Study Objectives: Polysomnography (PSG) currently serves as the benchmark for evaluating sleep disorders. Its discomfort, impracticality for home-use, and introduction of bias in sleep quality assessment necessitate the exploration of less invasive, cost-effective, and portable alternatives. One promising contender is the in-ear-EEG sensor, which offers advantages in terms of comfort, fixed electrode positions, resistance to electromagnetic interference, and user-friendliness. This study aims to establish a methodology to assess the similarity between the in-ear-EEG signal and standard PSG. Methods: We assess the agreement between the PSG and in-ear-EEG derived hypnograms. We extract features in the time- and frequency- domain from PSG and in-ear-EEG 30-second epochs. We only consider the epochs where the PSG-scorers and the in-ear-EEG-scorers were in agreement. We introduce a methodology to quantify the similarity between PSG derivations and the single-channel in-ear-EEG. The approach relies on a comparison of distributions of selected features -- extracted for each sleep stage and subject on both PSG and the in-ear-EEG signals -- via a Jensen-Shannon Divergence Feature-based Similarity Index (JSD-FSI). Results: We found a high intra-scorer variability, mainly due to the uncertainty the scorers had in evaluating the in-ear-EEG signals. We show that the similarity between PSG and in-ear-EEG signals is high (JSD-FSI: 0.61 +/- 0.06 in awake, 0.60 +/- 0.07 in NREM and 0.51 +/- 0.08 in REM), and in line with the similarity values computed independently on standard PSG-channel-combinations. Conclusions: In-ear-EEG is a valuable solution for home-based sleep monitoring, however further studies with a larger and more heterogeneous dataset are needed.

翻译：研究目的：多导睡眠监测（PSG）目前是评估睡眠障碍的黄金标准。但其使用带来的不适感、居家应用的局限性以及对睡眠质量评估产生的偏差，促使人们探索创伤更小、成本更低、更便于携带的替代方案。耳内脑电图（in-ear-EEG）传感器是一个有前景的候选方案，其优势在于舒适性、电极位置固定、抗电磁干扰能力强以及用户友好性。本研究旨在建立一种评估耳内脑电图信号与标准PSG相似性的方法。方法：我们评估了基于PSG与耳内脑电图推导的睡眠分期图之间的一致性。我们从PSG和耳内脑电图的30秒时间段中提取时域和频域特征，仅考虑PSG评分者与耳内脑电图评分者达成一致的时段。我们引入了一种方法，用于量化PSG导联与单通道耳内脑电图之间的相似性。该方法通过基于Jensen-Shannon散度的特征相似性指数（JSD-FSI），比较从PSG和耳内脑电图信号中、针对每个睡眠阶段和每名受试者所提取的选定特征集合的分布。结果：我们发现评分者内部存在较高变异性，这主要源于评分者在评估耳内脑电图信号时的不确定性。研究表明，PSG与耳内脑电图信号的相似性较高（JSD-FSI：清醒阶段0.61 ± 0.06，NREM阶段0.60 ± 0.07，REM阶段0.51 ± 0.08），且与基于标准PSG通道组合独立计算的相似性值相符。结论：耳内脑电图是居家睡眠监测的一种有价值方案，但仍需基于更大规模、更具异质性的数据集开展进一步研究。