Sleep, waking and sleep inertia in sexual assault: A retrospective descriptive study

Women who wake from sleep during sexual assault commonly report confusion and disorientation. Confusion and disorientation, with impaired decision making after waking, are symptoms of 'sleep inertia', and part of the normal transition from sleep to full wakefulness which is maximal in the minutes after wakening and can be prolonged. In this study of 305 adult females (median age 26, range 18-68), who presented for a sexual assault forensic medical examination, 38 (12%) (median age 27, range 18-51) woke to find sexual acts already in progress. For 25 of these women (25/38 for 66%), an act of penile-vaginal penetration was already occurring when the woman woke. Of the 38 women (12%) who woke during the sexual assault, several had factors known to enhance the impairment of sleep inertia including forced arousal (38/38, 100%) and age under 25 (15/38, 39%). 17 (17/38 for 45%) of these women who woke had consumed varying amounts of alcohol prior to sleep and these 17 woke fully during the assault and then stayed awake. A further 16 women, (16/38 for 42%) woke during the sexual assault but returned to sleep during or after the assault, and all these 16 gave a history of intoxication by drugs or alcohol prior to sleep. Importantly 5, (5/38 for 13%) of the women who woke during the assault had consumed no intoxicating substances. A further 68 (23%) of the 305 women, (median age 26, range 18-58) had no memory on waking of the alleged sexual assault despite having other reasons to believe that a sexual assault had occurred. Forensic medical examiners can assist both the justice process, and patient care, by considering the possibility of sleep inertia among victims who report disorientation and slow or confused decision making on waking during a sexual assault.