title: Comorbidity profiles among patients with alopecia areata: the importance of onset age, a nationwide population-based study.
abstract: BACKGROUND
  Alopecia areata (AA) is considered an autoimmune disease with undetermined pathogenesis. Age at onset predicts distinct outcomes. A nationwide study of the relationship of AA with associated diseases stratified by onset age has rarely been reported.
  
  
  OBJECTIVE
  We sought to clarify the role of atopic and autoimmune diseases in AA, thereby better understanding its pathogenesis.
  
  
  METHODS
  A total of 4334 patients with AA were identified from the National Health Insurance Database in Taiwan from 1996 to 2008. A national representative cohort of 784,158 persons served as control subjects.
  
  
  RESULTS
  Among patients with AA, there were significant associations with vitiligo, lupus erythematosus, psoriasis, atopic dermatitis, autoimmune thyroid disease, and allergic rhinitis. Different ages at onset resulted in disparate comorbidities. Increased risk of atopic dermatitis (odds ratio [OR] 3.82, 95% confidence interval 2.67-5.45) and lupus erythematosus (OR 9.76, 95% confidence interval 3.05-31.21) were found in childhood AA younger than 10 years. Additional diseases including psoriasis (OR 2.43) and rheumatoid arthritis (OR 2.57) appeared at onset age 11 to 20 years. Most atopic and autoimmune diseases were observed at onset ages of 21 to 60 years. With onset age older than 60 years, thyroid disease (OR 2.52) was highly related to AA. Moreover, patients with AA had higher risk for more coexisting diseases than control subjects.
  
  
  CONCLUSIONS
  We could not differentiate hypothyroidism from hyperthyroidism.
  
  
  CONCLUSIONS
  AA is related to various atopic and autoimmune diseases. Different associated diseases in each onset age group of AA can allow clinician to efficiently investigate specific comorbidities.
authors: Department of Dermatology, Taipei Veterans General Hospital, Taipei, Taiwan.
authors: Szu-Ying
authors: SY
authors: Chu
authors: Yi-Ju
authors: YJ
authors: Chen
authors: Wei-Cheng
authors: WC
authors: Tseng
authors: Ming-Wei
authors: MW
authors: Lin
authors: Tzeng-Ji
authors: TJ
authors: Chen
authors: Chian-Yaw
authors: CY
authors: Hwang
authors: Chih-Chiang
authors: CC
authors: Chen
authors: Ding-Dar
authors: DD
authors: Lee
authors: Yun-Ting
authors: YT
authors: Chang
authors: Wen-Jen
authors: WJ
authors: Wang
authors: Han-Nan
authors: HN
authors: Liu