The highly varied clinical manifestations of psoriasis range from small, reddish, scaly plaques to lesions that can cover a very large area of the body.1 The prevalence varies, as psoriasis is affected by climate, genetic susceptibility, and exposure to environmental antigens, among other variables.2,3 In Europe rates range from 1% to 6.5%4–6; in Spain an incidence of 14 cases per 10000 person-years has been described,4 and over half the cases are diagnosed before the age of 30 years.6

Psoriasis is categorized as an immune-mediated inflammatory disease (IMID) and cytokine dysregulation has been implicated in its pathogenesis.7–9 Both genetic and environmental factors have been shown to play roles in triggering these diseases,10 and an abnormal immune response is central to the pathogenesis of IMIDs such as psoriasis, inflammatory bowel disease (IBD), and spondyloarthritis.11,12 Patients who have any IMID are at higher risk of developing another one.12

Psoriasis tends to be associated with other conditions, among them cardiovascular diseases; obesity, metabolic syndrome, and other cardiovascular risk factors (CVRFs); tumor; fatty liver disease; and anxiety and depression.13–19

Although the exact mechanism underlying the association between psoriasis and cardiovascular disease are unknown, the humoral or cellular inflammatory mediators implicated in the development of atherosclerosis may be involved.20 The inflammatory process in psoriasis seems to be related to changes in interleukin levels and elevated tumor necrosis factor and C-reactive protein levels—signs that are often seen in patients with atherosclerosis.21–23

The AQUILES study was a 2-year prospective, noninterventional, multicenter observation of 3 independent cohorts of patients with psoriasis, spondyloarthritis, and IBD. The main purpose of the AQUILES study as a whole was to determine the prevalence of these IMIDs and the frequency of the clinical features in these cohorts. Its secondary aims were to determine 1) the incidence of the different IMIDs over the 2-year period, and 2) the prevalence and incidence rates of other concomitant diseases. The purpose of the present study was to determine the baseline characteristics and prevalence of IMIDs and other comorbidities in the cohort of patients with psoriasis enrolled from hospital dermatology clinics in Spain; CVRFs were of particular interest.

The results of this study show that a moderate percentage of patients with psoriasis also had another IMID, predominantly spondyloarthritis (14.0%) and within that group, the most common subtype was psoriatic arthritis (13.1% of the whole sample). Other IMIDs, such as IBD (1.3%) and uveitis (0.2%) were much less prevalent. However, other types of comorbid conditions, particularly CVRFs, were very common.

Psoriatic arthritis is the most frequent IMID in psoriasis patients. One systematic review of the literature found that psoriatic arthritis can affect 24% of psoriasis patients.25 The AQUILES study findings are very similar to those reported by García-Díez et al.26 after a cross-sectional study that evaluated the characteristics of patients with moderate or severe psoriasis in Spain and Portugal. The authors found that 13% of these patients had psoriatic arthritis. Although psoriatic arthritis usually develops after psoriasis, a small percentage of patients may develop it earlier or simultaneously (6% and 11%, respectively, in our study). It is therefore essential to inspect the skin of patients with arthritis. Our findings for IBD are consistent with those of other studies, which have reported relatively low prevalence rates of IBD in psoriasis patients; however, the rates are higher than in the general population, where ulcerative colitis and Crohn disease occur in around 0.3% and 0.1% to 0.2%, respectively.27,28

Nearly three quarters of the concomitant conditions found were some type of CVRF, and obese patients had higher rates of other CVRFs than normal-weight patients. These findings should be interpreted in the light of the relatively young average age of this cohort (46.7 years), in which there was a higher prevalence of CVRFs than in the 2006 national survey.29 Like our study, the 2006 survey was based on prior diagnoses and required neither blood pressure measurement or laboratory testing. Thus, while both studies suggest that the CVRF prevalence is higher in patients with psoriasis than it is in the general Spanish population, they may both have underestimated the prevalence since they were similarly based on reviews of patient records, without additional diagnostic testing. The DARIOS study (on dyslipidemia, atherosclerotic risk, elevated C-reactive protein, and inflammatory and oxidative status in Spain), which sought to determine the prevalence of CVRFs in the population between the ages of 35 and 74 years in 10 Spanish autonomous communities, did include the measurement of blood pressure, along with weight, height, and blood sugar and lipid levels.30 The CVRF rates were similar in the DARIOS study and ours, which both saw higher rates than the national survey of 2006.

We would like to highlight the relevance of our findings for dermatologists, in the context of the Spanish national survey of 2006 and the DARIOS study. Patients with psoriasis have a higher CVRF prevalence than might be expected for their age or sex. Many of these patients are young and may never have had their blood pressure taken or cardiovascular risk evaluated before they consult a dermatologist. Thus, the dermatologist may play a key role in detecting CVRFs simply by checking blood pressure and ordering basic blood tests. A recent study of 368 patients with psoriasis found that the dermatologist had detected at least 1 previously undiagnosed CVRF in 27% of these patients by simply taking these two steps.31 It is also important to bear in mind that some psoriasis treatments can affect CVRFs,32,33 and that obesity can alter the response to biologics because the effects of drugs administered at fixed doses may be attenuated in heavier patients.34

We must underline the limitations of the AQUILES study. As mentioned, data were collected by reviewing clinical records, and no blood pressure or other diagnostic tests were done; therefore the prevalence of comorbidities such as hypertension, high cholesterol levels, and diabetes may have been underestimated. Second, the sample studied was smaller than targeted, affecting the precision of the prevalence rates calculated; the sample size finally enrolled allows us to assume a precision of 3%. Third, as the patients enrolled were found through hospital clinics, the data cannot be extrapolated to the general population of patients with psoriasis. Two additional limitations affecting the interpretation of the data should also be taken into consideration. One is that the hospital clinics did not use a randomized patient selection method but rather enrolled participants consecutively, an approach that favors the inclusion of more seriously ill patients or those with more comorbidities, as such individuals are the ones who consult hospital specialists for chronic diseases. The second is that the presence of a chronic disease such as psoriasis may hasten the diagnosis of other diseases, such as axial spondyloarthritis, which is usually detected 6 to 9 years after onset of symptoms in the general population35; consulting a dermatologist can contribute to the likelihood of early diagnosis, since psoriasis usually develops at an earlier age. Within the constraints of these limitations, the AQUILES study provides a useful portrait of a typical hospital psoriasis caseload in dermatology, where there are comorbidities the specialist can help to identify early.

Based on our findings, we conclude that the prevalence of other IMIDs is moderate in patients seen for psoriasis in hospital dermatology clinics, and the main concomitant IMID is psoriatic arthritis. The prevalence of IBD is low; although it is higher than in the general population27,28 few cases are involved. The prevalence of CVRFs, on the other hand, is high. The dermatologist should, therefore, take a more active role in detecting comorbidity and CVRFs, since psoriasis patients are usually young and no other condition has been diagnosed. In fact, these patients have often never been evaluated for other possible diseases prior to their dermatologic diagnosis.

The AQUILES study was funded by Merck Sharp & Dohme, Spain.

Cristina Sancho, Berta Juliá, and Luis Cea-Calvo are full-time employees of Merck Sharp & Dohme, Spain. The authors of this manuscript also took part in the study as investigators, and they or the institution they were affiliated with received fees for enrolling patients. The following authors declare conflicts of interest relevant to this study: Lluís Puig (presentations for Merck Sharp & Dohme), Marta Ferrán (presentations and consulting for Merck Sharp & Dohme, Pfizer, AbbVie, and Novartis), José L. Sánchez-Carazo (consultant for Merck Sharp & Dohme), Ignacio Marín-Jiménez (presentations for Merck Sharp & Dohme, AbbVie, and Shire and consultation for Merck Sharp & Dohme, Ferring, Dr. Folk Pharma, AbbVie, FAES, and Shire), and Rosario García-Vicuña (consultant for the OpenSER project for allied health professionals). The other authors declare that they have no conflicts of interest.