Disorders of Arousal and timing of the first period of slow wave sleep: Clinical and forensic implications

Abstract

The timing of first period of slow wave sleep (SWS) is often used as a proxy for determining if and when Disorders of Arousal (DOA) such as sleepwalking are likely to occur or did occur in the past. In criminal cases employing a "sleepwalking defense" the prosecution may argue that nocturnal violence or sexually aggressive behavior occurred too early in the sleep period to be associated with SWS. Expert witness opinion on the expected latency to SWS (LSWS) has varied from minutes after sleep onset to ≥60 min. A search of PubMed was conducted for LSWS and for any reports of DOAs occurring from stage N2. A total of 21 studies reported LSWS in normal controls, clinically diagnosed sleepwalkers, in otherwise normal sleepers following different types of sleep deprivation and due to the effects of alcohol. Five studies reported episodes of DOA from N2 sleep. The shortest mean LSWS of 6.4 min was found with a combination of total sleep deprivation and alcohol. In a group of normal research subjects, a LSWS mean of 10.7 min was noted. LSWS in DOA patients occurred as early as a mean of 12.4 min. Two sleep studies performed on Kenneth Parks, acquitted of the murder of his mother-in-law by a sleepwalking defense, reported LSWSs of 9.7 and 10 min. Sleep deprivation but not alcohol was found to decrease LSWS significantly. Expert opinions on LSWS should be based on scientific peer reviewed publications documenting empirical sleep evidence and can be much shorter than is generally reported.

Keywords: Alcohol; DOA, Disorder of Arousal; Disorder of arousal; Forensic evaluation; Kenneth parks; LSWS, Latency to Slow Wave Sleep; Latency to slow wave sleep; N3; NREM, Non-Rapid Eye Movement Sleep; SWS, Slow Wave Sleep; Sexual behavior in sleep; Sleep deprivation; Sleepwalking defense; Sleepwalking violence; Slow wave sleep.

Fig. 1

Four 30 s epochs originally published in the Rechtshaffen and Kales manual demonstrating the change from N2 sleep to N3sleep based on % of delta EEG waves [11]. Underlining indicates delta waves that met 75 uv. amplitude and 0.2–2.0 frequency. The top tracing appears in Figure 14 The other tracings appear in Fig. 2. The first 2 tracings have less than 20% delta EEG and are thus scored as Stage 2. The second 2 tracings have more than 20% delta EEG and are thus scored as stage 3.

Fig. 2

Standard visual scoring of sleep stages compared with slow wave activity (SWA) acquired at the same time for the same subject – in power in microvolts squared in the 0.5–4.0 hz frequency. Histograms are combined and modified from Fig. 1, Fig. 2, for subject S6 pages 533-4 in Janusko et al. [51]. Black arrows indicate timing of an episode of sleepwalking or confusional arousal. Red arrows indicated the start of N3 in the upper tracing and its relationship to SWA at the same time. SWA occurs prior to the onset of N3. Subject 6 is a clinically diagnosed with sleepwalking or confusional arousal with a mean age of 31.2 + 2.2 years. The subject was free of sleep disorders, kept a regular sleep/wake schedule, no psychotropic drug. Large arrows indicate SWA level at the time N3 is first scored.