Anthropometric Trajectories in Children Prior to Development of Inflammatory Bowel Disease.

Importance: Poor nutrition and growth in childhood have short-term and long-term consequences, so understanding the timing of the onset of an impaired nutritional status is crucial for diagnosing and treating inflammatory bowel disease (IBD) at its earliest stage. Objective: To assess anthropometric trajectories before a pediatric diagnosis of IBD and growth recovery after diagnosis. Design, Setting, and Participants: This population-based cohort study included children born in Denmark from January 1, 1997, through December 31, 2015, with weight and length or height measurements at birth and at least 1 length or height and weight measurement at school age based on the Danish Medical Birth Register and the Danish National Child Health Register. Within this population, all individuals diagnosed with IBD at ages 5 to 17 years, according to the Danish National Patient Register, were identified. Data were analyzed from October 13, 2023, to April 17, 2024. Exposure: A pediatric diagnosis of IBD compared with the corresponding population without the disease. Main Outcomes and Measures: The outcome measures were z scores for length or height, weight, and body mass index (BMI [calculated as weight in kilograms divided by height in meters squared]) before and after pediatric IBD diagnosis compared with reference and sibling populations. Results: The final study population included 916 133 individuals (51.2% male) with a median of 3 pairs of length or height and weight measurements collected (IQR, 2-6 pairs). Of those, 1522 (median age, 14.3 years [IQR, 11.8-16.3 years]; 763 female [50.1%]) were diagnosed with IBD (851 [55.9%] with Crohn disease [CD] and 671 [44.1%] with ulcerative colitis [UC]). Compared with children without IBD, individuals with a later diagnosis of CD had declining anthropometric measures 3 years (weight: mean, -0.12 g [95% CI, -0.20 to -0.03 g]; BMI: mean, -0.13 [95% CI, -0.21 to -0.04]) and 1 year (length or height: mean, -0.20 cm [95% CI, -0.29 to -0.10 cm]) prior to diagnosis, whereas this was observed 1 year prior to a diagnosis of UC for weight (mean, -0.12 g [95% CI, -0.22 to -0.02 g]) and BMI (mean, -0.13 [95% CI, -0.23 to -0.03]). Deviating anthropometric patterns persisted after diagnosis, with the slowest recovery observed in children with CD. Conclusions and Relevance: The findings of this large-scale population-based cohort study of anthropometrics in children suggest impaired nutritional status as assessed by weight up to 3 years and by length or height 1 year before a diagnosis of CD and by weight up to 1 year before a diagnosis of UC. These findings emphasize that the onset of pediatric IBD may occur years prior to diagnosis, that growth recovery may first occur after diagnosis and treatment, and that frequent nutritional screenings may help ensure a healthy transition to adulthood.