Cross-sectional and longitudinal relationships of body mass index with glycemic control in children and adolescents with type 1 diabetes mellitus

Aims: Weight gain is an oft-cited outcome of improved glycemic control in adults with type 1 diabetes, though few studies have investigated this in youth. The purpose of this paper was to examine cross-sectional and longitudinal associations of body mass index (BMI, kg/m(2)) with glycemic control in youth with type 1 diabetes (n = 340, 12.5 +/- 1.7 year, 49% female, duration >= 1 year) participating in a 2-year multi-center intervention study targeting family diabetes management. Methods: BMI was calculated from height and weight measured at clinic visits. Glycohemoglobin (HbA1c) at each visit was assayed centrally. Cross-sectional associations of baseline BMI with glycemic control, and of change in BMI and HbA1c with baseline values, were examined. Longitudinal associations of time-varying BMI and HbA1c were examined using a multilevel linear mixed effects model controlling for time-varying time (months), insulin dose (units/kg/day), regimen, Tanner stage, and time invariant baseline diabetes duration, BMI, treatment group and sociodemographic characteristics. Results: Baseline HbA1c was unrelated to baseline BMI, but was related positively to subsequent BMI change (p = 0.04) and inversely to HbA1c change (p = 0.002). Baseline BMI was inversely related to BMI change (p = 0.01) and unrelated to HbA1c change. In multilevel regression, BMI was related inversely to HbA1c (%) (beta +/- SE = -0.11 +/- 0.02, p < 0.001) and positively to insulin dose (0.23 +/- 0.07, p = 0.001). In the treatment group only, BMI was positively related to pump regimen (0.18 +/- 0.08, p = 0.02). Conclusions: Increased insulin administered to improve glycemic control may contribute to increased BMI in youth with type 1 diabetes, indicating the importance of determining ways to minimize weight gain while optimizing glycemic control. Published by Elsevier Ireland Ltd.