenous; D008297:Male; D009894:Opportunistic Infections / Q000139:chemically induced* / Q000150:complications / Q000453:epidemiology; D011792:Quebec / Q000453:epidemiology; D012307:Risk Factors
chemical_list: D018501:Antirheumatic Agents; D005938:Glucocorticoids