Rural and Urban Residence During Early Life is Associated with Risk of Inflammatory Bowel Disease: A Population-Based...

Area of Science:

• Epidemiology
• Gastroenterology
• Environmental Health

Background:

• Inflammatory bowel disease (IBD) encompasses Crohn's disease and ulcerative colitis, chronic conditions with increasing global incidence.
• The influence of environmental factors, including residential setting (rural vs. urban), on IBD risk is an area of ongoing research.
• Understanding geographical variations in IBD incidence may provide insights into etiological factors and inform public health strategies.

Purpose of the Study:

• To investigate the association between living in rural or urban households and the risk of developing inflammatory bowel disease (IBD).
• To examine this association at the time of diagnosis and during the first five years of life.
• To identify specific age groups and early-life exposures that may be most affected by the rural/urban environment regarding IBD risk.

Main Methods:

• Utilized population-based cohorts from four Canadian provinces, employing health administrative data to identify incident IBD cases.
• Classified residential status as rural or urban based on postal codes, considering population density and proximity to metropolitan areas.
• Calculated sex-standardized incidence rates and incident rate ratios (IRR) using Poisson regression, including analysis of a birth cohort for early-life exposure.

Main Results:

• A total of 6,662 rural and 38,905 urban IBD cases were identified. The incidence of IBD was slightly lower in rural residents (30.72 per 100,000) compared to urban residents (33.16 per 100,000), with an IRR of 0.90.
• A significant protective association between rural living and IBD risk was observed, particularly in younger age groups: children under 10 years (IRR 0.58) and adolescents aged 10-17.9 years (IRR 0.72).
• Analysis of the birth cohort revealed that continuous rural residence during the first 1-5 years of life was associated with a reduced risk of IBD (IRR 0.75-0.78).

Conclusions:

• Individuals residing in rural households exhibit a lower risk of developing inflammatory bowel disease (IBD).
• This protective association is notably stronger in pediatric and adolescent populations.
• Early-life exposure to a rural environment appears to be a significant factor in mitigating IBD risk.