Published online Dec 21, 2013. doi: 10.3748/wjg.v19.i47.9063
Revised: September 12, 2013
Accepted: September 29, 2013
Published online: December 21, 2013
AIM: 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.
CONCLUSION: Our results suggest that environmental factors associated with winter and spring seasonality may be responsible for triggering the clinical onset of UC in Japan.
Core tip: Monthly seasonality in the symptomatic onset of ulcerative colitis (UC) during October and March was observed in Japan. The onset of symptoms frequently occurred during the winter, whereas relapse of UC particularly occurred in October. Upper respiratory inflammation was one of the main factors responsible for relapse. Therefore, environmental factors associated with winter and spring seasonality may be responsible for triggering the clinical onset of UC in Japan.