The findings are reported in the article, "Psoriasis and Hypertension Severity: Results from a Case-Control Study," which is now available online in PLoS ONE, the open-access journal for the communication of peer-reviewed scientific and medical research.
"Our study makes a strong case that psoriasis is not just a skin-deep disease," said April W. Armstrong, assistant clinical professor of dermatology and principal investigator and lead author of the study. "We are beginning to find that psoriasis may represent a window into detecting cardiovascular conditions, including hypertension."
Psoriasis affects about 4 percent of the U.S. population and causes patches of itchy, thickened, dry, reddened skin. It is passed down in families and is believed to be caused by a person's immune system mistakenly attacking one's own skin cells. The severity of the condition varies considerably among individuals and over time. It often flares up during dry weather or with infections.
"The study's findings can alert primary-care providers, cardiologists and nephrologists, all of whom frequently treat hypertension," said Armstrong. "Hypertensive patients who also have psoriasis are likely to need closer monitoring and a more aggressive drug regimen to achieve adequate blood-pressure control."
The UC Davis study involved 835 patients who had both psoriasis and hypertension. Their cases were compared with more than 2,400 other individuals (the control group) who had hypertension but not psoriasis. Hypertension severity was based on the levels of treatment, ranging from lifestyle modifications to medications and central-acting agents that target the central nervous system.
The highest level of treatment, which relies on a central-acting agent (also known as adrenergic inhibitors), is reserved for those individuals whose blood pressure cannot be controlled by conventional medications. Patients with psoriasis were found to need significantly more of these types of intensive blood pressure therapies than those without psoriasis. For example, hypertensive patients with psoriasis were nearly 20 times more likely to be on four drugs, or on a central-acting agent, than were hypertensive patients without psoriasis. The findings were found to be significant even after statistically controlling for other risk factors associated with hypertension, including diabetes, smoking and high cholesterol.
Hypertension is a key risk factor for cardiovascular disease and increases a person's chance of having a heart attack or stroke. The link between psoriasis and cardiovascular disease was first reported in the medical literature in the 1970s, and since then researchers have developed a number of inconclusive theories to explain the connection:
According to Armstrong, it is unlikely that drugs used to treat psoriasis are responsible for the increased severity of hypertension. Most drugs used to treat the condition are applied only to the skin and not absorbed enough into the bloodstream to have widespread effects. Oral medications for psoriasis that might affect blood pressure are generally used only for brief periods during severe flare-ups of the condition.
Armstrong, who directs her department's clinical research unit, is now leading a group of investigators in studying whether people with psoriasis also have more severe coronary artery disease.
"Our understanding of psoriasis as a systemic disease is rapidly evolving," said Armstrong. "A better appreciation of the other conditions that tend to accompany psoriasis could potentially drive our therapy of the disease in the future."