Sleep Tracking Technology: A Technical Path to Sweet Dreams
Consumers sporting Apple Watches and Fitbits most likely did not make their purchases with the sole intent of monitoring their sleep. However, with this added feature included in wearable devices and users' enthusiastic responses, sleep tracking technology is becoming a sought-after gem. Before jumping on the bandwagon, let us dive deeper into the technology and explore what it is about and where it is headed.
How does Sleep Technology work?
Sleep monitoring was introduced to wearable technologies. These devices collect motion-based features from an accelerometer sensor to determine whether the user was awake or asleep. This method is based on actigraphy, which relies on the accelerometer to measure motion patterns, connecting motion to being awake and lacking the motion to be asleep. An obvious flaw in the algorithm is that a consumer could lie awake in bed for hours, and the device would misinterpret this as sleep. While this information can still be used and analyzed, it is not the most accurate. There have been many advances in sensor technology that have attempted to increase the accuracy of the measurements required to monitor a user's sleep.
Today, wearable technologies can record a wide range of bio-signals, including skin temperature and photoplethysmography (PPG). These additions to the previous actigraphy approach dive deeper into our sleep patterns and measure sleep stages (light, deep, REM). It marks a significant enhancement to the first wearable technologies that only measured wake and sleep. PPG can give accurate estimations of heart-rate variability, serving as an indicator of cardiac autonomic function during sleep. Companies are introducing improved sleep monitoring algorithms every year as the feature expands in popularity. The low-cost, cloud-based integration and ease of use contributed to tech giants dipping their foot (or diving headfirst) into sleep monitoring technology.
Wearable technologies are increasing in size and demand, and many companies are taking advantage of it. Some companies that include sleep tracking technology on their wearable devices are:
The only company above that is dedicated to sleep monitoring is Beddit. Apple acquired Beddit in 2017, so sleep tracking technology is likely sought after as a part of a comprehensive health assessment product. While other types of devices track sleep, the smartwatch remains the most popular; Apple and Fitbit are huge players in this field.
The Apple Watch has been dominating the smartwatch industry, with nearly 31 million units shipped in 2019. "Apple shipped 7.6 million smartwatches worldwide in the first quarter of 2020, according to recent data from Strategy Analytics, an increase of 23% compared to 6.2 million in the first quarter of 2019." The data show that wearable technology is here to stay even during a global pandemic and grow regardless of economic conditions.
Apple acquiring Beddit led many to speculate that Apple would soon add sleep tracking technology to the Apple Watch. On June 22, 2020, sleep tracking technology was added to the Apple Watch with watchOS 7.
In the watchOS 7 press release, Apple touts the watch's "detection of micro-movements from the watch's accelerometer, which signals respiration during sleep, Apple Watch intelligently captures when the wearer is sleeping and how much sleep they get each night." The Apple Watch also uses motion sensors, heartbeat sensors, and microphones to track the user's sleep. They offer user-friendly and visually pleasing representations of the data collected overnight. Other sleep-related features on the Apple Watch include setting bedtimes and wake-up times, a Sleep Mode that darkens the screens and turns on Do Not Disturb, and weekly sleep trend charts.
Apple Watch – Sleep Mode (Source)
Fitbit was introduced in 2009 as a clip-on device that measured a user's steps and sleep. As Fitbit expanded, the company focused heavily on its watch, which also includes sleep tracking technology. Fitbit's sleep tracking also includes heart rate sensors and motion detectors to track sleep.
The benefits of sleep tracking, according to Fitbit, are being able to:
See how well you sleep
Wake with calm (silent alarm)
Get insights about your night
Create better habits for better rest
Fitbit Sleep Chart (Source)
Both devices, and most others on the market, offer similar results regarding advancements and accuracy of sleep tracking. However, with the exciting reveal of Apple adding sleep tracking to its watch, along with the growth projected for the watch, we may see more attention to advancements in sleep algorithms soon.
Accuracy and Relevance of Results
Polysomnography (PSG) is believed to be the "gold standard" for sleep analysis. It "records your brain waves, the oxygen level in your blood, heart rate and breathing, as well as eye and leg movements."
Polysomnography(PSG) Setup (Source)
However, PSG is intrusive and requires expensive resources. However, accurate results from wearable sleep trackers could prevent users from making incorrect assumptions about their sleep and help researchers/medical professionals evaluate sleep more effectively and at a lower cost.
A study compared the data from both wearable wrist activity tracker (Fitbit) and polysomnography (and standard actigraphy). 24 healthy adults wore a Fitbit and actigraph during an overnight PSG. The results showed that the Fitbit has limitations similar to the actigraphy, such as over-approximating sleep quality and total sleep time. This outcome highlights that the information obtained from an over-the-counter wearable sleep tracker may be useful for healthy users. Still, those with sleep issues/disorders may need more accurate results by a healthcare provider.
Cathy Goldstein, M.D., a physician who specializes in sleep, stated that sleep data's relevance over long periods of healthy individuals is questionable. She also pointed out that it is possible for users to become obsessed with getting the perfect amount of sleep, as indicated by their sleep trackers, a condition known as Orthosomnia. With that said, Goldstein explains that the primary purpose of sleep trackers today is to observe sleep trends and pay attention to common sleep disrupters, such as caffeine and alcohol.
Sleep Tracking Technology and IP
As sleep tracking technology advances and expands, naturally, companies are securing related patents. IPWatchDog names the top five U.S. patent assignees for fitness wearables:
Fitness Wearables Patent Analysis (Source)
In addition to acquiring Beddit, Apple has recently patented technology to create bedding with sleep tracking technology. In 2017, Google received a patent that uses an infrared sensor to monitor a consumer's sleep, and in 2019, Google purchased the Fossil Group's intellectual property relating to wearables for $40 million. Tech giants like Apple and Google are looking to keep a competitive edge in the wearable technology sector and seek protection for their intellectual property.
The figure below shows the number of patents filed each year from 2000-2018.
Increase in wearables patent activity over time (Source)
Around 2015, there was a massive increase in patent applications relating to wearable technology. This phenomenon can be correlated to the increase in Internet of Things (IoT) devices, which can send and receive data via a wireless network. With the growth of wearable technology patents, we can expect that we continue to see an increase in sleep technology patents.
The Near and Far for Sleep Tracking
There is no doubt that sleep tracking technology is in high demand as the wearable technology field expands. The technology is intriguing, with sensors that can monitor heart rate, temperature, and motion to detect whether a user is awake or asleep. Tech giants are continuing to innovate in the field and release new versions of sleep algorithms each year.
With that said, the accuracy and relevance of these devices' results to an average healthy consumer have come into question. Currently, sleep tracking technology is useful for monitoring sleep variations when consuming certain substances and setting sleep goals, and monitoring progress against them. Medical professionals have noted that some users can become obsessed with the data their wearable device shows them, causing anxiety and negatively impacting the user's sleep. Also, the sleep data obtained from these devices should only seek further medical advice when a user feels that a sleep issue is occurring.
However, with wearable technology patents and IP increasing each year, sleep tracking algorithms are continually improving. There is no telling how accurate and useful they may become in the future. Still, the technology is exciting for users and medical professionals due to the low cost and ease of use of the devices.
Associate Consultant at Lumenci
Ryan is a Software and Web/App Development Expert at Lumenci. Ryan holds a Bachelor of Science in Computer Science from the University of Texas at Austin.