To estimate incidence rate (IR) and risk factors for opportunistic infections (OI) in early rheumatoid arthritis (RA) patients.
Retrospective cohorts were identified in the Korean National Claims Database. Incident RA cases were recruited in 2010 (n = 14 081). Follow up was ended at the time of development of new OI or at the date of last visit within 12 months of diagnosis. The IR and standardized incidence ratio (SIR) of OI in early and overall RA (n = 226 838) over a year were calculated. A multivariable regression model was used to identify risk factors for OI in early RA.
The IR of OI in early and overall RA were 3.81/100 and 3.67/100 person-years, respectively. The SIR for OI in early RA was 1.14 (95% CI, 1.05-1.23). Herpes zoster (SIR = 1.12, 95% CI, 1.03-1.22) and candidiasis (SIR = 2.40, 95% CI, 1.55-3.54) were common in early RA. Age (50 < age ≤ 60 [OR 1.74, 95% CI, 1.30-2.33], 60 < age ≤ 70 [OR 1.85, 95% CI, 1.36-2.52], age > 70 [OR 1.89, 95% CI, 1.34-2.68]), female sex (OR 1.40, 95% CI, 1.12-1.74), comorbidities (one comorbidity [OR 1.53, 95% CI, 1.24-1.89], ≥ two comorbidities [OR 1.84, 95% CI, 1.47-2.29]), and corticosteroid use of 5 mg/d or more (OR 1.38, 95% CI, 1.13-1.69) were significantly associated with increased risk of OI in early RA.
Opportunistic infections, especially for herpes zoster and candidiasis, tend to occur more often in early RA than in overall RA. Age, female sex, comorbidities and corticosteroid use are related to increased OI in early RA patients.