MONDAY, April 20, 2009 (Health.com) — Psoriasis may do more than wreak havoc on your skin. Those scaly, red patches are also associated with a higher risk of diabetes and high blood pressure, possibly due to the underlying inflammation that causes the skin problem.
Women with psoriasis are 63% more likely to develop diabetes, and 17% more likely to develop high blood pressure than their counterparts who do not have the common skin condition, according to a study in the April issue of the Archives of Dermatology.
"Psoriasis is not just a skin disease. It is a real medical condition and requires a multidisciplinary approach to treatment," says lead researcher Abrar A. Qureshi, MD, MPH, an assistant professor of dermatology at Brigham and Women's Hospital and Harvard University Medical School, both in Boston.
Psoriasis affects more than 4.5 million adults in the United States, according to the American Academy of Dermatology. The skin condition can be mild to severe, and is marked by scaly, silvery plaques of raised, reddish skin that tend to occur on the elbows, knees, lower back, and scalp.
In the study, the researchers analyzed data from the Nurses' Health Study II, which included 78,061 nurses who were ages 27 to 44 in 1991. Overall, 2.3% had been diagnosed with psoriasis. The women were asked whether they were diagnosed with diabetes or high blood pressure during a 14-year follow-up period.
Of all the women in the study, 2% developed diabetes and 20% developed high blood pressure. The women with psoriasis were more likely to develop diabetes and/or high blood pressure than the women who did not have psoriasis when the study began.
Next page: Inflammation may link all three conditions
There was still a link even after researchers took into account obesity and smoking, other factors that increase the chance diabetes and high blood pressure. "Women with psoriasis are at risk for developing diabetes, even if they are not overweight," Dr. Qureshi explains.
It's not clear how the conditions are linked and whether aggressively treating the skin disease will reduce—or possibly increase—the risk of developing other diseases.
Dr. Qureshi says the likely link between psoriasis, high blood pressure and diabetes is inflammation. "Clearly both diabetes and high blood pressure are considered to be inflammatory in nature and psoriasis is also inflammatory, so widespread inflammation in the body may be the common thread," he says. Put another way: "If you have one inflammatory condition like psoriasis, you may be at risk for another."
Inflammation is a promising theory, but it's not the only one. Some people with psoriasis are more likely than those without the skin condition to engage in unhealthy behaviors such as smoking, or may not get as much exercise as those without the condition. Smoking and a sedentary lifestyle can increase the risk of high blood pressure and diabetes.
Another possibility is that high doses of corticosteroids used to treat psoriasis may raise diabetes risk. Oral steroids are known to increase blood sugar levels, but psoriasis is not routinely treated with oral steroids in the United States. Topical steroids, on the other hand, are commonly used to treat psoriasis. If they are used on large areas of the skin, the body could theoretically absorb the drugs.
However, most people have trouble complying with regimens that require long-term use of topical steroids—so this is unlikely to be the cause, says Dr. Qureshi.
The study authors did not gather information on how the women were treated for psoriasis.
The researchers are now measuring blood levels of inflammatory markers and hormones to see if the same factors that are known to be elevated in people with diabetes or high blood pressure are also elevated in people with psoriasis. The findings could have important ramifications for how psoriasis is treated.
"It would be hard to predict whether treating psoriasis would reduce the risk of diabetes or hypertension, but it would make sense if we prove that inflammation is the cause," Dr. Qureshi says. "We just don't know that for sure yet," he says.
Next page: How to reduce your risk
In the meantime, people with psoriasis should take heart; there are many ways to reduce the risk of cardiovascular problems often associated with diabetes and high blood pressure, Dr. Qureshi adds. "If you have psoriasis, you should start thinking about risk factors that impact your heart. If you are overweight, lose weight, go for nutritional counseling and/or increase your physical activity and if you smoke, go for smoking cessation counseling."
In an accompanying editorial, William H. Eaglestein, MD, of Stiefel Laboratories in Palo Alto, Calif. and Jeffrey P. Callen, MD, of the University of Louisville in Kentucky, point out that this is not the first time that psoriasis and diabetes have been linked—but it is the first prospective study. Prospective studies are considered to be a good way to establish health risks because they follow a group of people over time.
Neil Sadick, MD, a New York City–based dermatologist and clinical professor of dermatology at Weill Cornell Medical College, says that psoriasis should raise red flags suggesting a patient could be at risk for other diseases such as diabetes.
"If you have psoriasis, we need to be sure that you don't have any risk factors for heart disease such as diabetes or high blood pressure," he says. "If you are diagnosed with psoriasis, get a good general examination from your internist and make sure to tell him or her if you have a family history of any of these conditions."
Although there is no proof that aggressively treating psoriasis will mitigate any of these risks, "I would want to really keep the psoriasis under good control and treat or prevent any heart disease risk factors that occur."