The sleep technology space has exploded, with hundreds of products promising better sleep through wearables, apps, smart bedroom accessories, and innovative travel devices.
There is certainly no shortage of demand for this technology. According to the CDC, 35% of adults get fewer than 7 hours of sleep per night. Fortune Magazine reported lack of sleep costs an estimated $411 billion in lost wages, and accounts for nearly 1.2 million missed working days per year.
The fact that more than a third of the adult population is sleep deprived becomes particularly alarming when considering the importance of sleep for health and cognition. Not only is sleep crucial for metabolism, immune function, and organ health, but it also plays a major role in cognition, memory, sensory-motor function, and emotion regulation.
The industry certainly recognizes the potential for the sleep tech market: Investors were estimated to have funneled $2 billion into wellbeing startups as of last month (according to Kaleido Insights). In 2018, the sleep tech market in particular was expected to be valued at nearly $80 billion by 2022.
But do these products work? Or is their promise of sleep, to quote sleep pioneer William Dement, just a promise?
Apps
Perhaps the most plentiful and inexpensive tech in this space are sleep-tracking apps. Sleep Cycle, Sleep as Android, and similar apps use sound or movement to determine the user’s level of sleep, categorizing these as Awake, Light Sleep, and Deep Sleep.
These apps then provide a breakdown of the user’s sleep patterns using an algorithm that generates statistics based on the activity counts for the night. Features vary from app to app, but users typically have access to their sleep duration, sleep efficiency, and a graph depicting time spent in each stage of sleep across the night.
In some cases, the user can access an estimation of their “sleep debt,” or how much sleep loss they’re accumulating over several days.
In addition to providing users insight into their own sleeping habits, these apps typically provide a smart alarm feature, which wakes the user in his or her lightest stage of sleep. The idea is to reduce sleep inertia, or the grogginess we experience immediately upon waking.
Apps that use the microphone feature also record snoring and sleep talking, which could be useful for the consumer when determining whether to seek treatment for sleep apnea or other sleep disorder.
Beyond sleep tracking are apps that look to improve the user’s sleep more directly, for instance by providing calming sounds and meditations to promote sleepiness. Calm, an app that offers meditations and stories for better sleep, recently raised $88 million, bringing their funding to $116 million, according to Kaleido Insights.
The idea is to provide recordings of stories told in soothing voices to promote relaxation and theoretically lull users into a deep sleep. As their website states, “We loved having bedtime stories read to us as children so why should that stop now that we’re all grown up?”
Wearables
For those willing to invest a little more in sleep tech are wearable devices. Typically worn on the wrist, these gadgets use accelerometry (read: motion-detectors) to determine which level of sleep the user is in.
In this market, Fitbit is king, with a line of wearables for nearly every age and budget. The mid-range Charge 3 was released in October 2018, and rumors are already circulating about the features to be included in the Charge 4.
Like apps, wearables like Fitbit provide insight into sleep patterns and makes personalized recommendations based on the user’s goals and habits.
However, one of the reasons Fitbit is ahead of the game is because it uses heart rate to track sleep, which theoretically could make it more accurate than the competition.
The company is also beta testing Sleep Score, a new feature that uses pulse oximetry to provide the user reports about their breathing quality during sleep, a useful feature for those who suspect air quality issues or sleep apnea may be ruining their slumber.
Garmin is a close second in the fitness tracker market, but many agree their sleep features still lag behind that of Fitbit’s. The Vivosmart 4, their highest rated product according to techradar.com, offers similar features as Fitbit Charge at comparable accuracy.
Of course, Apple is in on the sleep tech race, too. In addition to providing a sleep tracker on the Apple Watch, the company recently purchased Beddit, a
Finland-based startup specializing in sleep tracking devices and apps. It is unknown what new features will be included with the Apple Watch Series 5; however, its release, set for later this year, is rumored to be delayed to 2020 in order to incorporate new sleep-related functionalities.
One issue with using the Apple Watch, and other wrist-worn devices, to track sleep is that it requires users wear the device all the time, which can be uncomfortable.
Apple may have a solution: Monitor your sleep via sensors in your bed. According to a recent patent, Apple plans to noninvasively monitor users’ sleep via sensors placed under mattress or pillow, reducing the need to wear a physical device to bed.
Another solution is to go smaller. Oura provides the same functions as a wrist-worn wearable, but in a comfortable ring. Another key feature of the Oura ring is that it measures body temperature, a feature that is hard to find in wrist-worn sleep trackers.
Of course, body temperature isn’t necessary for sleep tracking, but it is another data point in the user’s repertoire to help them get better sleep. For instance, as one blogger pointed out, monitoring to their body temperature via the Oura ring demonstrated that choosing a lighter blanket resulted in a 17% increase in time spent in REM sleep.
These days, we need all the help we can get.
But how accurate are they?
The gold standard of sleep recording involves measuring brain waves, eye movements, and muscle tone in order to determine which stage of sleep the person is in.
All three of these metrics are necessary to stage sleep, which requires looking at each 30-second window of the entire sleep period and applying rules put in place by the American Association of Sleep Professionals. These rules help the sleep stager determine whether the sleeper is in stage 1 (NREM 1; sleep onset), stage 2 (NREM 2; light sleep), stage 3 (NREM 3, also known as slow-wave sleep; the deepest stage of sleep), or REM (rapid-eye movement sleep; dreaming sleep).
Apps and wearables in large part do not have access to these metrics, so they can’t detect the subtle brain changes needed to stage sleep in this way.
Instead, they rely on course-grained analysis based on movement and/or ambient sound in the environment. This is not entirely unlike Actigraphy, wrist-worn motion-sensitive devices used as a “quick-and-dirty” research method for sleep. The difference is that Actigraphs, and research-grade devices like them, are very well validated in the scientific literature.
A study from 2018 showed consumer devices are fairly accurate when compared to user-reported sleep. But, it should be noted that people are notoriously bad at correctly estimating their own sleep. Furthermore, self-reported sleep is actually more closely related to mood than it is to objective measures of sleep.
It is impossible to know how accurate these devices are since the algorithms used by these companies are carefully protected trade secrets. This is not just an issue for researchers: Consumers are clamoring for more accurate health insights as well. In June of last year, Fitbit was sued for inaccuracies in their heart rate readings, and a similar lawsuit regarding their sleep tracker was settled earlier this year.
Until we know what these devices are measuring, we can’t rule out that they are actually measuring variables indirectly related to sleep, such as mood. This may feel like an accurate sleep report to the user, because it correlates with their own subjective experience, but it may not actually be a reliable marker of objective sleep that is useful for changing sleep habits.
Beyond measuring sleep
There are a few devices on the market that can and do record brain waves for more accurate measurement — and direct manipulation — of sleep variables.
Notable of these is the Dreem 2, released last month, which delivers brief, precisely-timed sounds in phase with brain waves during deepest stage of sleep. The idea is to entrain brain rhythms to the sounds and boost their activity, a method that has been associated with improved memory consolidation.
I should mention I’m extremely familiar with this methodology, as I did a postdoctoral fellowship at the University of New Mexico in collaboration with Hughes Research Labs using a similar algorithm with electrical stimulation. Our work showed improvements in self-reported sleep quality, in addition to particular forms of memory.
It is much easier and less invasive to use sound, as the Dreem 2 does, than electrical stimulation as we did. Although, at the moment this author is unsure of any studies specifically showing sound improves sleep quality (but please do point me to any developments in the comments).
Nonetheless, I am very excited to try the Dreem 2.
Also on my wish list is the iWinks Aurora. In addition to tracking sleep and offering a smart alarm feature, the Aurora headband uses EEG and eye movements to determine when the user is in REM sleep and emits light and sound stimulation to promote lucid dreaming.
Another company to watch is UrgoNight. Nominated for the CES 2019 Wearable Technology Innovation Award, this neurofeedback device has been all over the news lately.
The company asserts that using the device 20 minutes a day, 3 days per week is enough to make its users get to sleep 40% faster and have 53% fewer awakenings across the night.
One downside is that it doesn’t track sleep patterns; however, the obvious upside to that is that you don’t have to wear it while you sleep.
The company is currently taking pre-orders.
In summary, apps and wearables are great for tracking sleep if you don’t need clinical accuracy. These technologies provide insight into sleep patterns, which the user can then use to make informed decisions about his or her sleep habits.
A new wave of technology incorporates EEG into headbands to wear at night, offering a more accurate alternative. These devices have the added benefit of using light and sound to hack your sleep and dream space.
Perhaps 100% accuracy is not needed for these apps and wearables to improve your sleep. A lot of us are happy just to snuggle up with our tech as long as it’s helping us get a good night’s rest.