(HealthDay) -- Coffee and caffeine are not associated with psoriasis incidence after adjustment for smoking, according to a research letter published in the March issue of the Archives of Dermatology.
Wenqing Li, Ph.D., from the Brigham and Women's Hospital and Harvard Medical School in Boston, and colleagues investigated the long-term association between coffee and caffeine intake and psoriasis in 82,539 U.S. women, free from psoriasis in 1991, using data from the Nurses' Health Study II. Participants completed questionnaires in 2005 to identify the incidence of psoriasis and were asked about food and beverage intake in 1991, 1995, 1999, and 2003.
During 1,140,758 person-years of follow-up, the researchers identified 986 incident cases of psoriasis. In an age-adjusted model, the risk of psoriasis was moderately increased with increasing coffee consumption. The association was no longer significant after adjustment for smoking. The association between decaffeinated coffee and the risk of psoriasis was not significant. There was a trend toward increased risk of psoriasis with increased caffeine intake in an age-adjusted model; however, the association was no longer significant following adjustment for smoking.
"We did not observe a material change of psoriasis incidence associated with coffee or caffeine intake, after adjusting for known confounders," the authors write. "Smoking appears to be the major confounder underlying the observed significant association between coffee and caffeine intake and risk of psoriasis in age-adjusted models."
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