CIRCADIAN CONTROL OF HEART-RATE IN YOUNG INSULIN-DEPENDENT DIABETES-MELLITUS PATIENTS

Our objective was to determine whether young insulin-dependent diabete s mellitus (IDDM) patients without complications have abnormal circadi an patterns of sympathetic or parasympathetic control of heart rate. T wenty-four-hour electrocardiographic recordings in 26 IDDM patients wi thout complications and 27 control subjects were obtained. Patients we re in good health and participated in their usual daily activities. Po wer spectral analysis was performed to determine the amount of heart r ate 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 enti re 24-h period, Overall 24-h heart rate power did not differ between c ontrol and IDDM subjects. In IDDM subjects high-frequency Bower decrea sed with increasing diabetes duration (r = -0.49, p = 0.013). A signif icant difference in circadian variation of heart rate power was only f ound for low frequency power (p = 0.014). These results demonstrate th at young IDDM subjects without diabetic complications have normal or n ear normal parasympathetic and sympathetic circadian patterns of heart rate control.