Threshold Values of Sleep Spindles Features in Healthy Adults Using Scalp-EEG and Associations With Sleep Parameters

Area of Science:

• Neuroscience
• Sleep Science

Background:

• Sleep spindles are key electrophysiological markers of brain activity during sleep.
• Spindle characteristics (duration, frequency, amplitude, density) vary with age and sex and are altered in neurological/psychiatric conditions.

Purpose of the Study:

• To establish the first normative threshold values for sleep spindle characteristics in healthy adults.
• To explore associations between sleep spindle parameters and other sleep metrics.

Main Methods:

• An observational prospective study involving 80 healthy adults (aged 19-74, 50% female).
• In-laboratory polysomnography was used to record sleep.
• Sleep spindles during N2 sleep were analyzed using automated procedures, categorized as fast (>13 Hz) or slow (≤13 Hz).

Main Results:

• Threshold values for fast spindles: duration (0.80-1.11s), frequency (13.4-14.3 Hz), amplitude (5.2-15.2 μV), density (1.0-5.8/min).
• Threshold values for slow spindles: duration (0.79-1.17s), frequency (12.3-12.9 Hz), amplitude (4.1-13.2 μV), density (0.03-3.15/min).
• Spindle density, amplitude, and duration decreased after age 40. Females had higher spindle amplitudes. Fast spindle amplitude correlated with excessive daytime sleepiness and increased slow-wave sleep.

Conclusions:

• This study provides the first normative threshold values for sleep spindle characteristics in healthy adults.
• These established thresholds are vital for developing novel biomarkers for neurological and psychiatric disorders.
• The findings enhance our understanding of the sleeping brain's complex functions.