Inverse coupling between ultradian oscillations in delta wave activity and heart rate variability during sleep

Clin Neurophysiol. 2001 Jun;112(6):992-6. doi: 10.1016/s1388-2457(01)00507-7.


Objective: We investigate the relationship between changes in heart rate variability and electroencephalographic (EEG) activity during sleep.

Method: Nine male subjects with regular non-rapid-eye movement-rapid-eye movement (NREM-REM) sleep cycles were included in the study. They underwent EEG and cardiac recordings during one experimental night. Heart rate variability was determined over 5-min periods by the ratio of low frequency to low frequency plus high frequency power [LF/(LF+HF)] calculated using spectral analysis of R-R intervals. EEG spectra were analyzed using a fast Fourier transform algorithm.

Results: We found an ultradian 80-120 min rhythm in the LF/(LF+HF) ratio, with high levels during rapid eye movement (REM) sleep and low levels during slow wave sleep (SWS). During sleep stage 2 there was a progressive decrease in the transition from REM sleep to SWS, and an abrupt increase from SWS to REM sleep. These oscillations were significantly coupled in a 'mirror-image' to the overnight oscillations in delta wave activity, which reflect sleep deepening and lightening. Cardiac changes preceded EEG changes by about 5 min.

Conclusions: These findings demonstrate the existence of an inverse coupling between oscillations in delta wave activity and heart rate variability. They indicate a non-uniformity in sleep stage 2 that underlies ultradian sleep regulation.

MeSH terms

  • Activity Cycles / physiology*
  • Adult
  • Analysis of Variance
  • Delta Rhythm* / methods
  • Heart Rate / physiology*
  • Humans
  • Sleep Stages / physiology*