Effects of Birth Cohorts on the Irritable Bowel Syndrome Support Early-Life Risk Factors

Background: Irritable bowel syndrome (IBS) is common with prevalence reported between 10 and 20 %. IBS clusters in families but it is unknown whether this is explained by a common environment, genes, or both. If early-life factors are important, IBS might be expected to demonstrate a birth cohort phenomenon. Aim: To investigate whether there is a birth cohort phenomenon for subjects with IBS. Methods: Validated questionnaires were sent to a random sample of Olmsted County, Minnesota, residents who recorded gastrointestinal symptoms; IBS diagnosis was based on the modified Rome criteria. Birth cohorts were chosen a priori based on historical national trends in birth weights using 10-year increments. Logistic regression was used to develop odds ratios to assess the association of IBS with calendar period, birth cohort, age, gender, and somatic symptom score. Results: A total of 4,893 surveys were completed with an overall survey response rate of 58 %. The survey responders were between 25 and 94 years of age and 53 % were female. The overall prevalence of IBS was 16.2 % (95 % CI 15.3–17.4). The univariate association of IBS with birth cohort was significant (p < 0.001) as was the association adjusted for age and gender. The prevalence of IBS was highest for the birth cohort 1963–1972 with an odds ratio of 2.6 (95 % CI 0.97–7.0, p = 0.058). Conclusions: Population-based data support a possible birth cohort phenomenon in IBS. If correct, early-life risk factors likely play a key role in the development of IBS.