Medical history, drug exposure and the risk of psoriasis. Evidence from an Italian case-control study.

BACKGROUND/AIMS: To evaluate the association of psoriasis with selected medical conditions and a number of drugs used before diagnosis. METHODS: Multicenter case-control study involving outpatient services of 20 general and teaching hospitals. Entry criteria for cases were a first diagnosis of psoriasis made by a dermatologist and a history of skin manifestations of no more than 2 years after the reported onset of the disease. Controls were the first eligible dermatological patients observed on randomly selected days in the same centers as cases. A total of 560 cases and 690 controls were recruited. RESULTS: The odds ratio (OR) of psoriasis was 0.8 (95% confidence interval, CI, 0.5-1.3) in hypertensive subjects, 1.1 (95% CI 0.6-2.0) in diabetics and 1.1 (95% CI 0.7-1.7) in hyperlipidemic subjects. Histamine 2 receptor antagonist exposure was negatively associated with psoriasis: OR 0.3 (95% CI 0.1-0.8). CONCLUSION: Our study rules out a strong association of psoriasis at its first ever diagnosis with common chronic conditions. The reported associations of psoriasis with relatively common conditions such as diabetes mellitus, hypertension and hyperlipidemia may represent a late effect of well-known risk factors for psoriasis such as smoking and overweight or reflect factors related to the long course of psoriasis itself.

Cigarette smoking, body mass index, and stressful life events as risk factors for psoriasis: results from an Italian case-control study.

We conducted a case-control study to analyse the association of psoriasis of recent onset with smoking habits, body mass index (BMI) and stressful life events. Cases (n=560; median age 38) were patients with a first diagnosis of psoriasis and a history of skin manifestations of no longer than two years after the reported disease onset. Patients with a new diagnosis of skin diseases other than psoriasis (n=690; median age 36) were selected as controls. The risk of psoriasis was higher in ex- and current smokers than in never-smokers, the relative risk estimates (OR) being 1.9 for ex-smokers and 1.7 for smokers. Smoking was strongly associated with pustular lesions (32 patients, OR=5.3 for smokers). The frequency of psoriasis varied significantly in relation to a family history of psoriasis in first degree relatives, BMI (OR=1.6 and 1.9 for over weighted, BMI 26-29, and obese, BMI >/= 30, respectively) and stressful life event score (compared to the lower index quartile, the OR being 2.2 for index values >/=115). Risk estimates, when taking into consideration the combined effect of these factors with smoking habits, were consistent with a multiplicative model of risk combination with no significant statistical interaction.