Increased Risk of Chronic Spontaneous Urticaria in Patients With Autoimmune Thyroid Diseases: A Nationwide, Population-based Study.

There was no previous population-based study on the comparison of the risk of chronic spontaneous urticaria (CSU) between autoimmune thyroid diseases (AITD) and age- and gender-matched controls. The primary objective of this study was to evaluate the risk of CSU after diagnosis of AITD using national registry data from Korea. The secondary objective was to evaluate other risk factors of CSU. Based on the disease code diagnoses in 2003-2005, we composed an AITD group (n=3,659) and an age- and gender-matched control group (n=18,295). Each patient was tracked for whether CSU occurs or not until 2013. After adjusting for demographic differences and comorbidities, patients with AITD had a significantly higher rate of CSU compared to the control group (hazard ratio [HR], 1.46; 95% confidence interval [CI], 1.25-1.70; P<0.001). Among the AITD patients, the adjusted HR for CSU was higher in patients with Hashimoto's thyroiditis (HR, 1.50) than in those with Grave's disease (HR, 1.33), although the difference was not statistically significant (P=0.368). Analysis of CSU patients associated with AITD showed that female patients had a significantly higher risk of CSU compared to male ones (HR, 1.34; P=0.001) and that those with allergic rhinitis (HR, 1.51; P<0.001), atopic dermatitis (HR, 2.44; P<0.001), and asthma (HR, 1.50; P<0.001) had a significantly higher risk of CSU compared to patients without respective diseases. Our results demonstrated that AITD could be significantly associated with an increased risk of CSU.