HUMAN HEART-RATE-VARIABILITY AND SLEEP STAGES

With the aim of better understanding the dynamic changes in sympatho-v agal tone occurring during the night, human heart rate variability (HR V) during the various sleep stages was evaluated by means of autoregre ssive spectral analysis.Each recording consisted of an electroencephal ogram, an electrooculogram, and electromyogram, an electrocardiogram, and a spirometry trace. All of the data were sampled and stored in dig ital form. Sheep was analysed visually, but HRV was analysed off-line by means of original software using Burg's algorithm to calculate the LF/HF ratio (LF: 0.04-0.12 Hz; HF: 0.15-0.35 Hz) for each sleep stage. Seven healthy subjects (four males; mean age 35 years) were enrolled in the study. Our findings show a progressive and significant reductio n in the LF/HF ratio through sleep stages S1-S4, as a result of an inc rease in the HF component; this indicates the prevalence of parasympat hetic activity during slow-wave sleep. During wakefulness, S1 and REM, the LF/HF values were similar and close to 1.