A study of U.S. women suggests that vigorous physical activity may be associated with a reduced risk of psoriasis, according to a report published Online First by Archives of Dermatology, a JAMA Network publication.

Psoriasis is an immunologic disorder characterized by systemic inflammation and scaling of the skin. Physical activity has been associated with a decreased risk of disorders characterized by systemic inflammation, including type 2 diabetes, colon cancer, coronary artery disease and breast cancer, according to the study background.

"Our results suggest that participation in at least 20.9 MET (metabolic equivalent task)-hours per week of vigorous exercise, the equivalent of 105 minutes of running or 180 minutes of swimming or playing tennis, is associated with a 25 percent to 30 percent reduced risk of psoriasis compared with not participating in any vigorous exercise," the authors note.

Hillary C. Frankel, A.B., of Brigham and Women's Hospital, Boston, and colleagues used data from the Nurses' Health Study II. Their analysis included 86,665 women who did not have psoriasis at baseline in 1991 and who completed physical activity questionnaires in 1991, 1997 and 2001. Researchers documented 1,026 incident cases of psoriasis as they examined the association between physical activity and the disorder.

The most physically active women had a lower multivariate relative risk of psoriasis (0.72) compared with the least active. Walking was not associated with a reduced risk of psoriasis, according to study results.

"Among the individual vigorous activities we evaluated, only running and performing aerobic exercise or calisthenics were associated with a reduced risk of psoriasis. Other vigorous activities, including jogging, playing tennis, swimming and bicycling were not associated with psoriasis risk," the authors note. "The highly variable intensity at which these activities are performed may account for this finding."

The authors suggest that how physical activity may reduce psoriasis risk deserves further study.

"In addition to providing other health benefits, participation in vigorous exercise may represent a new preventive measure for women at high risk of developing psoriasis. Additional corroborative studies and further investigations into the mechanisms by which physical activity protects against new-onset psoriasis are needed," the researchers conclude.