This study investigated the correlations between subjective sleep assessed by the Oguri Shirakawa-Azumi (OSA) sleep inventory and objective indices based on electrocardiogram data obtained during sleep. Twenty-one sets of data were collected from 10 healthy women. As objective indices, total sleep time, sleep period time, sleep latency, and waking after sleep onset were assessed from polysomnogram data, and the averages of the power spectral indices of heart rate variability (HRV) -low frequency [LF], high frequency [HF] , ratio of LF to HF [LF/HF], and ratio of HF to the sum of LF and HF [HF/ (LF+HF) ]-were calculated. HF/ (LF+HF) showed positive correlations with four OSA factors : factor I (sleepiness), factor II (sleep maintenance), factor III (worries), and factor IV (integrated sleep feeling). Negative correlations were found between LF/HF and factors II, III, and IV. Although factor V (sleep initiation) had a negative correlation with length of sleep latency, no power spectral indices were correlated with this factor. The results suggest that some aspects of subjective sleep can be assessed by means of HRV power spectral indices.
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