Researchers have known that people who are overweight or smokers have a higher risk of the chronic skin disease, which is characterized by itchy and painful plaques.

In the new study, women who said they spent more than one hour per week running or at least four hours per week doing aerobics seemed to be partially protected against psoriasis, even after their weight and other lifestyle habits were taken into account.

"What we don't know for sure at this stage is whether losing weight and exercising vigorously will prevent you from getting psoriasis," said Dr. Joel Gelfand, a dermatologist from the University of Pennsylvania Perelman School of Medicine in Philadelphia, who wasn't involved in the new study.

"But these are all things that are good to do anyway and have multiple proven benefits beyond their effect on the skin," he told Reuters Health. So it wouldn't hurt for people at risk of psoriasis, including those with a family history of the condition, to step up their exercise routine.

Data for the new report came from the long-running Nurses' Health Study II, which has been used to track risks for a range of health conditions in women.

The current analysis involved about 87,000 women without psoriasis who were surveyed on their exercise habits at three points over the course of a decade, starting when they were between 27 and 44 years old.

Over the 14 years following the first survey, just over 1,000 women were diagnosed with psoriasis.

Dr. Abrar Qureshi from Brigham and Women's Hospital in Boston and his colleagues found that women who reported the most vigorous physical activity each week were 27 percent less likely to get psoriasis than the least-active women.

About two hours of weekly running, they calculated, was tied to a 25 to 30 percent lower chance of getting psoriasis over the course of the study.

On the other hand, less-vigorous activities including walking weren't linked to a decreased risk of psoriasis, the researchers reported Monday in the Archives of Dermatology.

Qureshi said the findings only apply to women in the U.S., and further research is needed to see if there's any link between physical activity and psoriasis risk in men, for example.

The findings also don't prove that running and aerobics, themselves, directly affect the chronic skin condition.

"One of the potential concerns is, well, the women who are exercising vigorously... are they just healthy in general, and do they have other healthy lifestyle factors that are contributing to a lower risk of psoriasis?" Qureshi told Reuters Health.

Still, he said, "It's certainly plausible that in women who exercise more vigorously, there might be a lowering of inflammation in the body in general."

Body-wide inflammation is a feature of psoriasis.

Gelfand said although only severe cases of psoriasis have been tied to heart disease and diabetes, people with milder forms of the condition still often experience pain, difficulty sleeping and social isolation.

The condition has "an enormous impact on people's well-being," he said.

According to the National Institutes of Health, more than three percent of adults in the U.S. have psoriasis. It's often treated with steroid ointments or UV light exposure.

The current study was funded by both the NIH and Brigham and Women's. According to financial disclosures published with the article, Qureshi is a consultant for the pharmaceutical company Novartis, which is developing a psoriasis drug.

Qureshi said he and his colleagues are now looking at the link between exercise and psoriasis in other groups of people to see if these findings hold up.

But for now, "People who are looking for yet another reason to exercise, here's a good one," he said.

"Here's another important lifestyle change that will be beneficial on many levels."

SOURCE: bit.ly/Js53V2 Archives of Dermatology, online May 21, 2012.

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