Birth-cohort patterns in Crohn's disease and ulcerative colitis.
OBJECTIVE
To test the long-term time trends of mortality from inflammatory bowel disease (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), for the presence of birth-cohort phenomena.


METHODS
We analyzed mortality data from the national statistical offices of Canada, England and Wales, Italy, the Netherlands, Switzerland, and the USA for the past 60-80 years. Age-specific rates of death were plotted against the period of death, as period-age contours, and against the period of birth, as cohort-age contours.


RESULTS
In all six countries alike, the general time trends of IBD have been shaped by an underlying birth-cohort pattern. This pattern was also observed in the data of CD and UC analyzed separately. UC mortality increased in all generations born during the 19th century. It peaked among generations born shortly before the turn of the century and then decreased in all subsequent generations born throughout the 20th century. Compared with UC, the birth-cohort pattern of CD was delayed by 30-50 years.


CONCLUSIONS
In addition to one risk factor responsible for the general occurrence of IBD and possibly UC alone, there exists at least one additional risk factor responsible for CD. Exposure to both separate risk factors must occur during early life.
Division of Gastroenterology, Portland VA Medical Center, Oregon Health & Science University, Portland, Oregon, USA.
Amnon
A
Sonnenberg
D000328:Adult; D017677:Age Distribution; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D003093:Colitis, Ulcerative / Q000401:mortality*; D003424:Crohn Disease / Q000401:mortality*; D005060:Europe / Q000453:epidemiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009026:Mortality / Q000639:trends; D009656:North America / Q000453:epidemiology; D012307:Risk Factors; D013997:Time Factors; D055815:Young Adult