title: Date of birth in the occurrence of inflammatory bowel disease.
abstract: BACKGROUND
  It has been speculated that prenatal or perinatal exposure to infections affects the risk for developing inflammatory bowel disease (IBD). The aims of the study were to investigate the seasonal and monthly variations of birth dates among patients with Crohn's disease (CD) and ulcerative colitis (UC).
  
  
  METHODS
  The Hospital Episode Statistics (HES) comprises data of all patients admitted to hospitals in England. The data between April 1997 and March 2006 served to analyze birth dates of subjects with CD and UD, using the entirety of patients in the HES as controls.
  
  
  RESULTS
  Monthly birth dates were aggregated for the same months across consecutive birth years from January 1920 to December 1989 to determine whether a seasonal birth pattern existed among patients with CD and UC. No different seasonal birth patterns were observed between IBD patients and controls. A second analysis of individual months of birth, year after year, found that rates of births among IBD patients fluctuated from month to month. These fluctuations were different for CD and UC, with an overall weak correlation of r = 0.078, P = 0.018. There was a slight trend for stronger correlations to occur during more recent decades of birth, with r = 0.237 (P = 0.009) and r = 0.168 (P = 0.067) for the last 2 decades 1970-1979 and 1980-1989, respectively.
  
  
  CONCLUSIONS
  The patterns of birth dates among IBD patients do not support the contention that seasonally or monthly varying environmental factors during early childhood shape the subsequent risk of developing IBD.
authors.affiliation: Portland VA Medical Center, Portland, Oregon 97239, USA. sonnenbe@ohsu.edu
authors.forename: Amnon
authors.initials: A
authors.lastname: Sonnenberg
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003093:Colitis, Ulcerative / Q000453:epidemiology; D003424:Crohn Disease / Q000453:epidemiology; D005260:Female; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D011247:Pregnancy; D011295:Prenatal Care; D012307:Risk Factors; D012621:Seasons