Modified autonomic balance in offsprings of diabetics detected by spectral analysis of heart rate variability

This study was performed to evaluate the influence of family history for non–insulin-dependent diabetes mellitus (NIDDM) on autonomic balance. The latter was assessed by spectral analysis of heart rate variability (SA-HRV) and by analyzing the relative contribution of low-frequency (LF) and high-frequency (HF) components. Twenty glucose normotolerant offsprings of NIDDM parents and 20 controls underwent a 1-hour continuous electrocardiogram (ECG). LF and HF (mean 6 SEM in normalized units [NU]), respectively increased and decreased in offspring versus controls. The LF/HF ratio (mean 6 SEM) significantly increased (LF/HF 5 3.25 6 0.7 v 1.45 6 0.5, P < .0001 offsprings v controls). To test a stimulated response, a passive tilting (1 90°) after 30 minutes of bed rest (0°) was performed in a subsample of subjects (10 offsprings v 10 controls). During bed rest, we found significantly higher values of the LF/HF ratio in offsprings versus controls (1.93 6 0.3 v 1.08 6 0.2, P < .05), whereas in the head-up position, the LF/HF ratio value increased to the same levels in the 2 groups (6.48 6 1.3 v 6.89 6 1.4, not significant [NS]). NIDDM family history is characterized in the basal condition by an imbalance of the autonomic system, which, compared with controls, is expressed by a higher weight of sympathetic and a lower weight of parasympathetic components. No significant differences can be found under stimulated conditions.