Higher body mass index predicts cardiac autonomic dysfunction: A longitudinal study in adolescent type 1 diabetes.

BACKGROUND: Obesity is associated with an increased risk of cardiovascular morbidity in adults with diabetes. OBJECTIVE: To examine the predictive role of body mass index (BMI) and adiposity on cardiac autonomic function in childhood onset type 1 diabetes. SUBJECTS: Two hundred and fifty-three participants with type 1 diabetes (aged 8-30 years) were assessed for diabetes complications at a tertiary hospital, and followed over 7 years (total 922 visits). METHODS: Heart rate variability (HRV) measures assessed by 10-minute electrocardiography recording using LabChart Pro were standard deviation of RR intervals, time between consecutive QRS complexes, [SDNN], root mean squared difference of successive RR intervals (RMSSD), triangular index (TI), and low to high frequency ratio [LF:HF]. Multivariable generalized estimating equations were used to model the longitudinal associations between HRV measures and clinical variables (BMI standard deviation scores [SDS], waist:height ratio, total daily insulin dose/kg (TDD) and hemoglobin A1c [HbA1c]). RESULTS: At baseline, mean age was 14.4 ± 2.7 years, diabetes duration 7.1 ± 3.7 years, HbA1c 8.3% ± 1.5% (67 ± 16 mmol/mol), and 33% were overweight/obese (BMI ≥85th percentile). At final visit, mean age was 18.5 ± 2.7 years, duration 11.3 ± 3.9 years, HbA1c 9.0% ± 1.8% (75 ± 20 mmol/mol), and 40% were overweight/obese. Adiposity (higher BMI SDS or waist: height ratio) was a significant predictor of worse HRV (lower SDNN, RMSSD; P < .05), while higher HbA1c and TDD predicted all adverse HRV measures (lower SDNN, RMSSD, TI; P < .05) and abnormal sympathovagal balance (higher LF:HF ratio; P < .05). CONCLUSIONS: Higher BMI and central adiposity are associated with cardiac autonomic dysfunction in childhood onset type 1 diabetes, after adjusting for HbA1c. Interventions targeting overweight/obesity during adolescence may optimize long-term vascular health in type 1 diabetes.

Heart rate variability in pubertal girls with type 1 diabetes: its relationship with glycaemic control, insulin resistance and hyperandrogenism.

OBJECTIVE: To examine the association between glycaemic control, insulin resistance and hyperandrogenism on cardiac autonomic function in peripubertal girls with type 1 diabetes. DESIGN: Prospective, clinic-based study of 125 girls with diabetes and 46 age-matched nondiabetic girls. MEASUREMENTS: Heart rate variability (HRV) parameters derived from a 10-min ECG recording using LabChart Pro were as follows: standard deviation of mean NN intervals (SDNN), where NN = adjacent QRS complexes; root mean squared difference of successive NN intervals (RMSSD) - estimates of overall HRV; and low-/high-frequency (LF:HF) ratio - an estimate of the sympathovagal balance. Androgens and sex hormone binding globulin (SHBG) were measured in girls with diabetes, and free androgen index (FAI) calculated. HRV and anthropometry were measured in nondiabetic controls. RESULTS: Adolescents with diabetes (median age 15·1 years [13·3-16·0], diabetes duration 7·0 years [4·6-10·0] and median HbA1c 8·4% [7·5-9·3]) had higher HR and lower HRV compared with controls. Using multivariate models in the diabetes group, higher HR was associated with higher HbA1c, total daily dose insulin/kg body weight and systolic BP standard deviation scores (SDS), whilst reduced HRV was associated with higher HbA1c (SDNN, RMSSD and LF:HF ratio), lower SHBG (SDNN and RMSSD) and higher weight SDS (LF:HF ratio). Higher FAI was associated with higher HR and reduced HRV measures in the univariate analyses only. CONCLUSIONS: In adolescent girls with diabetes, reduced HRV parameters are associated with worse glycaemic control, lower SHBG and higher weight SDS. SHBG should be considered in the cardiac risk models for this population.

Unexpected Management Behaviors in Adolescents With Type 1 Diabetes Using Sensor-Augmented Pump Therapy.

BACKGROUND: Continuous glucose monitoring can improve glycemic outcomes in individuals with type 1 diabetes. However, the constant exposure to real-time glucose levels can sometimes lead the individual to make some risky choices to address the glycemic excursions. Hence, the purpose of this study was to explore the aberrant management behaviors of youth with type 1 diabetes on sensor-augmented pump therapy (SAPT). METHODS: Participants in a clinical trial using SAPT on Medtronic MiniMed™ 640G pump who experienced deteriorating glycemic control or unexplained hypoglycemia were identified by the health care professional. The pump and/or sensor data uploaded to CareLink™ Therapy Management Software were reviewed in these participants. RESULTS: Uncharacteristic management behaviors were identified in five adolescent males. Continuous exposure to high glucose levels resulted in obsessive behaviors displaying a perfectionistic attitude in two participants. Multiple boluses were delivered frequently as uneaten carbohydrates in participant 1 while participant 2 resorted to delivery of extra insulin by cannula fills. In contrast, participant 3 chose to remain hyperglycemic to avoid weight gain while participant 4 trusted the system and used sensor glucose readings for calibrations, with resultant deterioration in glycemic control in both participants. On the other hand, participant 5, due to mistrust in the pump suspend function, consumed carbohydrates with downward glucose trends with rebound hyperglycemia. CONCLUSIONS: Constant exposure to real-time data can lead to unsafe management responses in adolescents with the behavior influenced by trust or mistrust in the system. Adolescents should be empowered with problem-solving strategies for safe management.