Intra‐individual stability of NREM sleep quantitative EEG measures in obstructive sleep apnea

Abstract

Electroencephalography is collected routinely during clinical polysomnography, but is often utilised to simply determine sleep time to calculate apnea–hypopnea indices. Quantitative analysis of these data (quantitative electroencephalogram) may provide trait‐like information to predict patient vulnerability to sleepiness. Measurements of trait‐like characteristics need to have high test–retest reliability. We aimed to investigate the intra‐individual stability of slow‐wave (delta power) and spindle frequency (sigma power) activity during non‐rapid eye movement sleep in patients with obstructive sleep apnea. We recorded sleep electroencephalograms during two overnight polysomnographic recordings in 61 patients with obstructive sleep apnea (median days between studies 47, inter‐quartile range 53). Electroencephalograms recorded at C3‐M2 derivation were quantitatively analysed using power spectral analysis following artefact removal. Relative delta (0.5–4.5 Hz) and sigma (12–15 Hz) power during non‐rapid eye movement sleep were calculated. Intra‐class correlation coefficients and Bland–Altman plots were used to assess agreement between nights. Intra‐class correlation coefficients demonstrated good‐to‐excellent agreement in the delta and sigma frequencies between nights (intra‐class correlation coefficients: 0.84, 0.89, respectively). Bland–Altman analysis of delta power showed a mean difference close to zero (−0.4, 95% limits of agreement −9.4, 8.7) and no heteroscedasticity with increasing power. Sigma power demonstrated heteroscedasticity, with reduced stability as sigma power increased. The mean difference of sigma power between nights was close to zero (0.1, 95% limits −1.6, 1.8). We have demonstrated the stability of slow‐wave and spindle frequency electroencephalograms during non‐rapid eye movement sleep within patients with obstructive sleep apnea. The electroencephalogram profile during non‐rapid eye movement sleep may be a useful biomarker for predicting vulnerability to daytime impairment in obstructive sleep apnea and responsiveness to treatment.

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

“…Numerous studies have reported a relationship between EEG power and daytime sleepiness. 10 , 27 , 28 This study also found a correlation between the ESS score and the average absolute power of delta and DAR ( P < 0.05). This confirmed that slow frequency EEG activity may be a clinical biomarker of daytime sleepiness.…”

Improvements in cognitive function and quantitative sleep electroencephalogram in obstructive sleep apnea after six months of continuous positive airway pressure treatment

“…We also acknowledge there is night-to-night variability in polysomnography measures of sleep that may have contributed to the differences observed before and after CPAP. However, our recent analysis of EEG profiles on patients with OSA recorded in the sleep laboratory on two different nights showed remarkable intra-individual stability in NREM delta and sigma power [ 44 ]. We used a standardised computerised battery of performance tasks assessing cognitive domains known to be impaired in OSA [ 25 ] with demonstrated sensitivity to CPAP treatment.…”

Sleep electroencephalography biomarkers of cognition in obstructive sleep apnea

“…While no sex differences were noted for SWA in OSA, differences were found predictably across age groups with younger OSA patients having significantly higher relative SWA compared with elderly OSA patients (Lee et al, 2016; Munoz‐Torres et al, 2020). SWA in OSA also remained stable across time within individuals during an average time period of 3 months with no clinical or OSA severity changes (Poon et al, 2019). However, SWA might be affected by changes in disease severity over longer periods of time.…”

“…Several studies have examined sleep spindles in the OSA population, as well as changes in spindle characteristics after OSA treatment. Spindles in NREM sleep were shown to be highly stable across nights in patients with OSA, at testing intervals ranging from 13 days up to 3 years (Poon et al, 2019). Early studies based on PSA and an automatic spindle detector showed that spindle density and spindle frequency were lower in middle‐aged patients with mild‐to‐moderate OSA compared with non‐OSA controls (Guilleminault et al, 2001; Himanen et al, 2003; Huupponen et al, 2003; Ondze et al, 2003).…”