The risk of psoriasis in patients with allergic diseases: A nationwide population-based cohort study

The spectrum of allergic diseases includes atopic dermatitis (AD), allergic rhinitis (AR), and asthma. To date, the association between allergic diseases and psoriasis has not yet been completely evaluated. This study was conducted to determine the risk of psoriasis in patients with allergic diseases. A health screening database, a sub-dataset of the Korean National Health Insurance Service database, was used. All 9,718,722 subjects who underwent health examination in 2009 at age over 20 were included. Subjects with allergic diseases including AD (n = 35,685), AR (n = 1,362,713), asthma (n = 279,451) and control subjects without all three allergic diseases (n = 8,210,042), without AD (n = 9,683,037), without AR (n = 8,356,009) and without asthma group (n = 9,439,271) were analyzed. The subjects were tracked using their medical records during the 8-year period from 2010 to 2017 to identify those who developed psoriasis. Multivariate Cox regression models were used to assess the risk of psoriasis. The incidence probability of psoriasis was analyzed through the Kaplan-Meier method. The incidence of psoriasis per 1,000 person-years was 9.57, 3.78, and 4.28 in the AD, AR, and asthma groups, respectively. The AD group exhibited a significantly increased risk of developing psoriasis compared to subjects without AD (hazard ratio [HR], 3.18; 95% confidence interval [95% CI], 3.05-3.31; P < 0.001) after adjustment for confounding factors. The risk of psoriasis was significantly increased in the AR group compared to subjects without AR (HR, 1.32; 95% CI, 1.31-1.34; P < 0.001) and asthma group compared to subjects without asthma (HR, 1.30; 95% CI, 1.27-1.33; P < 0.001). Allergic diseases, particularly AD, may be a risk factor for psoriasis.