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.