Dreaming Characteristics in Non-Rapid Eye Movement Parasomnia and Idiopathic Rapid Eye Movement Sleep Behaviour Disorder: Similarities and Differences

Abstract

Background

Speech graph analysis (SGA) of dreams has recently shown promise as an objective and language-invariant diagnostic tool that can aid neuropsychiatric diagnosis. Whilst the notion that dreaming mentations reflect distinct physiologic processes is not new, such studies in patients with sleep disorders remain exceptionally scarce. Here, using SGA and other dream content analyses, we set to investigate structural and thematic differences in morning dream recalls of patients diagnosed with Non-Rapid Eye Movement Parasomnia (NREMP) and Idiopathic REM Sleep Behavior Disorder (iRBD).

Methods

A retrospective cross-sectional study of morning dream recalls of iRBD and NREMP patients was undertaken. Traditional dream content analyses, such as Orlinsky and Hall and Van de Castle analyses, were initially conducted. Subsequently, SGA was performed in order to objectively quantify structural speech differences between the dream recalls of the two patient groups.

Results

Comparable rate of morning recall of dreams in the sleep laboratory was recorded; 25% of iRBD and 18.35% of NREMP patients. Aggression in dreams was recorded by 28.57% iRBD versus 20.00% in NREMP group. iRBD patients were more likely to recall dreams (iRBD vs NREMP; P = 0.007), but they also had more white dreams, ie having a feeling of having dreamt, but with no memory of it. Visual and quantitative graph speech analyses of iRBD dreams suggested stable sequential structure, reflecting the linearity of the chronological narrative. Conversely, NREMP dream reports displayed more recursive, less stable systems, with significantly higher scores of graph connectivity measures.

Conclusion

The findings of our exploratory study suggest that iRBD and NREMP patients may not only differ on what is recalled in their dreams but also, perhaps more strikingly, on how dreams are recalled. It is hoped that future SGA-led dream investigations of larger groups of patients will help discern distinct mechanistic underpinnings and any associated clinical implications.

Keywords:

• dreams
• speech graph analysis
• NREM parasomnia
• REM behavior sleep disorder
• dream content analysis

Acknowledgments

This research was funded in whole or in part by the Wellcome Trust [103952/Z/14/Z]. For open access, the author IR has applied a CC BY public copyright licence to any Author Accepted Manuscript version arising from this submission.

This paper represents independent research in part funded by the NIHR Maudsley Biomedical Research Centre in South London and the Maudsley NHS Foundation Trust and King’s College London. The views expressed are those of the author(s) and not necessarily those of the NIHR or Department of Health and Social Care.

Disclosure

Dr David O’Regan reports that he has received honoraria for lectures, presentations and articles from Neurodiem, TEVA, British Association of Psychopharmacology and Idorsia. He is on the advisory panel for Redefining Education on Sleep Therapy. He has insomnia-related patents with Closed Loop Medicine, with whom he has stock options (as a former employee). He is the current president of the Sleep Medicine Section at the Royal Society of Medicine, London. The authors report no other conflicts of interest in this work.