title: Seasonal variation in exacerbations of ulcerative colitis.
abstract: OBJECTIVE
  The aim of this study was to determine whether there is seasonal variability in exacerbations of ulcerative colitis.
  
  
  METHODS
  The timing of ulcerative colitis relapses was retrospectively studied in a group of consecutive patients with quiescent ulcerative colitis. Ninety-four patients were followed-up at least every three months for a mean of 29.3 (range: 12-67) months.
  
  
  RESULTS
  In total, 248 relapses of ulcerative colitis were observed with a mean number of 2.6 (range: 0-9) per patient. The timing of the relapses was characterized by a clear monthly and seasonal pattern (p < 0.001). In particular, the occurrence of relapses peaked during October and November (observed/expected (O/E): 30/20 in both months) and showed three troughs: during July and August, during December, and during February (O/E: 13/21, 7/21, 8/20, and 15/21, respectively). Moreover, the relapse rate was high during autumn and spring (O/E: 84/62 and 72/61, respectively) and low during summer and winter (O/E: 45/61 and 47/64, respectively).
  
  
  CONCLUSIONS
  These data support the premise that there is seasonal variability in terms of relapses in ulcerative colitis patients and suggest that the role of seasonal triggering factors must be further investigated.
authors.affiliation: Department of Gastroenterology, Tzaneion General Hospital of Pireaus, Greece.
authors.forename: D G
authors.initials: DG
authors.lastname: Karamanolis
authors.forename: K C
authors.initials: KC
authors.lastname: Delis
authors.forename: G V
authors.initials: GV
authors.lastname: Papatheodoridis
authors.forename: E
authors.initials: E
authors.lastname: Kalafatis
authors.forename: G
authors.initials: G
authors.lastname: Paspatis
authors.forename: V C
authors.initials: VC
authors.lastname: Xourgias
mesh_terms: D015331:Cohort Studies; D003093:Colitis, Ulcerative / Q000453:epidemiology*; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012008:Recurrence; D012189:Retrospective Studies; D012621:Seasons; D013997:Time Factors