Although cardiovascular risk in patients with mild psoriasis may be relatively small, it increases with severity of disease1. However, in the absence of robust measurements, studies to date relied mostly on treatment spectrum as a proxy for disease severity. Usually, the subjects were defined as having moderate to severe psoriasis if they had a history of systemic treatments. However, some psoriasis therapies may increase incidence of cardiovascular diseases while others may decrease it12. These heterogenous effects of individual drugs on cardiovascular disease may limit current practice of determining the severity according to past treatment history, in the aspect of evaluating the current cardiovascular risk factors. Then we used psoriasis area and severity index (PASI) which is widely used to measure severity in both research and clinical setting as a severity index. To date, few studies which determine the relationship between cardiovascular risk factors and PASI have been published and the relationship has not been clearly demonstrated in Asian psoriasis patients.

The recent literature has focused on linking psoriasis severity with an increase in comorbidity risk, a risk evident even with mild psoriasis compared with controls4. Through meta-analysis, it was found that patients with severe psoriasis may have an even higher risk of developing diabetes5. In addition, ischemic heart disease and cardiovascular risk factors were associated with psoriasis in hospitalized patients, who were hypothesized to be severe psoriasis patients6. It has been also speculated that the more severe psoriasis is, the greater the incidence of metabolic syndrome7. In Korean studies, there were conflicting results in respect of incidence of metabolic syndrome. Kim et al.8 reported that there was no significant difference in prevalence of metabolic syndrome in regard to the body surface area, well known risk factor for severe psoriasis. In the contrary, Choi et al.9 showed the risk of metabolic syndrome was associated with the severity of psoriasis determined by whether history of systemic treatments exist or not.

To our knowledge, there were only few reports which analyzed how cardiovascular comorbidities were affected by PASI. In a Canadian study consisting of psoriatic arthritis patients, risk of hypertension correlated positively with high PASI score, and the risk of myocardial infarction was proven to be more prominent in the group with PASI score greater than 2010. Also, it was reported Framingham risk score, one of the widely used cardiovascular risk score estimation system, showed the significant correlation with PASI, but not with body surface area, characteristics of treatment, duration of psoriasis in a Spanish study11. On the other hand, there was no difference in the prevalence of metabolic syndrome between patients with PASI score lower and higher than 10 in an Italian study12.

To assess the severity of psoriasis for determining the relationship to cardiovascular risk factors, we concluded classifying severity based on the medication history was inappropriate, because the opinions of the patients may affect treatment intensity or schedule, and systemic medications itself may influence cardiovascular risk factors. It is well known that systemic psoriasis therapies affect the risk of cardiovascular disease. Acitretin can increase serum triglycerides and cholesterol, specifically by shifting high-density lipoproteins to low-density lipoproteins. Cyclosporine can increase blood pressure, serum triglycerides, and total cholesterol. On the other hand, methotrexate and tumor necrosis factor inhibitors may reduce the risk of cardiovascular disease morbidity1. Psoriasis treatments work by anti-inflammatory mechanism and thus it could be hypothesized that decrease of inflammation with psoriasis treatments may lead to improvement of cardiovascular risk2.

In the present study, significant differences of cardiovascular risk factors and lipid profile according to the severity of the psoriasis were not discovered except in triglyceride level. Prevalence of DM was shown to be higher in psoriasis groups as a whole compared to control group, but between in regard to severity the mild group had more DM patients than the moderate-and-severe group with significant results. In previous studies813, it was described that only triglyceride level exhibited significant difference between psoriasis and control subjects among lipid profile; HDL, LDL, and total cholesterol were not subject to same conclusion. The reason why the only triglyceride level resulted in this abnormality remains unclear. We think that careful attention must be paid to dyslipidemia—hypertriglyceridemia in particular—in psoriasis patients, especially if the degree of psoriasis is moderate to severe. Similar lipid profile between both groups—again excluding triglyceride level—might be due to inadequate sample size or other circumstance such as administration of antihypertensive or antidiabetic agent, as these are known to affect lipid metabolism in various ways; antihypertensive medication such as β-blocker or thiazide diuretics are known to have deleterious effect to lipid metabolism, while calcium channel blockers and angiotensin-converting enzyme inhibitors are found to have favorable effect14.

Thiazolidinediones can cause an elevation in HDL and variable increase in LDL, while metformin and insulin have favorable effects by decreasing triglycerides and raising HDL15. Triglyceride levels and the coefficient of both group were respectively 0.143 (p=0.098), 0.248 (p=0.006), which showed positive correlation, and significance was observed in moderate to severe group. This is supposedly because the more severe psoriasis is, the more patient went through systemic therapy and, oral medications such as acitretin, cyclosporine could have increased serum triglyceride level. As the sample size was relatively small, further study with bigger sample size is needed.

After matching age and gender, incidences of hypertension in psoriasis patients group in our study were not significantly higher than control group, and that of hypertension and DM showed inverse correlation with severity of the disease—in addition, the result of DM was significant. Because we analyzed the presence of these diseases only through questionnaire survey, it is possible some cases were unnoticed, causing underestimation of the prevalence among subjects. Relatively small sample size may have contributed the confounding of results, too. These limitation of our study mentioned above calls for further investigation to elucidate the exact nature of association. Larger study such as nationwide studies are needed to prove or disprove the association between the severity of psoriasis and cardiovascular risk factors in Korean psoriasis patients.