Measles, month of birth, and Crohn's disease

Background-The rise in the incidence of Crohn's disease (CD) suggests the r ole of an environmental factor in the development of the disease in suscept ible individuals. Perinatal exposure to infection has been proposed as such an environmental factor. Aim-To investigate the influence of birth date on the development of CD in later life. Patients and method-Four registers of patients with CD, diagnosed from 1972 to 1989, were combined, and data from 1624 patients were examined. The bir th dates of CD patients were compared with national birth figures for three decades (1941-50, 1951-60, and 1961-70) to avoid temporal changes in birth trends, and year of birth was compared with epidemic measles years between 1951 and 1967. Risk ratios with 95% confidence intervals (CI) and chi (2) tests were performed. Results-There were marginal differences between the birth dates of the CD p atients and those predicted from the general population. Further analysis o f both season of birth and year halves revealed a very weak association wit h the first half of the year (relative risk 1.14 (95% CI 1.01-1.30)), There was no association between developing CD and birth during measles epidemic s between 1951 and 1967. Conclusions-In utero or perinatal exposure to seasonal environmental factor s are unlikely potential aetiological agents in the later development of CD .