BACKGROUND
Co-existing psoriasis (PsO) in patients with systemic sclerosis (SSc) has been reported. However, it is unclear whether SSc contributes as a risk factor for development of PsO.
OBJECTIVE
We aimed to assess whether SSc is associated with the risk of incident PsO.
METHODS
From the Korean National Health Insurance Service database, 4,933 patients with SSc and 24,665 age- and sex-matched controls were selected. Hazard ratios (HRs) and 95% confidence intervals (CIs) for incident PsO were estimated using multivariable Cox proportional hazard models adjusted for known risk factors of PsO. Further, we selected individuals whose health check-up data were available (2,355 patients with SSc and 11,775 age- and sex-matched controls). In this population, we further adjusted for additional risk factors of PsO using the health check-up data.
RESULTS
In the analysis of 4,933 patients with SSc and 24,665 age- and sex-matched controls, incidence rates of PsO in patients with SSc and controls were 10.26 and 3.20 per 1,000 person-years, respectively. After adjusting for risk factors of PsO, patients with SSc had a significantly higher risk of incident PsO (adjusted HR: 3.055 [95% CI: 2.597, 3.594]). Moreover, in the analysis of individuals who had health check-up data, additional risk factors of PsO were further adjusted; the result also showed that patients with SSc have a significantly higher risk of incident PsO (adjusted HR: 2.820 [95% CI: 2.207, 3.603]).
CONCLUSIONS
In this large cohort study, SSc was associated with a 3-fold higher risk of incident PsO than controls, independent of known risk factors of PsO. This observation advances our knowledge by showing that a risk relationship exists between SSc and PsO, beyond a simple co-existence between the two conditions.