The amount and duration of smoking is correlated with the risk of psoriasis, according to research published in the Journal of the American Academy of Dermatology.

Eun Joo Lee, PhD, from the National Health Insurance Service, Wonjusi, Republic of North Korea, and colleagues conducted a nationwide cohort study using data from the Korean National Health Insurance database from 2005 through 2015. The researchers included 17,055,608 participants older than 20 years of age who underwent a health examination between 2005 and 2008 and who were followed for 8 years.

Compared with nonsmokers, former smokers (adjusted incidence ratio [IR], 1.11) and current smokers (IR, 1.14) had a significantly higher risk for developing psoriasis. The results suggest that smoking status is a potential independent risk factor for psoriasis.

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The investigators also found that the risk of psoriasis was increased with the amount and duration of smoking, and there was a statistically significant positive correlation between risk of psoriasis and the total period of smoking. The hazard ratios (HR) for psoriasis were 1.11 among individuals who smoked fewer than 0.5 packs per day and 1.25 among individuals who smoked more than 2 packs per day.

“We clearly showed that there is a positive correlation between the amount and/or duration of smoking and the occurrence of psoriasis,” the investigators wrote. “However, our study has a limitation in that any change in smoking status after registration has not been reflected. In addition, association does not demonstrate cause and effect; therefore, further investigation is needed.”

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Lee EJ, Han KD, Han JH, Lee JH. Smoking and risk of psoriasis: A nationwide cohort study. J Am Acad Dermatol. 2017;77(3):573-575. doi:10.1016/j.jaad.2017.04.015