Farming activities and risk of inflammatory bowel disease: a French nationwide population-based cohort study.

BACKGROUND AND AIMS: Epidemiological data regarding inflammatory bowel disease (IBD) are lacking, in particular for occupationally exposed populations. We investigated whether, among the entire French farm manager (FM) workforce, certain agricultural activities are more strongly associated with IBD than others.

METHODS: Nationwide population-based insurance claims and electronic health records from all FMs that worked at least once over the period 2002-2016 were used (n=1088561, 69% males). The outcome measure was the association between 26 farming activities and the risk of IBD, Crohn's disease (CD), and ulcerative colitis (UC), measured as hazard ratios (HRs), after adjusting for age, sex, pre-existing medical comorbidities, and farm location. The time to first chronic disease declaration was used as the underlying timescale. A model was generated for every activity and disease, utilizing a reference group comprising all FMs who abstained from the specified activity from 2002 to 2016.

RESULTS: There were 1752 IBD cases, with 704 CD (40.2%) and 1048 UC (59.8%) cases, respectively. Elevated HRs were observed for fruit arboriculture (HR from 1.17 to 1.52) and dairy farming (HR from 1.22 to 1.46) for all IBD, in crop farming for CD only (HR=1.26 [95CI%: 1.06-1.49]), and in shellfish farming (HR from 2.12 to 2.51) for both CD and IBD.

CONCLUSIONS: Further research regarding specific farming activities and exposures likely to modify the microbiota (e.g., pesticides, pathogens) is required to identify potential occupational risk factors (agricultural exposome) for IBD. Exposure to Mycobacterium avium subspecies paratuberculosis, cryptosporidium, environmental toxins, micro/nanoplastics, and pesticides represents promising research avenues.