Objectives To study the association between traditional disease-modifying antirheumatic drugs (c-DMARD) or anti-TNF-α agents and herpes zoster (HZ) in patients with psoriatic arthritis (PsA).

Methods A retrospective cohort study was conducted in patients with PsA between 2002 and 2013. Patients were grouped as follows: no DMARDs (Group A); c-DMARDs (Group B); anti-TNF-α agents (Group C); anti-TNF-α agents in combination with c-DMARDs (Group D). Crude incidence rates (IR) were calculated as number of HZ episodes per 1000 patient-years. A Cox regression model was used to adjust for HZ risk factors (age, gender, steroid use, Charlson Comorbidity Index score, and previous treatment) in order to estimate their contribution to the risk of the first HZ event.

Results The study included 3128 patients, mean age 50.26±14.54 years; 46.2% male. During a period of 20 096 person-years 182 HZ events were observed. The crude IR (95% CI) of HZ in the study population was 9.06 per 1000 patient-years, and in Groups A-D 7.36 (5.41 to 9.79), 9.21 (7.5 to 11.21), 8.64 (4.84 to 14.26), 17.86 (10.91 to 27.58), respectively. In a multivariate analysis, age (HR 1.01, 95% CI 1.00 to 1.02), treatment with steroids (HR 1.08, 95% CI 1.04 to 1.13), and a combination of anti-TNF-α agents and c-DMARDs (HR 2.37, 95% CI 1.32 to 4.22) were significantly associated with HZ events.

Conclusions In our database, the risk of HZ was significantly increased with age, treatment with steroids, and combination of anti-TNF-α agents and c-DMARDs, but not with c-DMARDs or anti-TNF-α therapy alone. Time to HZ event was shorter in patients treated with anti -TNF-α agents.