Reduced Rapid Eye Movement Density in Parkinson Disease: A Polysomnography-Based Case-Control Study

Area of Science:

• Neurology
• Sleep Medicine
• Neuroscience

Background:

• Excessive daytime sleepiness is a common symptom in idiopathic Parkinson disease (IPD).
• Current methods for assessing sleepiness in IPD may not fully capture the underlying pathophysiology.
• Rapid eye movement (REM) sleep is a critical stage of sleep, and its characteristics may be altered in neurodegenerative conditions.

Purpose of the Study:

• To investigate rapid eye movement density (RD) in patients with IPD.
• To determine if RD can serve as a surrogate marker for excessive daytime sleepiness in IPD.
• To explore the relationship between RD and other sleep parameters and subjective sleep quality in IPD patients.

Main Methods:

• A retrospective polysomnography study was conducted on 81 subjects, including early-stage IPD, middle-stage IPD, and healthy controls (HC).
• RD was calculated as the number of ocular movements per minute of REM sleep.
• Patients and controls completed validated sleepiness questionnaires, including the Parkinson's Disease Sleep Scale (PDSS) and the Nonmotor Symptoms Questionnaire (NMSQuest).

Main Results:

• RD was significantly lower in patients with IPD compared to HC, particularly in middle-stage IPD.
• Reduced RD was most pronounced in the third REM sleep episode.
• In early-stage IPD, RD showed significant correlations with subjective sleepiness scores (PDSS and NMSQuest).

Conclusions:

• REM density is reduced in patients with idiopathic Parkinson disease.
• Reduced RD correlates with subjective reports of sleep impairment and may serve as a biomarker for excessive daytime sleepiness in IPD.
• This finding suggests potential involvement of brainstem REM-generating sites in IPD and highlights RD as a promising tool for sleep research in this population.