- Previous reports have shown a possible association between psoriasis and obesity, ischaemic heart disease, hypertension or diabetes mellitus. However, most of these studies were uncontrolled and were based on small sample sizes. We therefore investigated the association between psoriasis and the metabolic syndrome in a case control study. Case patients were defined as patients with a diagnosis of psoriasis vulgaris. Control patients were subjects who underwent hernioplasty or appendectomy. We used data mining techniques utilizing the database of the southern district of Clalit Health Services. The proportions of patients with diseases that belong to the metabolic syndrome were compared between case and control patients by univariate analyses. chi2 tests were used to compare categorical parameters between the groups. Logistic regression models were used to measure the association between psoriasis and the metabolic syndrome. A total of 340 patients with psoriasis and 6643 controls were included in the study. The mean age of case patients was 47.7 years (SD 10.7 years). There were 50.3% men and 49.7% women. Ischaemic heart disease was present in 23.5% of the patients with psoriasis, compared with 17.2% of the controls (p=0.003). Diabetes mellitus was present in 27.9% of the patients with psoriasis, compared with 19.5% of the controls (p <0.001). Hypertension was present in 44.4% of the patients with psoriasis, compared with 37.2% of the controls (p=0.007). Obesity was present in 29.4% of the patients with psoriasis, compared with 23.5% of the controls (p=0.012). Dyslipidaemia was present in 50.9% of the patients with psoriasis, compared with 44.2% of the controls (p=0.015). The association between psoriasis and the metabolic syndrome was pronounced after the age of 50 years and in men. Multivariate models adjusting for age and gender demonstrated that psoriasis was associated with an increased risk for ischaemic heart disease (odds ratio (OR) 1.4 95% confidence interval (CI) 1.0-1.8), diabetes mellitus (OR 1.5 95% CI 1.2-2.0), hypertension (OR 1.3 95% CI 1.0-1.7), obesity (OR 1.3 95% CI 1.0-1.7) and dyslipidaemia (OR 1.2 95% CI 1.0-1.6). Our findings demonstrate a possible association between psoriasis and the metabolic syndrome. Further studies are needed to establish this observation.