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：多导睡眠图（PSG）当前是评估睡眠障碍的黄金标准。因其带来的不适感、不适用于家庭使用以及在睡眠质量评估中引入偏差等问题，有必要探索更具微创性、经济高效且便携的替代方案。耳内脑电（in-ear-EEG）传感器是极具前景的候选方案之一，具有舒适度高、电极位置固定、抗电磁干扰能力强及用户友好等优势。本研究旨在建立一种评估耳内脑电信号与标准PSG信号相似性的方法。方法：我们评估了由PSG与耳内脑电推导出的睡眠分期图之间的一致性。从PSG和耳内脑电的30秒时程片段中提取时域和频域特征，仅考虑PSG评估者与耳内脑电评估者分期一致的片段。引入一种量化PSG导联与单通道耳内脑电信号相似性的方法：通过基于Jensen-Shannon散度的特征相似性指数（JSD-FSI），对PSG与耳内脑电信号中按睡眠阶段和受试者分别提取的选定特征分布进行比较。结果：我们发现评估者间存在较高变异性，主要源于评估者在分析耳内脑电信号时的不确定性。结果表明，PSG与耳内脑电信号具有高度相似性（JSD-FSI：清醒期0.61±0.06，非快速眼动期0.60±0.07，快速眼动期0.51±0.08），该相似性值与基于标准PSG导联组合独立计算的数值一致。结论：耳内脑电是家庭睡眠监测的有效解决方案，但需在更大规模、更具异质性的数据集中开展进一步研究。