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The influence of systemic glucocorticoid therapy upon the risk of non-serious infection in older patients with rheumatoid arthritis: a nested case–control study
  1. W G Dixon1,2,
  2. A Kezouh2,
  3. S Bernatsky3,
  4. S Suissa2
  1. 1Arthritis Research UK Epidemiology Unit, Manchester Academic Health Science Centre,The University of Manchester, Manchester, UK
  2. 2Centre for Clinical Epidemiology, Lady Davis Institute – Jewish General Hospital, McGill University, Montreal, Canada
  3. 3Division of Clinical Epidemiology, McGill University Health Centre, Montreal, Canada
  1. Correspondence to Dr W G Dixon, Arthritis Research UK Epidemiology Unit, The University of Manchester, Stopford Building, Oxford Road, Manchester M13 9PT, UK; will.dixon{at}manchester.ac.uk

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).

Conclusion 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.

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Footnotes

  • Funding WGD was partly supported by a travel award from the Dickinson Trust Scholarship Fund, Central Manchester Foundation Trust. The database acquisition was funded by a grant to SS from the Canadian Institutes of Health Research (CIHR) and the Canadian Foundation for Innovation (CFI).

  • Ethics approval This study was conducted with the approval of the McGill University Institutional Review Board.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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