Prevalence and Incidence of Psoriatic Arthritis among Patients with Psoriasis and Risk Factors for Psoriatic Arthritis in Republic of Korea: A Nationwide Database Cohort Study.

Population-based epidemiological studies on disease burden and risk factors for psoriatic arthritis (PsA) in patients with psoriasis (PsO) are limited, especially in Asian populations. Therefore, the aim was to determine the prevalence and incidence of PsA among PsO patients in Korea, and examine associated clinical factors. A cohort study was performed to determine the annual prevalence and incidence of PsA among PsO patients between 2008 and 2020 using nationwide claims data in Korea. Risk factors for PsA development were also examined using logistic regression among matched PsA cases and controls. An increasing trend in PsA prevalence per 1,000 patients was observed; prevalence was 6.17 (95% confidence interval [CI] 5.73-6.65) in 2008 and 19.03 (95% CI 18.39-19.70) in 2020. Similarly, the PsA incidence rate per 1,000 patient-years increased from 3.35 (95% CI 3.01-3.72) in 2008 to 5.01 (95% CI 4.68-5.36) in 2020. Patients with plaque PsO, moderate-to severe PsO, receiving oral systemic therapy or phototherapy, with a higher burden of comorbidities, and concomitant autoimmune diseases had a higher risk of PsA. The results provide insight into the burden of PsA among PsO patients in Korea and risk factors associated with developing PsA.