Smoking, but not alcohol, is associated with risk of psoriasis in a Taiwanese population-based cohort study

Background: Alcohol consumption and smoking have long been suspected of increasing the risk of developing psoriasis. Most evidence to date has derived from cross-sectional or case-control studies. Objective: We sought to investigate the effects of alcohol and smoking on incident psoriasis. Methods: Alcohol consumption, smoking status, and other covariates were collected from four rounds (2001, 2005, 2009, and 2013) of the Taiwan National Health Interview Survey. Incident psoriasis was identified from the National Health Insurance database. Cox regression model was used for the analysis. Results: Of 60,136 subjects, 242 (0.40%) developed psoriasis. After controlling for demographics and comorbidities, alcohol consumption was not significantly associated with psoriasis risk. Conversely, psoriasis risk was higher for current smokers than never smokers (adjusted hazard ratio 1.47 [95% confidence interval 1.04-2.07]). The risks were higher among subjects who smoked >25 cigarettes per day and for >20 pack-years. In subgroup analysis, current smoking was significantly associated with risk of psoriasis without psoriatic arthritis but not psoriatic arthritis alone. Limitations: Alcohol consumption was not assessed based on the number of drinks consumed. Conclusion: Current smoking increased the risk of psoriasis, particularly augmented for individuals who smoked >25 cigarettes per day and for >20 pack-years, while alcohol consumption was not significantly associated with psoriasis development.