Abstract
We have estimated the sleep stages by using heart rate variability. Polysomnographic monitoring was performed in five healthy subjects, aged between 26-27 years. Electrocardiogram (ECG) and respiratory data were analyzed for every 30 seconds interval by using Least Square Cosine Spectrum Method. To make quantitative analysis of respiratory pattern during sleep, we have developed an index derived from heart rate variability (HRV) and referred to as "RA (Rhythm Adaptability)". The RA of respiration showed positive correlations with the RA of heart rate. The RA of heart rate showed 90-minutes rhythm during sleep, and positive correlations with electroencephalogram (EEG) power in delta and theta waves (P<0.001). The RA was lower during REM sleep and WAKE, and was higher during sleep stages 3 and 4. We confirmed that the RA might be useful parameter for the evaluation of sleep stages.
