title: Seasonal variations in the onset of ulcerative colitis in Japan.
abstract: OBJECTIVE
  To investigate seasonal variations in the onset and relapse of ulcerative colitis (UC) in Japanese patients.
  
  
  METHODS
  Between 1994 and 2006, 198 Japanese patients diagnosed with UC according to conventional criteria in an academic hospital were enrolled for onset evaluation. Among 265 Japanese patients with UC who were observed for more than 12 mo, 165 patients relapsed (239 times) and were enrolled for relapse evaluation. The patients' symptoms were recorded each month for 12 consecutive years.
  
  
  RESULTS
  There was monthly seasonality in symptom onset during October and March for UC. The onset of symptoms in UC patients frequently occurred during the winter. Variation in UC onset was observed according to both month (P = 0.015) and season (P = 0.048). Relapse commonly occurred in October, and variations in relapse were not significant either in month (P = 0.52) or season (P = 0.12). Upper respiratory inflammation was the main factor responsible for relapse.
  
  
  CONCLUSIONS
  Our results suggest that environmental factors associated with winter and spring seasonality may be responsible for triggering the clinical onset of UC in Japan.
authors.affiliation: Shigeo Koido, Toshifumi Ohkusa, Kan Uchiyama, Hiroshi Arakawa, Hisao Tajiri, Division of Gastroenterology and Hepatology, Department of Internal Medicine, the Jikei University School of Medicine, Chiba 277-8567, Japan.
authors.forename: Shigeo
authors.initials: S
authors.lastname: Koido
authors.affiliation: Shigeo Koido, Toshifumi Ohkusa, Kan Uchiyama, Hiroshi Arakawa, Hisao Tajiri, Division of Gastroenterology and Hepatology, Department of Internal Medicine, the Jikei University School of Medicine, Chiba 277-8567, Japan.
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Ohkusa
authors.affiliation: Shigeo Koido, Toshifumi Ohkusa, Kan Uchiyama, Hiroshi Arakawa, Hisao Tajiri, Division of Gastroenterology and Hepatology, Department of Internal Medicine, the Jikei University School of Medicine, Chiba 277-8567, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Saito
authors.affiliation: Shigeo Koido, Toshifumi Ohkusa, Kan Uchiyama, Hiroshi Arakawa, Hisao Tajiri, Division of Gastroenterology and Hepatology, Department of Internal Medicine, the Jikei University School of Medicine, Chiba 277-8567, Japan.
authors.forename: Tetsuji
authors.initials: T
authors.lastname: Yokoyama
authors.affiliation: Shigeo Koido, Toshifumi Ohkusa, Kan Uchiyama, Hiroshi Arakawa, Hisao Tajiri, Division of Gastroenterology and Hepatology, Department of Internal Medicine, the Jikei University School of Medicine, Chiba 277-8567, Japan.
authors.forename: Tomoyoshi
authors.initials: T
authors.lastname: Shibuya
authors.affiliation: Shigeo Koido, Toshifumi Ohkusa, Kan Uchiyama, Hiroshi Arakawa, Hisao Tajiri, Division of Gastroenterology and Hepatology, Department of Internal Medicine, the Jikei University School of Medicine, Chiba 277-8567, Japan.
authors.forename: Naoto
authors.initials: N
authors.lastname: Sakamoto
authors.affiliation: Shigeo Koido, Toshifumi Ohkusa, Kan Uchiyama, Hiroshi Arakawa, Hisao Tajiri, Division of Gastroenterology and Hepatology, Department of Internal Medicine, the Jikei University School of Medicine, Chiba 277-8567, Japan.
authors.forename: Kan
authors.initials: K
authors.lastname: Uchiyama
authors.affiliation: Shigeo Koido, Toshifumi Ohkusa, Kan Uchiyama, Hiroshi Arakawa, Hisao Tajiri, Division of Gastroenterology and Hepatology, Department of Internal Medicine, the Jikei University School of Medicine, Chiba 277-8567, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Arakawa
authors.affiliation: Shigeo Koido, Toshifumi Ohkusa, Kan Uchiyama, Hiroshi Arakawa, Hisao Tajiri, Division of Gastroenterology and Hepatology, Department of Internal Medicine, the Jikei University School of Medicine, Chiba 277-8567, Japan.
authors.forename: Taro
authors.initials: T
authors.lastname: Osada
authors.affiliation: Shigeo Koido, Toshifumi Ohkusa, Kan Uchiyama, Hiroshi Arakawa, Hisao Tajiri, Division of Gastroenterology and Hepatology, Department of Internal Medicine, the Jikei University School of Medicine, Chiba 277-8567, Japan.
authors.forename: Akihito
authors.initials: A
authors.lastname: Nagahara
authors.affiliation: Shigeo Koido, Toshifumi Ohkusa, Kan Uchiyama, Hiroshi Arakawa, Hisao Tajiri, Division of Gastroenterology and Hepatology, Department of Internal Medicine, the Jikei University School of Medicine, Chiba 277-8567, Japan.
authors.forename: Sumio
authors.initials: S
authors.lastname: Watanabe
authors.affiliation: Shigeo Koido, Toshifumi Ohkusa, Kan Uchiyama, Hiroshi Arakawa, Hisao Tajiri, Division of Gastroenterology and Hepatology, Department of Internal Medicine, the Jikei University School of Medicine, Chiba 277-8567, Japan.
authors.forename: Hisao
authors.initials: H
authors.lastname: Tajiri
mesh_terms: D000046:Academic Medical Centers; D000328:Adult; D003093:Colitis, Ulcerative / Q000175:diagnosis / Q000453:epidemiology*; D004777:Environment; D005260:Female; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D012008:Recurrence; D012307:Risk Factors; D012621:Seasons; D013997:Time Factors; D055815:Young Adult
keywords: Japanese population; Onset; Relapse; Seasonal variations; Ulcerative colitis