Is the change in Body Mass Index among youth newly diagnosed with type 1 diabetes mellitus associated with obesity at age 18?
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Abstract Background: Patients diagnosed with Type 1 diabetes mellitus (T1DM) require insulin therapy. Although necessary, insulin therapy is associated with an immediate increase in Body Mass Index (BMI). Excessive increase in BMI may lead to obesity, which is associated with both short and long-term negative health outcomes. The objective of this study was to determine whether weight change in the six months after diagnosis in children and adolescents with T1DM is related to obesity status at age 18. Methods: Data from the Diabetes Education Resource for Children and Adolescents database was used for this study. This unique database combines extensive clinical information on each patient with virtually universal coverage. The study population comprised all children 2-18 years old diagnosed with T1DM by DER-CA endocrinologists in Manitoba between 1997 and 2012 (N=377). BMI z- scores calculated from measured height and weight were used to classify BMI group membership using the 2000 Centers for Disease Control growth charts. Regression models were used to assess the association between change in BMI z-score six months after diagnosis, and BMI z-score at last visit prior to transfer to adult care. The models controlled for BMI z-score at diagnosis, sex, pubertal status and length of follow up. Additional stratified analyses examined sub-groups within the sample, to determine whether the effects were different for children with different characteristics (e.g. sex and pubertal status at diagnosis). Results: At diagnosis, 9% of the study cohort was underweight, 68% normal weight, 15% overweight and 8% obese. Most, (91%) but not all patients gained weight in the six months after T1DM diagnosis and initiation of insulin therapy. The pattern of weight change differed by BMI group at diagnosis, sex, and pubertal status. At last visit, average BMI z-scores for all groups of patients were above zero, and varied less than BMI z-scores at diagnosis. Results of the multivariate analytic model (adjusted R2= 0.56) show that BMI z-score at diagnosis was most important, followed by female sex, change in BMI z-score in the six months after diagnosis, the interaction between BMI z-score at diagnosis and change in BMI z-score in the six months after diagnosis, and duration of follow up. Conclusion: Results of this study demonstrate that patients’ BMI group, sex, and pubertal status at diagnosis influenced the pattern of their BMI z-score change in the six months after diagnosis, and thereafter. Diabetic care teams may need to monitor not only the amount of weight change in the period after T1DM diagnosis, but also consider BMI at diagnosis.