Features of Electroencephalographic Changes and Autonomic Nervous Activity during Sleep Onset Period of the Patients with Difficulty Falling Asleep

Abstract

  Evaluation of sleep onset difficulty by polysomnography with the standard sleep stage criteria by Rechtschaffen and Kales often shows that sleep problem marked by difficulty falling asleep shares the same structure as normal sleep onset period (SOP). This study aimed to clarify whether objective features during SOP of the patients with difficulty falling asleep were different from those of normal control. Objective criteria established for the nine electroencephalogram (EEG) stages and autonomic nervous activity were used to confirm subjective complaints of difficulty falling asleep. Both of psychophysiological insomnia (PPI) and normal control group had 7 participants each. As a result, the PPI group showed significantly longer latencies of each EEG stage from H4 to H8 and longer durations of H2, H3, and H5 than the normal control group. Additionally, higher mean LF/HF ratios, indicating sympathetic nervous activity, were observed at the time of each EEG stage's first appearance during SOP in the PPI group. Our results may indicate the combination of indices used in this study could reflect the more detailed changes inherent in the sleep onset process and contribute to investigate subjective difficulty falling asleep.