To determine whether patients with rheumatoid arthritis (RA) are at increased risk of hospitalized infection and whether the risk varies by RA treatment.
A retrospective cohort study was conducted using data from a medical and pharmacy claims managed-care database from 1999 to 2006. A total of 24,530 patients were included in the RA cohort; a random sample of non-RA patients served as a comparison cohort (n = 500,000). Rates of hospitalized infection were compared between the cohorts. A nested case-control analysis was performed within the RA cohort to assess the effect of current RA medication use on hospitalized infection risk.
A total of 1,993 patients with RA and 11,977 non-RA patients experienced a hospitalized infection. The rate of first hospitalized infection was higher in the RA cohort [adjusted hazard ratio = 2.03; 95% confidence interval (CI) 1.93-2.13]. In the case-control analysis, the current use of biological disease modifying antirheumatic drugs (DMARD) was associated with slightly increased risk of hospitalized infection [rate ratio (RR) = 1.21; 95% CI 1.02-1.43]. Methotrexate and hydroxychloroquine were associated with decreased risk. Oral corticosteroid use increased risk (RR = 1.92; 95% CI 1.67-2.21), and there was a dose-related effect [< or = 5 mg/day: RR = 1.32 (95% CI 1.06-1.63), 6-10 mg/day: RR = 1.94 (95% CI 1.53-2.46), > 10 mg/day: RR = 2.98 (95% CI 2.41-3.69)].
These data confirm that individuals with RA are at increased risk of hospitalized infection compared to those without RA. Oral corticosteroid use was associated with a dose-related increase. Biological DMARD use was associated with slightly elevated risk; however, this may reflect confounding and channeling bias.