sleep stage 4

• sleep stages

All statements concerning non-REM sleep stage 3 apply to stage 4 except that high voltage, EEG slow waves persist in 50% or more of the epoch; non-REM sleep stage 4 usually represents12-15% of total sleep time. Sleepwalking, sleep terrors, and confusional arousal episodes generally start in stage 4 or during arousals from this stage. See Sleep Stage 3.