Circadian control of heart rate in young insulin-dependent diabetes mellitus patients

Our objective was to determine whether young insulin-dependent diabetes mellitus (IDDM) patients without complications have abnormal circadian patterns of sympathetic or parasympathetic control of heart rate. Twenty-four-hour electrocardiographic recordings in 26 IDDM patients without complications and 27 control subjects were obtained. Patients were in good health and participated in their usual daily activities. Power spectral analysis was performed to determine the amount of heart rate variability due to all (0.01-1.0 Hz), low (0.04-0.15 Hz), and high (0.15-0.40 Hz) frequency input signals hourly and throughout the entire 24-h period, Overall 24-h heart rate power did not differ between control and IDDM subjects. In IDDM subjects high-frequency Bower decreased with increasing diabetes duration (r = -0.49, p = 0.013). A significant difference in circadian variation of heart rate power was only found for low frequency power (p = 0.014). These results demonstrate that young IDDM subjects without diabetic complications have normal or near normal parasympathetic and sympathetic circadian patterns of heart rate control.