Early-life animal exposure was not associated with risk of inflammatory bowel disease: a nationwide birth cohort study.

BACKGROUND AND AIMS: The incidence of inflammatory bowel disease (IBD) continues to rise globally. Early-life environmental exposures may influence immune development, but evidence regarding animal exposure remains inconsistent. We examined whether early-life exposure to pets or farm animals was associated with offspring risk of IBD in a prospective birth cohort.

METHODS

In this nationwide cohort study based on the Danish National Birth Cohort, prenatal offspring exposure to pets or farm animals, based on maternal reports, was used as the primary indicator of early-life animal exposure. Early-childhood exposure from birth to 18 months was examined in exposure-window analyses. Incident IBD, Crohn's disease (CD), and ulcerative colitis (UC) were identified through national registries. Associations were estimated using Cox proportional hazards models.

RESULTS

Among 90,306 offspring, 46% were prenatally exposed to pets and 7% to farm animals. During median follow-up of 24 years, 615 offspring developed IBD. Pet exposure was not associated with IBD risk (aHR 1.05, 95% CI 0.89-1.24), nor was farm animal exposure (aHR 1.00, 95% CI 0.73-1.37). Findings were consistent across specific animal categories and in analyses of CD and UC separately. In exposure-window analyses restricted to 63,958 offspring with maternal reports of both pre- and postnatal exposure, no associations were observed among offspring exposed only during pregnancy (aHR 1.10, 95% CI 0.75-1.63) or only during early childhood (aHR 0.73, 95% CI 0.46-1.15).

CONCLUSIONS

Early-life exposure to pets or farm animals was not associated with offspring risk of IBD. These findings suggest that early-life animal exposure may not be a major determinant of disease development.