Other Possible Explanations
Exposure to ultraviolet light is a psoriasis treatment, so time spent outdoors exercising, and not the exercise itself, might have explained the lowered risk of the disease, Qureshi says. But his study found that women who ran for only an hour a week had a significantly reduced risk of developing psoriasis than women who spent at least four hours walking outside at an average pace.
Chris Ritchlin, MD, MPH, a University of Rochester rheumatologist, calls Qureshi's findings "very interesting." Still, Ritchlin says, while exercise is known to be associated with reduced inflammation, "is there something about people who are really athletically inclined that we're not thinking about that would prevent them from getting psoriasis?"
Qureshi says that could be the case, which is why his study needs to be replicated. "You have to interpret the results cautiously because it is a single study," he says. "It is certainly possible that the women who exercise more are just more health-conscious. There could be other factors that could protect them from developing psoriasis."
Qureshi's study appears online in the Archives of Dermatology.