Polysomnography Findings in Nightmare Disorder: A Systematic Review and Meta-Analysis Protocol

Polysomnographic sleep architecture in individuals suffering from idiopathic nightmares exhibits distinct alterations, particularly within rapid eye movement (REM) parameters, though broader metrics remain inconsistent across clinical literature. Nightmare disorder, classified as a type of parasomnia within the International Classification of Sleep Disorders, features recurring, vivid, and intensely distressing dreams recalled predominantly upon awakening during the latter half of a sleep episode. These episodes trigger significant daytime functional impairments across occupational, social, and educational domains, while serving as established clinical indicators for the progression of major depressive disorder, anxiety disorder, and posttraumatic stress disorder. To clarify the underlying pathophysiology of these disturbances, researchers registered a systematic review protocol on PROSPERO under ID CRD42024582896, adhering to PRISMA guidelines to synthesize existing polysomnography data.

Key Clinical Takeaways

• Idiopathic nightmares disrupt standard sleep architecture, primarily affecting rapid eye movement parameters and emotional processing pathways during REM sleep.
• Researchers conducted systematic literature searches across MEDLINE, EMBASE, all EBM databases via OVID, and Web of Science to evaluate objective polysomnographic variables against healthy controls.
• While subjective distress is well-documented, objective polysomnographic findings regarding total sleep time and N1 percentage remain varied across existing studies due to methodological and demographic differences.

Pathophysiological Mechanisms and Rapid Eye Movement Alterations

The development of idiopathic nightmares is mechanically tied to disrupted fear extinction and faulty emotional processing during rapid eye movement sleep. Because these markers point toward specific alterations in rapid eye movement parameters, researchers position these variables as potential objective biomarkers for nightmare disorder. Polysomnography operates as the clinical gold standard for evaluating these sleep dynamics. However, historical data examining total sleep time and N1 sleep percentages present notable inconsistencies across independent cohorts. Some investigations highlight prolonged rapid eye movement percentages and delayed rapid eye movement latency, while others fail to replicate these findings in isolated nightmare populations.

Power spectral analysis further demonstrates objective physiological shifts. Specific studies cited within the review note elevated high alpha power during rapid eye movement sleep among affected individuals, whereas alternative analyses document altered slow-theta activity when compared against healthy control groups. These discrepancies largely stem from variations in demographic characteristics, clinical features, and experimental methodologies, establishing the clear necessity for a comprehensive quantitative synthesis of polysomnography findings.

Methodology and Systematic Review Parameters

Independent reviewers executed systematic literature searches initially on September 9, 2024, followed by updated searches between October 20 and December 13, 2025, across MEDLINE, EMBASE, OVID EBM databases, and Web of Science. Search strings combined terms relating to nightmares with specific sleep monitoring terminology, including polysomnography, sleep architecture, and sleep stages. Two independent reviewers screened citations, resolving discrepancies through consultation with a senior author.

The review established rigorous inclusion criteria, requiring diagnosed nightmare disorder based on official diagnostic manuals and the inclusion of a healthy control group with comparative polysomnography variables published in English. Studies featuring participants with concurrent neurological or psychiatric disorders—such as posttraumatic stress disorder, major depressive disorder, or anxiety disorder—were systematically excluded to isolate idiopathic presentations. Case reports, animal studies, reviews, and abstracts lacking direct polysomnography comparisons were similarly filtered out to preserve data integrity.

Clinical Implications for Sleep Medicine

Identifying objective sleep features through rigorous meta-analytic evaluation improves the overall clinical management of parasomnias. By isolating true pathophysiological markers from confounding demographic variables, sleep specialists can better differentiate idiopathic nightmare disorder from secondary sleep disturbances tied to underlying mood or anxiety disorders. Patients experiencing persistent, distressing sleep disruptions that impair daily functioning are encouraged to consult qualified sleep medicine physicians or clinical psychologists specializing in behavioral sleep medicine for comprehensive evaluation and evidence-based interventions.

Disclaimer: The information provided in this article is for educational and scientific communication purposes only and does not constitute medical advice. Always consult with a qualified healthcare provider regarding any medical condition, diagnosis, or treatment plan.