Heart rate variability during waking and sleep in healthy males and females

Objectives: The study goal was to investigate autonomic activity with heart rate variability analysis during different sleep stages in males and femal es. Design: The study utilized a 2 Groups (males, females) X 4 States (waking, stage 2 sleep, stage 4 sleep, rapid-eye movement sleep) mixed design with o ne repeated, within-subjects factor (i.e., state). Setting: The study was carried out in the sleep laboratory of the Thomas N. Lynn Institute for Healthcare Research. Participants: Twenty-four healthy adults (fourteen females and ten males). Interventions: NA Measurements and Results: All participants underwent polysomnographic monit oring and electrocardiogram recordings during pre-sleep waking and one nigh t of sleep. Fifteen-minute segments of bleat-to-beat heart rate intervals d uring waking, stage 2 sleep, stage 4 sleep, and REM sleep were subjected to spectral analysis. Compared to NREM sleep, REM sleep was associated with d ecreased high frequency (HF) band power, and significantly increased low fr equency (LF) to (HF) ratio. Compared to females, males showed significantly elevated LF/HF ratio during REM sleep. Males also demonstrated significant ly decreased HF band power during waking when compared to females. No signi ficant sleep- or gender-related changes in LF band power were found. Conclusions: The results confirmed changes in autonomic activity from wakin g to sleep, with marked differences between NREM and REM sleep. These chang es were primarily due to stage-related alterations in vagal tone. REM sleep was characterized by increased sympathetic dominance, secondary to vagal w ithdrawal. The data also suggested gender differences in autonomic function ing during waking and sleep, with decreased vagal tone during waking and in creased sympathetic dominance during REM sleep in the males.