Cigarette smoking influences the clinical severity of psoriasis, according to a study in the December issue of Archives of Dermatology. Investigators at the Istituto di Ricovero e Cura a Carattere Scientifico in Rome analyzed data from 818 adults with psoriasis in a large cross-sectional study performed between 2000 and 2002 in inpatient wards of a hospital for skin diseases in Rome, the Istituto Dermopatico dell'Immacolata Multipurpose Psoriasis Research on Vital Experiences (IMPROVE) study.
They found that smoking more than 20 cigarettes per day doubled the risk of clinically more severe psoriasis, compared with smoking 10 cigarettes or fewer each day. This risk calculation accounted for potential confounding factors, such as sex, age, body mass index, psychological distress, family history of psoriasis, duration of psoriasis disease, and alcohol consumption. In addition, cigarette-years, measured as the product of the intensity and duration of smoking in years, was associated with a 30 percent increased risk of more severe psoriasis for a 600-U increase, which corresponds, for example, to 20 cigarettes per day for 30 years.
Smoking had a much stronger effect on psoriasis in women than in men, according to the researchers. In women, average current and recent former smokers had a 72 percent higher risk of more severe psoriasis than those who had never smoked. The effect of cigarette-years also was stronger in women than men.