The Association Between Physical Activity and the Risk of Incident Psoriasis

Objective: To examine the association between total physical activity, walking, and vigorous exercise and the incidence of psoriasis in women. Design: Cohort study. Setting: The Nurses' Health Study II, a cohort of 116 430 women aged 27 to 44 years in 1991. Participants: The study population included 86 655 US female nurses who reported whether they had ever been diagnosed as having psoriasis and who completed detailed physical activity questionnaires in 1991, 1997, and 2001. We excluded participants with a history of psoriasis prior to 1991. Main Outcome Measures: Risk of psoriasis by quintile of physical activity as measured by a metabolic equivalent task score. Results: We documented 1026 incident psoriasis cases during 1 195 703 person-years of follow-up (14 years, 1991-2005). After adjusting for age, smoking, and alcohol use, increasing physical activity was inversely associated with the risk of psoriasis. The most physically active quintile of women had a lower multivariate relative risk (RR) of psoriasis (0.72 [95% CI, 0.59-0.89; P<.001 for trend]) compared with the least active quintile. Vigorous physical activity (>= 6 metabolic equivalents) was associated with a reduced risk of psoriasis (multivariate RR for the highest quintile, 0.66 [95% CI, 0.54-0.81; P<.001 for trend]); this association remained significant after adjusting for body mass index (RR, 0.73 [95% CI, 0.60-0.90; P=.009 for trend]). Walking was not associated with psoriasis risk. In a subset of 550 confirmed psoriasis cases, we observed a similarly reduced risk of psoriasis associated with vigorous physical activity (multivariate RR for the highest quintile, 0.64 [95% CI, 0.48-0.86; P=.03 for trend]). Conclusion: In this study of US women, vigorous physical activity is independently associated with a reduced risk of incident psoriasis.