Residential mobility and childhood inflammatory bowel disease: a nationwide case-control study.

Purpose: To examine the association of residential mobility, as a proxy for environmental influences, with childhood inflammatory bowel disease (IBD) risk.

Methods: Using nationwide register-based dataset, all 2038 IBD cases in Finland diagnosed at ages less than 15 years in 1992-2016 were individually matched by sex and age with five controls employing risk set sampling. Complete residential histories of the subjects were constructed from birth until the index date (diagnosis date of the case). Movement patterns were assessed by age, distance, and demographics of the departure and destination municipalities. Conditional logistic regression was employed to estimate the association between movements and IBD risk.

Results: Overall, residential movement was associated with a slightly decreased odds ratio (OR) for childhood IBD (OR 0.97, 95% confidence interval (CI) 0.95-1.00 for each movement). Further examination showed reduced ORs for moving to rural municipalities (OR 0.94, 95% CI 0.90-0.98) and to distances less than 50 km (OR 0.96, 95% CI 0.93-0.99). In disease subtype analyses, the effect mainly persisted in ulcerative colitis.

Conclusions: Our findings suggest lower childhood IBD risk associated with residential mobility. The effect was found in ulcerative colitis, but not in Crohn's disease. Movements to nearby and rural areas may reduce IBD risk, though this requires further investigation.