Investigating the epidemiological relationship between vitiligo and psoriasis: a population-based study

Background The association of vitiligo with psoriasis is inconsistent in the current literature. Objective To assess the bidirectional association between vitiligo and psoriasis. Methods A population-based study was performed to compare vitiligo patients (n = 20,851) with age-, sex- and ethnicity-matched control subjects (n = 102,475) regarding the incidence of new-onset and the prevalence of preexisting psoriasis. Adjusted hazard ratios (HRs) and adjusted odds ratios (ORs) were calculated by cox regression and logistic regression, respectively. Results The incidence rate of new-onset psoriasis was estimated at 7.9 (95% CI 6.4-9.7) and 4.7 (95% CI 4.1-5.3) cases per 10,000 person-years among patients with vitiligo and controls, respectively. Patients with vitiligo experienced an increased risk of psoriasis (fully-adjusted HR 1.71; 95% CI 1.35-2.17; P < 0.001). On the other hand, the odds of vitiligo were only marginally elevated among patients with preexisting psoriasis (fully-adjusted OR 1.19; 95% CI 1.01-1.40; P = 0.051). Compared to other patients with vitiligo, those with vitiligo and comorbid psoriasis were older at the onset of the disease and had a greater prevalence of metabolic and cardiovascular comorbidities. Conclusions A diagnosis of vitiligo predisposes individuals to develop subsequent psoriasis. Clinicians managing dermatologic patients ought to be aware of this comorbidity. Further research is required to explicate the pathomechanism underlying this epidemiological observation.