Correlation between electroencephalography and heart rate variability during sleep

Abstract

It is known that autonomic nervous activities change in correspondence with sleep stages. However, the characteristics of continuous fluctuations in nocturnal autonomic nerve tone have not been clarified in detail. The study aimed to determine the possible correlation between the electroencephalogram (EEG) and autonomic nervous activities, and to clarify in detail the nocturnal fluctuations in autonomic nerve activities. Overnight EEGs and electrocardiograms of seven healthy males were obtained. These EEGs were analyzed by fast Fourier transformation algorithm to extract delta, sigma and beta power. Heart rate and heart rate variability (HRV) were calculated in consecutive 5-min epochs. The HRV indices of low frequency (LF), high frequency (HF) and LF/HF ratio were calculated from the spectral analysis of R-R intervals. The sleep stages were manually scored according to Rechtschaffen and Kales' criteria. Low frequency and LF/HF were significantly lower during non-rapid eye movement (NREM) than REM, and were lower in stages 3 and 4 than in stages 1 and 2. Furthermore, delta EEG showed inverse correlations with LF ( r = -0.44, P < 0.001) and LF/HF ( r = -0.41, P < 0.001). In contrast, HF differed neither between REM and NREM nor among NREM sleep stages. Detailed analysis revealed that correlation was evident from the first to third NREM, but not in the fourth and fifth NREM. Delta EEG power showed negative correlations with LF and LF/HF, suggesting that sympathetic nervous activities continuously fluctuate in accordance with sleep deepening and lightening.

Sleep and autonomic nervous system changes – enhanced cardiac sympathetic modulations during sleep in permanent night shift nurses

“…The findings of this study suggested that nighttime workers would seem to have higher cardiac sympathetic regulations attributable to long-term night shift working, which may explain why they have been found to have higher rates of cardiac disorders. Sleep assigned according to a predetermined laboratory schedule can sometimes fail to reflect the habitual sleeping time (27)(28)(29). Our design allowed nurses to sleep spontaneously in their own beds, in privacy, and according to their flexible night shift sleeping schedule.…”

A prominent role for amygdaloid complexes in the Variability in Heart Rate (VHR) during Rapid Eye Movement (REM) sleep relative to wakefulness

“…For instance, EEG power spectral density relates to VHR indices (Otzenberger et al, 1997(Otzenberger et al, , 1998Ehrhart et al, 2000;Brandenberger et al, 2001;Ako et al, 2003). However, the cerebral correlates of VHR during sleep needs to be further characterized, anatomically refined and described separately for NREMS and REMS.…”

Guidelines for the Recording and Evaluation of Pharmaco-Sleep Studies in Man: The International Pharmaco-EEG Society (IPEG)

“…Period amplitude analysis has been applied and compared with power spectral analysis for all-night recordings [194]. The investigation of the correlation between spectral EEG activity and heart rate variability during sleep shows that sympathetic nervous system activity continuously fluctuates in accordance with sleep deepening and lightening [195]. Finally, by comparing the predicted rhythm to the actual EEG at each sample with the rhythm of the previous one in specific frequency ranges, it is possible to construct microcontinuity parameters with physiological implications sensitive to sleep and less sensitive to artefacts [196].…”