Background: This study investigated whether patients with a history of human papillomavirus (HPV) infection are at increased risk of developing psoriasis. Methods: We enrolled 66 274 patients with HPV infection between 1997 and 2013 from the Taiwan National Health Insurance Research Database, and compared them with control individuals who had never been diagnosed with HPV infection (at a 1:4 ratio matched by age, sex and index year) in relation to the risk of developing psoriasis. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs), with the control group as reference. Results: The adjusted hazard ratio (aHR) was 1.177 (95% CI, 1.010-1.373) after adjusting for demographic characteristics, comorbidities, dermatology-related outpatient visits and medications. The HPV group had an increased risk of psoriasis compared with the control group in all of the different age groups. The P-value for interaction between age and exposure of HPV is 0.009 in our sub-group analysis. Conclusions: A higher risk of psoriasis was found after HPV infection, and age acted as an effect modifier between the HPV infection and risk of psoriasis.
