Article | Published:

Childhood body mass index and risk of inflammatory bowel disease in adulthood: a population-based cohort study

The American Journal of Gastroenterologyvolume 113pages694701 (2018) | Download Citation




The increasing incidence of inflammatory bowel disease (IBD) in western countries has led to the hypothesis that obesity-related inflammation could play a role in the etiology of IBD. However, this hypothesis lacks confirmation in studies of individuals prior to the typical onset of IBD in young adulthood.


In a cohort of 316,799 individuals from the Copenhagen School Health Records Register (CSHRR), we examined whether BMI at ages 7 through 13 years was associated with later IBD. Linking the CSHRR to the Danish National Patient Register, we identified cases of Crohn’s disease (CD) and ulcerative colitis (UC) diagnosed during follow-up. Cox regression was used to estimate the hazard ratios (HR) with 95% confidence intervals.


During 10 million person-years of follow-up, 1500 individuals were diagnosed with CD and 2732 with UC. At all examined ages, a 1 unit increase in BMI z-score was associated with a significantly decreased risk of UC (HRs = 0.9) and with a significantly increased risk of CD when diagnosed before age 30 (HRs = 1.2). We observed no associations between changes in BMI z-score between 7 and 13 years and later risk of CD or UC.


We found a direct association between childhood BMI and CD diagnosed before 30 years of age, and an inverse association between childhood BMI and UC irrespective of age. Our results support the previous hypotheses of obesity being a risk factor for CD, and suggest that childhood underweight might be a risk factor for UC.

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We are appreciative of the efforts required to build the CSHRR, which has been established in collaboration between the Institute of Preventive Medicine and the Copenhagen City Archive.

Author information


  1. Centre for Clinical Research and Prevention, Bispebjerg and Frederiksberg Hospital, Capital Region, Copenhagen,, Denmark

    • Camilla B. Jensen PhD
    • , Lars H. Ängquist PhD
    • , Jennifer L. Baker PhD
    •  & Tine Jess MD, DMSc
  2. Gastroenterology, Croydon University Hospital, Surrey, UK

    • Michael A. Mendall MD
  3. Department of Public Health, Section of Epidemiology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark

    • Thorkild I. A. Sørensen MD, DMSc
  4. The Novo Nordisk Foundation Centre for Basic Metabolic Research, Section on Metabolic Genetics, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark

    • Thorkild I. A. Sørensen MD, DMSc
    •  & Jennifer L. Baker PhD
  5. Department of Clinical Medicine, University of Aalborg, Aalborg, Denmark

    • Tine Jess MD, DMSc


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CBJ had full access to all data in the study and had the final responsibility for the decision to submit for publication.

Specific author contributions

CBJ and TJ conceived and designed the research; CBJ, LHÄ, and TJ conducted the research; CBJ, LHÄ, TJ, JLB, MAM, and TIAS analyzed data; CBJ and TJ wrote the article and had primary responsibility for final content. All authors read and approved the submitted article.

Financial support

This study was supported by Aase and Ejnar Danielsen’s foundation. The supporting bodies for this project had no role in the design, implementation, analysis, and interpretation of the data presented.

Potential competing interests

The authors declare that they have no conflict of interest.

Corresponding author

Correspondence to Camilla B. Jensen PhD.

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