Relationship between smoking and the clinical severity of psoriasis.

OBJECTIVE To evaluate the association between different components of smoking history and the clinical severity of psoriasis. DESIGN A hospital-based cross-sectional study. SETTING Inpatient wards of a hospital for skin diseases in Rome, Italy. PATIENTS A total of 818 adults with psoriasis. MAIN OUTCOME MEASURE The Psoriasis Area and Severity Index was used to assess the clinical severity of psoriasis between February 21, 2000, and February 19, 2002. RESULTS After adjustment for potential confounders (sex, age, body mass index, psychological distress, family history of psoriasis, duration of psoriasis disease, and alcohol consumption), high intensity of smoking (>20 cigarettes daily) vs a lower level of consumption (< or =10 cigarettes daily) was associated with a more than 2-fold increased risk of clinically more severe psoriasis (odds ratio [OR], 2.2; 95% confidence interval [CI], 1.2-4.1). Cigarette-years, measured as the product of the intensity and duration (years) of smoking, significantly increased the risk of clinically more severe psoriasis after adjustment for confounding factors (OR,1.3; 95% CI, 1.0-1.6, for a 600-U increase in cigarette-years). Separate analyses for men and women showed that the effect of cigarette-years was stronger for women (OR, 1.8; 95% CI, 1.2-2.6, for a 400-U increase in cigarette-years) than for men (OR, 1.2; 95% CI, 0.9-1.6, for a 700-U increase in cigarette-years). CONCLUSION Smoking is associated with the clinical severity of psoriasis and highlights the importance of smoking cessation in patients with psoriasis.