Dynamic changes in electroencephalogram spectral power with varying apnea duration in older adults

Abstract

Sleep apnea elicits brain and physiological changes and its duration varies across the night. This study investigates the changes in the relative powers in electroencephalogram (EEG) frequency bands before and at apnea termination and as a function of apnea duration. The analysis was performed on 30 sleep records (375 apnea events) of older adults diagnosed with sleep apnea. Power spectral analysis centered on two 10‐s EEG epochs, before apnea termination (BAT) and after apnea termination (AAT), for each apnea event. The relative power changes in EEG frequency bands were compared with changes in apnea duration, defined as Short (between 10 and 20 s), Moderate (between 20 and 30 s) and Long (between 30 and 40 s). A significant reduction in EEG relative powers for lower frequency bands of alpha and sigma were observed for the Long compared to the Moderate and Short apnea duration groups at BAT, and reduction in relative theta, alpha and sigma powers for the Long compared to the Moderate and Short groups at AAT. The proportion of apnea events showed a significantly decreased trend with increased apnea duration for non‐rapid eye movement sleep but not rapid eye movement sleep. The proportion of central apnea events decreased with increased apnea duration, but not obstructive episodes. The findings suggest EEG arousal occurred both before and at apnea termination and these transient arousals were associated with a reduction in relative EEG powers of the low‐frequency bands: theta, alpha and sigma. The clinical implication is that these transient EEG arousals, without awakenings, are protective of sleep. Further studies with large datasets and different age groups are recommended.

Electroencephalographic Activity and Cognitive Function in Middle-Aged Patients with Obstructive Sleep Apnea Before and After Continuous Positive Airway Pressure Treatment

“…However, the EEG signals routinely collected by PSG have not been fully utilized. There have been a number of studies that have analyzed the EEG power of OSA, 17 , 18 but the results of the studies were not consistent. One of the reasons is that there was no unified standard for the sampling method of EEG signals or the definition of the frequency spectrum.…”

Gamma Power of Electroencephalogram Arousal Is Modulated by Respiratory Event Type and Severity in Obstructive Sleep Apnea

“…This result is in opposition to the findings of Dingli et al [13], who observed an increase in relative post-event delta power during NREM sleep; however, this increase was observed only when there was no visible EEG arousal at event termination. Relative theta (4-8 Hz) power has also been observed both to decrease [13], [14] and increase [12] after apnea and hypopnea termination. Relative alpha (8)(9)(10)(11)(12) and sigma (12)(13)(14)(15)(16) powers are known to increase after apnea and hypopnea termination in Stage R sleep [12], [14].…”

“…Relative theta (4-8 Hz) power has also been observed both to decrease [13], [14] and increase [12] after apnea and hypopnea termination. Relative alpha (8)(9)(10)(11)(12) and sigma (12)(13)(14)(15)(16) powers are known to increase after apnea and hypopnea termination in Stage R sleep [12], [14]. This increase has also been observed in NREM sleep when respiratory events were terminated by arousals [13].…”

“…Even though the investigated populations have been small (n = 13 [12], n = 15 [13], and n = 30 [14]), it is evident that the EEG spectral content is different before and after respiratory event termination. However, the amount of research comparing the post-event EEG spectral content between different respiratory events is limited.…”

“…The majority, approximately 64-97%, of respiratory event terminations are associated with visible EEG arousals [8]- [11]. Various studies have investigated the shift in the EEG frequency before and after respiratory event terminations [12]- [14]. However, some discrepancies remain in the findings between these studies.…”