Pioneering Sleep Analysis: A Precedent Study on Forecasting Breathing Events Using Smartwatch Sensor Data

The Evolving Future of Sleep Monitoring and Health Assessment

Nocturnal breathing, while integral to our health, has often been relegated to the background in medical discussions. Variations in breathing patterns during sleep might hint at underlying health issues, remaining elusive without appropriate monitoring. Smartwatches, with their advanced sensor technology, show promising potential in detecting, recording, and analyzing these breathing events, potentially revolutionizing insights into sleep health. At the heart of this potential breakthrough is the ability of these devices to continuously monitor physiological signals like heart rate, blood oxygen saturation, and movement throughout the night. By leveraging this data, emerging algorithms may soon be able to predict and identify anomalies in breathing patterns, suggesting a burgeoning early warning system.

Over the past decade, wearable health technology has made significant strides, particularly in sleep monitoring. Despite these advancements, accurately predicting nocturnal breathing events has remained a challenge. This challenge has catalyzed the integration of superior smartwatch hardware with pioneering software algorithms, hinting at a potential real-time solution. The pathfinding efforts in this realm are credited to the dedicated Research and Development team at the Samsung R&D Institute Ukraine (SRUKR). Their potentially transformative work secured a spotlight at the 45th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBC 2023[1]

Picture 1   A local indigenous individual welcomes conference participants [2]

EMBC 2023 was hosted with grandeur in Sydney. Drawing 2,455 attendees from over 50 countries, the event celebrated a rich tradition that began in 1960. The vast majority of participants were international, highlighting the global influence of the society, with a significant proportion being students. Distinguished speakers, such as Peter Hunter and Nimmi Ramanujam, led enriching sessions that covered diverse themes from Biomedical Signal Processing to Therapeutic and diagnostic Systems. The conference provided an excellent platform for networking, fostering collaborations, and discussing groundbreaking advancements in biomedical engineering.

Picture 2   EMBC 2023 opening ceremony at the Sydney International Convention Centre [2]

From Traditional Methods to New Horizons: The Precedent Exploration of Sleep Analysis

Historically, polysomnography (PSG) has held the gold standard title in sleep analysis. However, its intrinsic limitations, from the inconvenience of tethered overnight hospital stays to the substantial expenses incurred, have generated a growing appetite for alternative methods that are both more accessible and cost-effective.

The realm of wearable devices emerges as a promising avenue in this context. These devices, once mere extensions of personal style or basic fitness monitors, are now at the forefront of health technology, hinting at the future of sleep monitoring. The metamorphosis from rudimentary wearables to sophisticated smartwatches signals a pivotal shift in the landscape. Contemporary smartwatches, equipped with accelerometers and photoplethysmography (PPG) sensors, are showing the capability to consistently monitor pivotal physiological markers. As they accumulate and catalogue extensive data throughout the night, we glimpse the potential for a transformative leap in sleep health understanding.

Picture 3   Overview of the existing polysomnography (PSG) setup (left) and recently developed wearable devices (right) for sleep monitoring [3]

Each movement, heartbeat, and subtle change in breathing rhythm during sleep paints a picture of an individual's nighttime activities. Among these, breathing events, especially abnormalities, capture keen attention due to their potential health implications. For instance, sleep apnea, which disrupts regular breathing patterns, might lead to lowered oxygen levels in the bloodstream. Similarly, hypopnea's shallow breaths or decreased respiratory amplitude pose their own concerns. And, while many view snoring as innocuous, it sometimes signifies deeper respiratory issues.

Picture 4   Breathing events during nocturnal sleep [4]

In this context, the SRUKR Health Innovations team initiated a precedent study to decipher these voluminous sleep data. Their methodology? Harnessing advanced algorithms to sift through and interpret these data, converting nocturnal readings into potentially actionable insights regarding sleep health. Their method, at this juncture, combines the strengths of recurrent neural networks and deep learning, fine-tuned to discern even subtle breathing anomalies. With diligent training and iterative fine-tuning, the algorithms show the possibility to identify and even predict respiratory events (RE), though there's a journey ahead for perfection.

Given the challenges faced, SRUKR Health Innovations delved into the realm of respiratory disorders during nocturnal sleep, conditions that alarmingly afflict between 5% and 10% of the global population. Traditional diagnostic methods like polysomnography (PSG), although deemed the "gold standard," come with their fair share of limitations – they're expensive, cumbersome, and not designed for in-home diagnostics. The team, therefore, pivoted towards the potential of consumer smartwatches, devices that have seamlessly integrated into the lives of many.

Picture 5   Samsung Galaxy Watch biosensors [5]

Harnessing these wearables' accelerometers and photoplethysmography sensors, the researchers focused on a unique encoder-decoder recurrent neural network (NN) for forecasting respiratory patterns. The team, in its nascent stages, developed a model capable of parsing raw data, filtering anomalies, and distilling vital signals from sensor outputs. This processed data is subsequently navigated through a complex neural system enriched with convolutional neural networks (CNN) and long short-term memory cells (LSTM) to anticipate respiratory events.

Picture 6   General System flowchart: Galaxy Watch sensors data - NN model – forecasted RE pattern.

Insights from the team's initial experiments elucidate their journey's challenges and successes. As the team sought to predict respiratory events over extended periods, there was an observable decline in the precision of the predictions. However, the effectiveness of the developments from SRUKR Health Innovations part remained fairly steady regardless of the amount of initial history data used, underscoring the potential robustness of their model.

Picture 7   Detailed scheme of the system: signal pre-processing block (upper figure) and encoder-decoder NN architecture (lower figure). Galaxy Watches’ sensors: ACC – 3-axis accelerometer; PPG – plethysmography; IBI – inter-beat-intervals extracted from PPG sensor.

Furthermore, the team delved into two more insightful areas. Firstly, they aimed to determine if any respiratory event could occur within a predicted timeframe. Secondly, they estimated how many such events might occur. In layman's terms, while the first analysis gauged the chances of such an event happening, the second tried to quantify how often. The outcomes of these studies, in simpler words, suggest that their predictions are mostly on point, but there are times when it could either underestimate or overestimate the actual events based on how far into the future they're predicting.

To summarize, SRUKR Health Innovations' initial steps in sleep health research have laid a promising foundation, recently spotlighted at the EMBC 2023 conference. Their novel endeavors offer a glimpse into a future where everyday wearables might evolve into valuable diagnostic aids for sleep-associated respiratory ailments. With sights set on refining their approach, the team aspires to eventually pinpoint specific respiratory event types and their commencement. Their preliminary work not only exemplifies their commitment but also heralds a potential paradigm shift in sleep medicine's landscape.

Picture 8   SRUKR engineer Anastasiia Smielova at the EMBC 2023




[3] Kwon S, Kim H, Yeo WH. Recent advances in wearable sensors and portable electronics for sleep monitoring. iScience. 2021 Apr 21; 24(5):102461. doi: 10.1016/j.isci.2021.102461.