HEART-RATE-VARIABILITY - SLEEP STAGE, TIME OF NIGHT, AND AROUSAL INFLUENCES

Spectral analysis was used to assess heart rate variability in consecu tive 5-min epochs during the night in 12 normal adults. Simultaneous t ime coding of EEC and digitized EKG allowed examination of heart rate variability as a function of sleep stage, time of night and presence o f EEG arousal. The results replicated previous studies in showing incr eases in high frequency components and decreases in low frequency comp onents of heart rate variability across NREM sleep stages and opposite changes in REM sleep and wake. These results are consistent with symp athetic nervous system activation during REM sleep and wake periods. T he shift in heart rate variability seen during REM sleep began in NREM sleep several minutes prior to standardly scored REM and often contin ued beyond the end of REM sleep. EEG arousals during Stage 2 and to sa me extent REM sleep were also associated with changes in heart rate va riability which were consistent with sympathetic activation, hn examin ation of beat to beat intervals in proximity to EEG arousals showed he art rate acceleration at least 10 beats prior to the EEG arousal. The arousal data along with Stage 2 sleep transition data support the cont ention that increases in central nervous system sympathetic activity p recede and possibly play a role in the initiation of REM sleep and aro usals during sleep. (C) 1997 Elsevier Science Ireland Ltd.