NEW YORK: People with the chronic skin condition psoriasis may be more likely to develop type 2 diabetes as well, according to an international study involving more than half a million people.

Researchers, whose results appeared in the Archives of Dermatology, found that this was especially true in those with severe psoriasis, who were 46 per cent more likely to get a diabetes diagnosis than people without the condition, after weight and other health measures were taken into account.

Psoriasis is characterized by itchy, painful plaques on the skin. Previous studies have suggested the condition is tied to a higher chance of having heart disease, or suffering a heart attack or stroke, while other reports have hinted at a link between psoriasis and diabetes as well.

“We already knew that some of the risk factors for psoriasis and diabetes are similar, like weight,” said Rahat Azfar, at the University of Pennsylvania in Philadelphia and lead author of the study.

“We do think that psoriasis itself makes people at higher risk.”

For the study, Azfar and her colleagues consulted five years' worth of electronic medical records from about 108,000 adults in the UK with psoriasis, and about 400,000 without. None of them had diabetes at the outset.

They found that 3.7 percent of those with psoriasis were diagnosed with diabetes over the course of the study, compared with 3.4 percent of the comparison group.

When patients' age, weight and high blood pressure were accounted for, psoriasis was still tied to a higher chance of developing diabetes, especially among the 6,200 people with severe psoriasis. In that group, 6.3 percent were diagnosed with diabetes.

According to the study team, the body-wide inflammation that is seen both in people with psoriasis and type 2 diabetes may explain the link between the two conditions. Azfar said psoriasis may induce that chronic inflammation through changes in the bloodstream, thus upping the risk of diabetes.

It could also be that people with psoriasis are more depressed or exercise less, helping to explain the difference in diabetes rates, said Robert Kirsner, a dermatologist from the University of Miami Miller School of Medicine who has studied psoriasis but was not involved in the study.

So far, the data cannot prove that psoriasis directly causes diabetes. And there have not been any studies to show definitively whether the ointments, pills or injections used to treat psoriasis have any impact on a patient's chance of getting diabetes, Azfar added.

Kirsner said that patients with psoriasis should talk with their doctors about other ways to reduce their diabetes risks, such as by adopting a healthier lifestyle.

“(The study) suggests that patients with psoriasis perhaps should be followed more closely and may want to adhere to a better diet and all those things to prevent diabetes,” he said.

Two of the researchers reported financial relationships with pharmaceutical companies, including those that make diabetes and psoriasis drugs.