Microsleep episodes in the borderland between wakefulness and sleep

Area of Science:

• Neuroscience
• Sleep Medicine
• Electroencephalography (EEG) Analysis

Background:

• The transition zone between wakefulness and sleep, characterized by microsleep episodes (MSEs), is poorly defined by current sleep scoring guidelines.
• Existing American Academy of Sleep Medicine (AASM) criteria overlook MSEs, potentially impacting diagnostic accuracy and safety, particularly during tasks like driving.
• There is a need for refined criteria to objectively assess the wake-sleep transition and its associated phenomena.

Purpose of the Study:

• To develop and validate the Bern continuous and high-resolution wake-sleep (BERN) criteria for visual scoring of the wake-sleep transition zone.
• To specifically focus on identifying electroencephalography (EEG)-visible microsleep episodes (MSEs) that are often missed by conventional methods.
• To compare the utility of the BERN criteria against AASM guidelines in the context of the Maintenance of Wakefulness Test (MWT).

Main Methods:

• Retrospective scoring of Maintenance of Wakefulness Test (MWT) trials from 76 patients using both AASM and the newly developed BERN criteria.
• Comparison of visual scoring results with quantitative EEG spectral analysis to objectify MSE identification.
• Analysis of the relationship between MSE occurrence, sleep latency, and patient characteristics.

Main Results:

• The latency to the first microsleep episode (MSE) was significantly shorter than the sleep latency as defined by AASM criteria.
• A substantial number of MSEs were observed between the initial MSE and the onset of sleep, highlighting a critical transitional period.
• Series of MSEs were more prevalent in patients with shorter sleep latencies, while isolated MSEs were more common in those who did not achieve sleep.

Conclusions:

• The developed BERN criteria provide a valuable extension to the AASM guidelines for detailed analysis of the wake-sleep transition zone.
• The BERN criteria are particularly effective for in-depth assessment during the Maintenance of Wakefulness Test (MWT).
• Objective quantification via EEG spectral analysis supports the visual identification of MSEs, enhancing the reliability of the BERN criteria.