Cohort Profile: The Christchurch IBS cOhort to investigate mechanisms FOr gut Relief and improved Transit (COMFORT)

Background and aims: This cross-sectional observational case-control study was initiated in July 2016 with the aim of increasing an understanding of the underlying disease mechanisms in functional gastrointestinal disorders (FGIDs) including irritable bowel syndrome (IBS), functional diarrhoea (FD), and functional constipation (FC). Specific areas of interest include the effect of food, microbiome, host and microbial genetics, metabolome, and psychological variables on unexplained chronic gastrointestinal (GI) symptoms. Methods: This study recruited consecutive patients who were attending one of two endoscopy centres in Christchurch, New Zealand, for colonoscopy and a subgroup of participants from the general public who did not undergo colonoscopy. Participants with known GI disease other than an FGID were excluded. Those with symptoms were recruited as cases, whilst those without symptoms were recruited as controls. In the days prior to preparation for colonoscopy, or an agreeable time for those not undergoing colonoscopy, demographic, symptom, psychological, dietary, and health data were collected in addition to biological samples (breath, faeces, blood, and urine). Colonic biopsies were taken at the time of colonoscopy from participants in the colonoscopy subgroup. Results: Between July 2016 and December 2018, 349 participants were recruited, 315 of whom completed the study, 220 participants were from the colonoscopy subgroup, and 95 from the non-colonoscopy subgroup. This included 129 controls and 186 cases (57 IBS-diarrhoea predominant, 30 IBS-constipation predominant, 41 IBS-mixed, 42 FC, and 16 FD). The mean age of FGID cases was 53.4 years and controls 54.4 years. Cases (149/186, 80.1%) and controls (57/72, 55.8%) were predominantly female. Education levels were similar across the cohort. Smoking and alcohol rates were also similar. Biological samples were collected as planned from participants. Conclusions: The COMFORT cohort is a unique clinical cohort of FGID cases and controls with a wide range of demographic, dietary, clinical, psychological, and health data in addition to biological samples. Future research will aim to use a systems biology approach to establish the potential role of diet, host-microbiome interactions, and other factors in the pathogenesis of FGIDs.