Physical Activity May Reduce Psoriasis Risk

Joe Barber Jr, PhD

May 21, 2012

May 21, 2012 — Vigorous physical activity appeared to reduce the risk for psoriasis among a group of female nurses in the United States, according to the findings of a cohort study.

Hillary C. Frankel, from Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, and colleagues published their findings online May 21 issue of the Archives of Dermatology.

The researchers noted that there was some evidence that physical activity has beneficial effects on inflammatory disorders. "Physical activity has been associated with a decreased risk of disorders characterized by systemic inflammation, including type 2 diabetes mellitus, colon cancer, coronary artery disease, and breast cancer," the authors write. "It is biologically plausible that physical activity may affect psoriasis risk through effects on systemic inflammatory mediators."

The authors used the data for 86,665 US female nurses who enrolled in the Nurses' Health Study II, a longitudinal study of 116,430 female registered nurses from 15 states who were 25 to 42 years of age in 1989 and who completed detailed physical activity questionnaires in 1991, 1997, and 2001. The most active women (≥31.9 metabolic equivalent task (MET)-hours/week) had a much lower age-adjusted risk for psoriasis than the least active women (risk ratio [RR], 0.71; 95% confidence interval [CI], 0.58 - 0.87; P < .001 for trend), and the risk remained significantly different after adjustment for age, smoking, and alcohol intake (RR, 0.72; 95% CI, 0.59 - 0.89; P < .001 for trend).

The authors excluded women who had a psoriasis diagnosis before 1991 and women with no reported date of diagnosis. The authors adjusted for age, smoking status, alcohol intake, and body mass index (BMI) in the multivariate analysis.

Vigorous activity (≥20.9 MET-hours/week) was associated with a lower risk for psoriasis compared with no activity (RR, 0.66; 95% CI, 0.54 - 0.80; P < .001 for trend), and this effect remained significant after adjustment for age, smoking status, and alcohol intake (RR, 0.66; 95% CI, 0.54 - 0.81; P < .001 for trend) and with adjustment for BMI as well (RR, 0.73; 95% CI, 0.60 - 0.90; P = .009 for trend). However, no association was observed between walking and reduced psoriasis risk (RR, 0.85; 95% CI, 0.60 - 1.20; P = .45 for trend.

For the women in the study with self-reported psoriasis, a subset of 550 women with confirmed psoriasis per the Psoriasis Screening Tool questionnaire were evaluated. With adjustments for age, smoking, and alcohol intake, the women in this subset with the highest quintiles of total physical activity (RR, 0.62; 95% CI, 0.46 - 0.84; P = .001 for trend) and vigorous activity (RR, 0.57; 95% CI, 0.43 - 0.76; P = .002 for trend) had lower risks for psoriasis than women in the lowest corresponding quintiles. When adjustment for BMI was added, this significant trend remained for vigorous activity (RR, 0.64; 95% CI, 0.48 - 0.86; P = .03) but not for total amount of physical activity (RR, 0.75; 95% CI, 0.56 - 1.02; P = .08).

The limitations of the study included its reliance on self-reported psoriasis diagnosis rather than diagnosis by dermatologists; its lack of randomization; and the inability to control for such confounders as socioeconomic factors, healthcare access, and stress. In addition, there was no distinction made between indoor and outdoor physical activity, which may be relevant given the potential influence of ultraviolet exposure on psoriasis.

Health Behaviors May Trump Genes When It Comes to Psoriasis

The authors concluded that their findings of "a dose response gradient" "supports a causal association" between physical activity and reduced psoriasis risk. "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," the authors write. "Additional corroborative studies and further investigations into the mechanisms by which physical activity protects against new-onset psoriasis are needed."

April W. Armstrong, MD, MPH, from the University of California Davis Health System in Sacramento, concurred with the authors' assessments. "We know that genetics plays a significant role in the development of psoriasis," Dr. Armstrong told Medscape Medical News by email. "What we didn't know until now is the role that health behaviors such as vigorous exercise may play in modifying psoriasis risks. This article contributes to our understanding in that regard."

This work was supported by a grant from the National Institutes of Health and by the Department of Dermatology, Brigham and Women's Hospital. One coauthor serves as a consultant to Norvartis and the Centers for Disease Control and Prevention. The other authors and Dr. Armstrong have disclosed no relevant financial relationships.

Arch Dermatol. Published online May 21, 2012.

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