title: Ubiquitous occurrence of birth-cohort patterns in inflammatory bowel disease.
abstract: OBJECTIVE
  The aim of the present study was to demonstrate the ubiquitous occurrence of the birth-cohort phenomenon of inflammatory bowel disease among US whites and nonwhites, as well as males and females.
  
  
  METHODS
  Mortality from Crohn's disease and ulcerative colitis in the USA between 1950 and 2010 were analyzed to discern underlying birth-cohort patterns affecting both their time trends. Age-standardized cohort mortality ratio was used as a summary statistic to represent the overall mortality associated with consecutive birth-cohorts.
  
  
  RESULTS
  The cohort-age contours of Crohn's disease aligned to form one hyperbola with an initial rise between 1865 and 1935 and a subsequent decline. This pattern was confirmed by the time trends of the corresponding standardized cohort mortality ratio values. In ulcerative colitis, the individual cohort-age contours also aligned into one hyperbola that appeared shifted towards earlier generations by about 30 years when compared with Crohn's disease. Similar trends were observed in men and women or whites and nonwhites analyzed separately.
  
  
  CONCLUSIONS
  The birth-cohort patterns indicate that exposure to two separate risk factors must have occurred in both diseases during an early period of life. In the USA, these exposures have changed over historical times similarly in both sexes and different ethnic groups.
authors.affiliation: Portland VA Medical Center and the Oregon Health and Science University, Portland, Oregon, USA.
authors.forename: Amnon
authors.initials: A
authors.lastname: Sonnenberg
mesh_terms: D015331:Cohort Studies; D003093:Colitis, Ulcerative / Q000208:ethnology / Q000209:etiology / Q000401:mortality; D003424:Crohn Disease / Q000208:ethnology / Q000209:etiology / Q000401:mortality; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007231:Infant, Newborn; D015212:Inflammatory Bowel Diseases / Q000208:ethnology / Q000209:etiology / Q000401:mortality*; D008297:Male; D009026:Mortality / Q000639:trends; D012307:Risk Factors; D012737:Sex Factors; D014481:United States / Q000453:epidemiology; D044465:White People / Q000706:statistics & numerical data