Objective Cardiovascular complications of diabetes mellitus are mostly present in adult patients, but subclinical signs of autonomic neuropathy may be demonstrated already after shorter duration of diabetes in adolescents. The aim of the present study was to detect cardiovascular autonomic dysfunction in adolescent diabetes mellitus by the use of heart rate variability (HRV) analysis.
Methods Twenty type 1 diabetes mellitus patients were enrolled in the study (age 14,1±1,8 years, duration of diabetes 7,8±3,8 years). Twenty healthy children served as controls (14,2±0,5 years). HRV and 24 hour blood pressure monitoring were performed by a Cardiotens device (Meditech, Budapest).
Results The daytime average blood pressure was not different in the two groups, but the nighttime diastolic blood pressure was higher in the diabetic group. The diurnal changes of blood pressure were decreased in diabetics compared to healthy adolescents. The time and frequency domain analysis of HRV spectrum revealed no difference between the diabetic and control groups when 24 hour curves were analyzed. By separated analysis of nighttime measurements we could demonstrate a decreased high frequency (HF) spectrum density in the diabetes group, indicating decreased parasympathetic activity. The LF/HF ratio was higher in the diabetes group. There was a significant correlation between the diurnal blood pressure changes and LF/HF ratio.
Conclusions We conclude that decreased nighttime parasympathetic activity found in several diabetic patients indicates autonomic neuropathy. We propose the analysis of the nighttime HRV measurements for the detection of diabetic autonomic neuropathy.