Background: We aim to report the prevalence of irritable bowel syndrome (IBS) and elucidate the influence of IBS on the incidence of colorectal neoplasm through a community-screening-based, longitudinal follow-up study. Methods: We enroled 39 384 community residents aged 40 years or older who had participated in a community-based colorectal cancer-screening programme with an immunochemical faecal occult test since 1999. We followed a cohort that was free of colorectal neoplasm (excluding colorectal neoplasm at baseline) to ascertain the incident colorectal neoplasm through each round of screening and used a nationwide cancer registry. Information on IBS was obtained by linking this screened cohort with population-based health insurance claim data. Other confounding factors were also collected via questionnaire or biochemical tests. Results: The overall period prevalence of IBS was 23%, increasing from 14.7% for subjects aged 40-49 years to 43.7% for those aged 70 years and more. After controlling for age, gender and family history of colorectal cancer, screenees who had been diagnosed as having IBS exhibited a significantly elevated level (21%; adjusted hazard ratio (HR)=1.21 (95% CI: 1.02-1.42)) of incident colorectal adenoma compared with those who had not been diagnosed with IBS. A similar finding was noted for invasive carcinoma; however, the size of the effect was of borderline statistical significance (adjusted HR=1.20 (95% CI: 0.94-1.53)). Conclusions: IBS led to an increased risk for incident colorectal neoplasm.
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