describes the demographics of the study population. At the end of the survey collection period 4,634 of 4,900 provider-based surveys were completed giving a response rate of 95%. Our cohort included 4,065 people with confirmed psoriasis and 40650 matched controls. The mean age of psoriasis patients was 1.2 years older than controls (p<0.001) and 51% of psoriasis patients were male compared to 48% of controls (p<0.001). 2,044 (53%) participants had mild psoriasis (≤2% body surface area (BSA)), 1,377 (35%) had moderate disease (3-10% BSA), and 475 (12%) had severe psoriasis (>10% BSA). Information on body mass index, blood pressure, HDL, glucose and triglycerides was available for 41,249 (92%), 44,019 (98%), 25234 (56%), 26,144 (64%) and 25,067 (56%) of patients, respectively (). The availability of these variables was similar in patients with and without psoriasis.
Demographic details of cohort
Metabolic syndrome was identified in 34% of participants with psoriasis compared to 26% of controls, odds ratio (OR) 1.50 (95% confidence interval (CI) 1.40-1.61). This association persisted after adjusting for age, gender and follow up, adjusted (adj.) OR 1.41 (95% CI 1.31-1.51). Adjusting for smoking and social class did not change study findings and these were not retained in the final model. Psoriasis severity affected the degree of association, with metabolic syndrome seen in 32% with mild disease (adj. OR 1.22, 95% CI 1.11-1.35), 36% with moderate disease (adj. OR 1.56, 95% CI 1.38-1.76) and 40% of those with severe psoriasis (adj. OR 1.98, 95% CI 1.62-2.43). Modest but statistically significant interactions were detected between psoriasis and age and between psoriasis and sex whereby the odds ratio of metabolic syndrome and psoriasis was slightly higher in younger age groups and in women (data not shown).
Studying the components of metabolic syndrome, the following factors were more common in psoriasis patients than in controls: obesity in 38% vs. 31% (OR 1.38, 95% CI 1.29-1.48), raised triglycerides in 36% vs. 28% (OR 1.49, 95% CI 1.39-1.60), diagnosed hypertension in 31% vs. 28% (OR 1.20, 95% CI 1.11-12.9) and raised glucose in 22% vs. 16% (OR 1.44, 95% CI 1.33-1.56) ().
In the fully adjusted model to understand which components of the metabolic syndrome were associated with psoriasis after adjusting for other elements of metabolic syndrome and age, gender and duration of follow up, the strongest association between a component of the metabolic syndrome and psoriasis was with obesity, adj. OR 1.25 (95% CI 1.16-1.34). The association with obesity demonstrated a dose-response with a 14% increase in obesity with mild psoriasis, adj. OR 1.14 (95% CI 1.03-1.27), 34% increase in obesity with moderate psoriasis, adj. OR 1.34 (95% CI 1.18-1.53), increasing to a 66% increased odds of being obese in those with severe psoriasis, adj. OR 1.66 (95% CI 1.33-2.07) (). Hypertriglyceridemia and hyperglycemia showed similar dose-response relationships with severity of psoriasis. There was a 20% increased odds of having raised triglycerides in individuals with psoriasis overall independent of obesity, adj. OR 1.20 (95% CI 1.10-1.31). This association also demonstrated an increase from mild psoriasis where the odds of raised triglycerides was 10% (adj. OR 1.10, 95% CI 0.98-1.25) to a 46% increase in those with severe psoriasis, adj. OR 1.46 (95% CI 1.13-1.88). Raised glucose was also associated with psoriasis independent of obesity, with a 16% increased odds of raised glucose overall, adj. OR 1.16 (95% CI 1.06-1.27) with the association strongest in the group with the most extensive disease ().
Association between psoriasis severity and the components of metabolic syndrome independent of other components
Sensitivity analysis using revised ATP III, International Diabetes Federation (IDF) criteria or limiting lab values to the first or most recent observation and excluding individuals on psoriasis treatments known to impact components of metabolic syndrome, e.g. ciclosporin or acitretin did not significantly change study conclusions (data not shown).