Page 108 - The autoimmune hypothesis of narcolepsy and its unexplored clinical features M.S. Schinkelshoek

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Chapter 6
more mechanisms are described, that include a role for selective attention and the influence of transient awakenings (Harvey and Tang, 2012). Unfortunately, we were not able to include the effect of transient awakenings in our model.
Comparison of our findings on reverse sleep state misperception with other studies is challenging, since only few studies mention this type of sleep state misperception, almost exclusively during night time sleep in chronic insomnia (Attarian et al., 2004, Schneider-Helmert and Kumar, 1995, Trajanovic et al., 2007). It was proposed that increased alpha activity during sleep might play a role in reverse sleep misperception (Schneider-Helmert and Kumar, 1995, Schneider-Helmert, 2005).
Notably, dreaming was reported in a considerable amount of naps with only NREM sleep, consistent with extensive (nocturnal PSG) evidence on dreaming in NREM sleep with several studies disputing the paradigm of dreaming being confined to REM sleep (Aserinsky and Kleitman, 1953). Dream recall from NREM sleep stages is reported in 17.9% of NREM naps (both during night and day) in healthy males, while in only 51.2% of REM naps dream experiences were reported (Suzuki et al., 2004, Cavallero et al., 1992), broadly comparable with the percentages we found in this study. When dream perception was assessed only during daylight, it was also shown to be partly dissociated from REM sleep (Chellappa et al., 2009). Our results contribute to the notion that focusing on differences in dream content rather than crude dream perception between NREM and REM dreams might be more worthwhile in understanding the association between dreams and sleep physiology (Solms, 2000).
Our study design did not allow for a distinction between hypnagogic hallucinations, which people with narcolepsy may describe as a dream-like sensation in this context, and ‘normal’ dreams, since we only asked patients whether they dreamed or not. Theoretically, this might have led to an overestimation of the percentage of naps, both with and without SOREMP, in which patients reported to have dreamed.
Additionally, as reported before (Zhang et al., 2018), people with NT1 in this study have a shorter REM latency than other patients who have a SOREMP during MSLT. Also, the sleep stage sequences wake-REM and wake-N1-REM in the naps of the MSLT were found frequently in people with narcolepsy, in line with earlier findings (Marti et al., 2009, Ferri et al., 2016, Murer et al.,