Abstract
Sleep plays a critical role in maintaining overall health and well-being, impacting both psychological and physiological functions. However, sleep disorders such as insomnia, obstructive
sleep apnea (OSA), and narcolepsy are becoming increasingly prevalent, significantly affecting individual’s quality of life. Effective sleep stage classification is essential for diagnosing
and treating these disorders. Traditional methods like polysomnography (PSG) are the gold
standard for diagnosing sleep disorders, but they are expensive, cumbersome, and not easily
accessible due to the need for specialized equipment and trained personnel. Moreover, PSG
relies heavily on electroencephalogram (EEG) data, which, despite its effectiveness, presents
practical challenges in non-clinical settings due to the complexity of electrode placement and
patient discomfort. Innovative strategies in wearable technology using supervised deep learning
techniques offer a promising alternative for enhancing sleep stage classification, making it more
accessible and user-friendly.
This work aims to overcome these limitations by exploring the potential of using electrooculogram (EOG) signals for sleep stage classification. EOG signals, which are non-invasive and can
be more easily integrated into wearable technology, offer a promising alternative for long-term
sleep monitoring and provide a more comfortable experience for patients. The core contribution of this research is the design and implementation of a novel SE-ResNet-Transformer model.
This model architecture combines the strengths of Squeeze-and-Excitation Residual Networks
(SE-ResNet) and Transformer encoders, tailored to handle the unique characteristics of EOG
signals. The SE-ResNet component enhances feature extraction by adaptively recalibrating
feature responses, allowing the model to focus on the most informative aspects of the EOG
signal. The Transformer encoder component captures the temporal dependencies within the
EOG signals, enabling the model to understand the dynamic transitions between sleep stages.
The performance of the SE-ResNet-Transformer model was rigorously evaluated using three
publicly available datasets—SleepEDF-20, SleepEDF-78, and SHHS. The model demonstrated
superior accuracy and robustness across different datasets, with its EOG-based performance
comparable to models trained with EEG data. This suggests that EOG is a viable alternative
for sleep monitoring, particularly relevant for the development of wearable technology. Extensive ablation studies were conducted to fine-tune the model’s parameters and configurations,
providing valuable insights into optimal settings for window sizes and strides, and enhancing the model’s efficiency and performance. Techniques like 1D-Gradient-weighted Class Activation Mapping (Grad-CAM) and t-distributed Stochastic Neighbor Embedding (t-SNE) plots
were employed to visualize the model’s decision-making process, emphasizing transparency and
interpretability.
In addition, this work introduces the pioneering Indian SLEEP dataset of ischemic Stroke patients (iSLEEPS) which addresses a gap in the availability of India-specific sleep disorder data,
with a particular focus on the impact of ischemic stroke on sleep health. This dataset is comprehensive, including detailed clinical annotations that cover patient demographics, diagnoses,
and sleep stages. Cutting-edge deep learning models, including CNN-based, LSTM-based, and
Transformer-based architectures, were trained on raw single-channel EEG and EOG signals.
Among these, the Transformer-based model showed remarkable performance in sleep stage
classificatzions using single-channel EOG data. The successful validation of these models on
the iSLEEPS highlights their potential to enhance diagnostic tools and therapeutic strategies,
thereby contributing to improved patient outcomes and fostering global collaboration in sleep
research.
In conclusion, this thesis presents advancements in the field of automated sleep stage classification using wearable technology and supervised deep learning. By leveraging EOG signals
and deep learning architectures, this research offers promising solutions for more accessible, accurate, and comfortable sleep monitoring, ultimately aiming to bridge the gap between clinicalgrade sleep monitoring and everyday health management tools, thus enhancing sleep health
and overall wellness