Psoriasis-hypertension: Researchers zero in on link

"Over the last several years, studies have shown that psoriasis, specifically severe psoriasis, is an independent risk factor for a variety of comorbidities, putting patients suffering with this common skin disease at an increased risk for other conditions such as heart attack and stroke," says Junko Takeshita, MD, PhD, clinical instructor in the department of Dermatology at Penn Medicine and co-first author on the study. "Knowing that psoriasis is tied to other health conditions, it's vital that we have a better understanding of the systemic effects it has on other areas of the body so that we can more closely monitor these patients and provide better and preventative care."

Defining uncontrolled hypertension as blood pressure measured as at least 140/90, the researchers found a clear relationship between psoriasis and uncontrolled hypertension in patients with a confirmed diagnosis of psoriasis. Additional finding indicate there is a significant dose-response relationship, meaning that the likelihood of uncontrolled hypertension increases with greater psoriasis severity. Results of the study reveal that the patients with the highest risk of having uncontrolled blood pressure, are those with moderate to severe psoriasis, which is defined as having at least three percent of one's body surface affected by the disease.

Takeshita and colleagues examined data from a random sample of psoriasis patients included in The Health Improvement Network (THIN), an electronic medical database based in the United Kingdom that collects demographic, diagnostic, treatment, and laboratory information from a broad representative sample of the UK population. Takeshita says the psoriasis diagnostic code in the database has been validated through extensive studies looking at the condition.

The researchers concentrated on a specific group within the THIN database called the Incident Health Outcomes and Psoriasis Events (iHOPE) cohort, a random sample of about 9000 patients with a confirmed diagnosis of psoriasis and disease severity classified by their general practitioners using objective measures, specifically body surface area involvement. This permitted a level of analysis not possible in previous studies.

"Most large electronic databases such as THIN do not have information such as body surface area involvement or other direct measures of psoriasis severity, and we usually have to use surrogate measures such as receipt of a treatment that is indicated for more severe psoriasis to define psoriasis severity," Takeshita explains. "The use of surrogate measures to define psoriasis severity is not ideal for multiple reasons. For example, we know that many patients with psoriasis go untreated, so using treatment to define psoriasis severity may incorrectly identify patients who truly have severe disease as having mild disease. Furthermore, when we use treatments to define psoriasis severity, we cannot separate effects of psoriasis itself from potential psoriasis treatment effects on blood pressure control. To our knowledge, ours is the first study to evaluate the effect of objectively determined psoriasis severity on blood pressure control."

Although the work strongly suggests a correlation between hypertension and psoriasis, the cross-sectional nature of the study doesn't allow one important issue to be addressed: the "chicken or egg" question of whether psoriasis may cause hypertension or whether the presence of hypertension contributes to psoriasis. Still, the present study provides an ideal starting point for that next investigative step.

"Determining the cause and effect is something that needs to be evaluated in future longitudinal studies so that we can better assess which condition developed first," Takeshita explains. "Our hypothesis is that the psoriasis and the inflammation that comes with it are making the hypertension worse, but certainly it could go the other way, and understanding which comes first has important implications for how we care for these patients and our understanding of how these two conditions are related."