Epidemiology and comorbidities of patients with chronic urticaria in Taiwan: A nationwide population-based study Chia-Yu Chu a , Yung-Tsu Cho a , Jhih-Hua Jiang b , Eve I-Chun Lin c , Chao-Hsiun Tang b, * a Department of Dermatology, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan b School of Health Care Administration, Taipei Medical University, Taipei, Taiwan c Novartis (Taiwan) Co., Ltd., Taipei, Taiwan A R T I C L E I N F O Article history: Received 12 May 2017 Received in revised form 21 June 2017 Accepted 11 July 2017 Keywords: Comorbidity Psychiatric disorders Rheumatic diseases Thyroid disorders Urticaria A B S T R A C T Background: Comprehensive data regarding the epidemiology of chronic urticaria (CU) in general populations are scant. Objectives: To investigate the prevalence, incidence, and comorbidities of CU in general population. Methods: The data were sourced from the National Health Insurance Research Database (NHIRD) for 2009–2012. Patients who had a primary/secondary ICD-9-CM diagnosis code of 708.1, 708.8, or 708.9 during the year with at least two outpatient visits and an antihistamine prescription, were identified as the cases of CU for each year. The incidence, persistence and comorbidities of CU were examined. Results: The prevalence of CU ranged from 0.69% to 0.79% for each year from 2009 to 2012, and the incidence was around 0.50% per year from 2010 to 2012. Comparing to the Standard Population, the standardized prevalence ratios (SPRs) for the rheumatic diseases, thyroid disorders, inflammatory diseases, and psychiatric disorders among CU patients were 2.74, 1.81, 1.57 and 1.87, respectively. Conclusion: The prevalence of CU in Taiwan is about 0.69-0.79%. CU is associated with a significantly increased risk of psychiatric disorders, inflammatory diseases, thyroid disorders, and rheumatic diseases. Except for thyroid disorders, the prevalence of these comorbidities tends to increase the longer CU persists. © 2017 Published by Elsevier Ireland Ltd on behalf of Japanese Society for Investigative Dermatology. 1. Introduction Chronic urticaria (CU) is defined by the repeated occurrence of itchy hives, angioedema, or both, for 6 weeks or more. It is further classified into chronic inducible urticaria and chronic spontaneous (or idiopathic) urticaria (CSU/CIU), depending on whether a specific trigger can be identified or not [1–3]. Although urticaria is one of the most common skin conditions, only a few studies investigating the prevalence of CU have been published [4]. Most data have involved selected patient populations, usually patients attending special clinics [4,5]. In addition, previous inconsistencies in the classification of CU present further difficulties when comparing past studies [4]. A 1-year period prevalence for CU of 0.8% was reported in a German study [5], while Gaig et al. reported a point prevalence of 0.6% in the Spanish population [6]. However, the prevalence and incidence of CU in Asian populations are largely unknown. It has been suggested that CU might be related to other autoimmune processes, rheumatic diseases, or chronic inflamma- tion [7–9]. The association of CU with rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), ankylosing spondylitis (AS), psoriatic arthritis/psoriasis (PsA/PsO), thyroid disorders, inflam- matory diseases, and psychiatric disorders has been reported before [7–17]. However, there is limited information on how prevalent they are. In this study, we aimed to investigate the prevalence, incidence, and comorbidities of CU in the general population of Taiwan. 2. Methods 2.1. Setting The National Health Insurance (NHI) program in Taiwan was put into effect in March of 1995, and is primarily funded by payroll tax Abbreviations: AS, ankylosing spondylitis; CIU, chronic idiopathic urticaria; CSU, chronic spontaneous urticaria; CU, chronic urticaria; H. pylori, Helicobacter pylori; ICD-9-CM, International Classification of Diseases, Ninth Revision, Clinical Modification; NHI, National Health Insurance; NHIRD, National Health Insurance Research Database; PsA/PsO, psoriatic arthritis/psoriasis; RA, rheumatoid arthritis; SLE, systemic lupus erythematosus; SPR, standardized prevalence ratio. * Corresponding author at: School of Health Care Administration, Taipei Medical University, 250 WuXin Street, Taipei City, 110, Taiwan. E-mail address: chtang@tmu.edu.tw (C.-H. Tang). http://dx.doi.org/10.1016/j.jdermsci.2017.07.006 0923-1811/ © 2017 Published by Elsevier Ireland Ltd on behalf of Japanese Society for Investigative Dermatology. Journal of Dermatological Science 88 (2017) 192–198 Contents lists available at ScienceDirect Journal of Dermatological Science journal homepa ge: www.jdsjournal.com