Temporal relationship between dynamic heart rate variability and electroencephalographic activity during sleep in man.

In previous sleep studies, it has been demonstrated that Poincare plots of RR intervals, which provide a beat to beat dynamic measure of heart rate variability, have distinctive and characteristic patterns according to sleep stages. This study was designed to evaluate the temporal relationship between heart rate variability and sleep electroencephalographic activity (EEG) by using the Pearson's interbeat autocorrelation coefficients of RR intervals derived from the Poincare plots. The coefficients were calculated in 12 subjects over each minute and were related to the profiles of EEG mean frequency (0.5-35 Hz) computed using a Fast Fourier Transformation algorithm. Overnight profiles of interbeat autocorrelation coefficients and of EEG mean frequency were found to be related with highly significant cross-correlation coefficients ranging between 0.216 and 0.638 (P < 0.001). The variations in heart rate variability preceded changes in brain activity by 1-2 min. These results demonstrate that beat to beat heart rate variability and EEG activity are closely linked during sleep in normal man.