Awakening thresholds in sleepwalkers and controls: Effects of experimental auditory stimuli and sleep deprivation

Abstract

It has been suggested that sleepwalkers are more difficult to fully awaken from sleep than controls. However, no quantified comparisons have been made between these two populations. The present study assessed the effects of auditory stimuli (AS) in sleepwalkers and controls during normal and recovery sleep. Ten adult sleepwalkers and ten controls were investigated. Participants were presented with AS during slow-wave sleep (SWS), REM and stage 2 sleep either during normal or recovery sleep following 25hr of sleep deprivation. In the targeted sleep stage, 3sec AS were presented at 1min intervals in ascending intensities (40dB to 90dB) until an awakening (including awakenings and/or sleepwalking) or a maximum of 6 AS was reached. When compared to controls, sleepwalkers had a significantly higher mean intensity of AS (in dB) that induced awakenings during normal REM sleep, a significantly lower mean percentage of AS that induced awakenings during normal REM sleep, and a significantly higher mean percentage of AS that induced awakenings during recovery SWS. When compared to normal sleep, recovery sleep resulted in a significantly higher percentage of AS that induced arousals in both groups, and a significantly higher percentage of AS that induced awakenings in sleepwalkers during REM sleep. There were no other significant group or sleep period differences for the mean percentage of AS or mean intensity of AS that induced awakenings. The data suggest that sleepwalkers have a higher auditory awakening thresholds compared to controls but only during normal REM sleep.