Association between body mass index and age of disease onset with clinical outcomes in paediatric-onset Crohn's Disease (CD): a UK nation-wide analyses using the NIHR-IBD BioResource

Background: The relationship between adiposity and disease outcomes has never been investigated in paediatric Crohn's disease (CD). Aim: To investigate the relationship between a) body mass index (BMI) and clinical disease outcomes (hospitalisation, surgery, disease behaviour, biologic use and comorbidities) and b) the association between age of disease onset with clinical outcomes. Design: Outcomes were examined retrospectively in CD patients diagnosed at age <17 years. Data was obtained from the National Institute for Health Research IBD-UK BioResource. Subjects were categorised into normal BMI (<25kg/m(2)) and high BMI (>= 25 kg/m(2)). Age at disease diagnosis was categorised into pre-puberty/early puberty (<11 years), puberty (11-14 years) and post-puberty (15-17 years). Spearman rank correlation was used to test the associations between continuous variables and chi-square test was used to compare categorical variables. Results: 848 participants with CD were included, 51.8% males and a median age at diagnosis was 14 years. The median BMI measured at consent was 22.6 kg/m(2). Most of the participants (N= 605) had a BMI<25 kg/m(2 )with 243 (28%) participants having a BMI(3)25 kg/m(2). Those with high BMI were linked to a greater frequency of comorbidities (1 type of comorbidities: BMI(3)25= 20.6%; P=0.05 and >= 2 types of comorbidities: BMI(3)25= 8.6%; P=0.05, respectively). BMI and age at diagnosis showed a correlation with corticosteroid use (rho=-0.09, P=0.01 and rho=0.08, P=0.03, respectively). An early diagnosis (<11 years) was associated with complicated disease behaviour (p=0.01) and hospitalisation (P<0.001). Conclusions: A higher BMI and an earlier age of disease are associated with worse CD outcomes