title: Seasonal change in the exacerbations of Crohn's disease.
abstract: BACKGROUND
  Ulcerative colitis (UC) has been reported to run a clinical course with seasonal exacerbations in both retrospective and prospective studies; such a seasonality was not been observed, however, in Crohn's disease (CD).
  
  
  METHODS
  The monthly distribution in the relapse of CD was retrospectively studied to ascertain whether there is any seasonal variation in the exacerbations of the disease. During the period of 1972 to 1993, 139 patients who had been regularly followed up for at least 13 consecutive months were analyzed.
  
  
  RESULTS
  In a total of 10,693 follow-up months for these patients 592 relapses occurred in the study period. The highest relapse rate was found in the autumn and winter, whereas the lowest was in the summer.
  
  
  CONCLUSIONS
  This study shows that CD runs a clinical course with seasonal exacerbations, suggesting that seasonal or exogenous factors may be involved in the relapse of CD.
authors.affiliation: Dept. of Medicine, Vancouver Hospital, B.C., Canada.
authors.forename: L
authors.initials: L
authors.lastname: Zeng
authors.forename: F H
authors.initials: FH
authors.lastname: Anderson
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001955:British Columbia; D003424:Crohn Disease / Q000209:etiology / Q000473:pathology / Q000503:physiopathology*; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D012008:Recurrence; D012189:Retrospective Studies; D012307:Risk Factors; D012621:Seasons