Comorbid autoimmune diseases and cancer risks among patients with alopecia areata: A population-based case-control study in Korea

Abstract

Background: There have been few studies on the association between alopecia areata (AA) and its comorbidities. Objectives: The aim of this study was to investigate the association between AA and comorbid conditions including autoimmune diseases and several types of cancer. Methods: This study was a retrospective case-control study based on the National Health Insurance Service–National Sample Cohort database of patients with AA and age- and sex-matched control subjects from 2003 to 2013. Results: Among 12,199 patients with AA and 60,995 control subjects, patients with AA were at significantly increased risk for Graves disease, Hashimoto thyroiditis, vitiligo, psoriasis, lupus erythematosus, and rheumatoid arthritis compared with control subjects. The risk of thyroid cancer in patients with AA was significantly increased, whereas the risk of other cancers of the breast, colon/rectum, stomach, liver, and lung was significantly decreased compared with control subjects. Limitations: The diagnosis of AA and comorbidities was identified and characterized without reviewing the detailed clinical charts. Conclusion: The risk of various autoimmune diseases and thyroid cancer was significantly increased in patients with AA. Our study also demonstrated that AA was associated with a decreased risk of breast, colon/rectum, stomach, liver, and lung cancer.