Everything you need to know about sleep tracking, including a round-up of the top wearable and bedside sleep tracking devices in 2018
- Why track sleep?
- Sleep tracking and the ‘quantified self’
- The rise of sleep tracking
- Heart rate
- EEG (electroencephalogram -brain activity)
- Sleep tracking apps
- Sleep tracking wearables
- Non-wearable sleep tracking options
- Contactless sleep tracking
- Our Top Recommended Sleep Trackers In 2018
- Polysomnography vs consumer sleep tracking
- How accurate are personal sleep trackers? (updated Nov 2018)
- Sleep tracking and your data
Do you struggle to get yourself out of bed in the morning? And when you reach work, do you wonder why everyone seems more energetic than you?
Perhaps you’ve wondered if you’re getting a full eight hours sleep every night? Or maybe you’re concerned you might have a sleep disorder?
One way to find out more is with sleep tracking.
Consumer sleep trackers come in many shapes and sizes including smartphone apps, wearables and bedroom-based sleep monitors. Whilst the technology is getting more sophisticated every year, most consumer sleep trackers are not yet regarded by medical professionals as accurate enough to identify specific sleep disorders.
For these type of medical insights you would need to undertake an overnight study, known as a polysomnogram in a sleep lab, considered the ‘gold standard’ for measuring sleep.
In this article we takes an in-depth look at why you might want to track your sleep, the different types of sleep trackers, and our recommendations for the best consumer sleep wearables and apps in 2018.
We’ll also take a look at the history of sleep tracking, and compare the differences between consumer sleep tracking, and what goes on in a sleep lab.
Why track sleep?
At its most basic, sleep tracking is a way to find out if you’re getting enough sleep and to measure the quality of your sleep.
A recent report by the CDC called America’s sleep problems a public health epidemic. The report highlighted a growing concern over sleep-related issues such as: the billions lost in economic productivity, fatal accidents caused by sleep deprivation, possible links with the obesity crisis, the rise in sleep apnea.
Sleep trackers can yield a lot of answers to questions such as:
- how many hours do I sleep each night?
- how long does it take for me to fall asleep?
- do I sleep peacefully or am I a restless sleeper?
- how much deep sleep, light sleep or REM do I get?
This information is compelling on its own, but if you’re serious about improving your health and well-being it can be potentially invaluable.
Because whilst on its own sleep tracker data is rarely enough to base a medical diagnosis on, it might give you enough insights into whether you might be suffering from a sleep disorder like sleep apnea.
Despite the sum of human knowledge, sleep largely remains a mystery. Increasingly however, science is starting to build a case that sleep, along with proper nutrition and exercise is one of the three pillars of health.
Sleep tracking and the ‘quantified self’
The quest for self-knowledge is not exactly a new trend. Two thousand years years ago the maxim ‘Know Thyself‘ was carved into the Temple of Apollo in ancient Greece. A few years ago the same sage advice made its way into the first Matrix movie.
The 21st century, however has a new spin on self-knowledge. In 2007, the quantified self (QS) movement was founded by two editors of the technology magazine Wired.
QS is a community of early adopters seeking to achieve self-knowledge through self-tracking technology including wearables, sensors and bio-monitors. Now a global movement embodying research, meetings and online communities, the QS movement was the first expression of interest into what personal sleep tracking technology could reveal about individual’s health and well-being.
10 years after the QS movement was founded, millions of people use gadgets and wearables to monitor all aspects of their daily lives, including exercise, diet, heart-rate, location, alertness, mood, productivity and of course, sleep.
The rise of sleep tracking
Apart from the QS movement, other trends have paved the way for the increased interest in sleep tracking in recent years.
First and foremost is the growing public awareness of the importance of sleep health. This has been fuelled by a tsunami of new research findings from sleep science in the past 20 years.
Then we also have high profile advocates like Arianna Huffington and bestselling author Dr Matthew Walker who have pushed sleep health back into the spotlight.
Another layer are the series of technological revolutions which have occured in the past 10 years including:
- the iPhone and smartphone revolution
- the rise of ‘big data’
- the trend towards personalised healthcare
- the emerging sleep technology industry
Fuelled by all these factors, more and more consumers are turning to smartphone apps, wearables and bedside sleep monitors to collect and analyse data about their sleep.
But how exactly does sleep tracking work? What can you learn from measuring your sleep? And how does consumer sleep tracking differ from lab-based sleep monitoring?
How do sleep trackers work?
Advances in microelectronics and software designed have spawned a plethora of sleep tracking gadgets. Sophisticated components are now commonplace in phones, and can be tailored to monitor a range of inputs such as physical activity, direction, location, sound, skin conductivity, heart rate. Here are some of the key concepts you need to be familiar with to get an understand how modern sleep tracking technology works:
Actigraphy is a non-evasive way of monitoring human rest/activity cycles. It is by far the most common method used for personal sleep tracking devices. In practice this usually consists of a wrist-worn device which measures and records bodily motion.
In contrast to a PSG, actigraphy seeks only to measure a single metric, movement. However because it’s cheap to deploy and can be used in the comfort of your own home it has been a popular tool for researchers for many years.
A 2011 study on wrist actigraphy usage in clinical settings concluded that ” Although actigraphy should not be viewed as a substitute for clinical interviews, sleep diaries, or overnight polysomnography when indicated, it can provide useful information about sleep in the natural sleep environment”
Whilst accelerometer devices are cheap and easy to manufacture, movement is not the most ideal or accurate way to measure sleep behaviour. Hence newer sleep tracking devices are starting to incorporate other ways to measure your vital signs whilst you’re asleep.
The advantage of measuring heart rate for sleep tracking purposes is that you can infer more information about the sleep stages, (ie deep sleep, light sleep and REM).
Although sleep staging can only reliably be measured with an EEG, as Dr Michael Breuss, the ‘Sleep Doctor’ explains, “since each sleep stage has a signature heart rate, while not [a] direct measurement of sleep cycle, I think that this is certainly something that will be much closer than accelerometry”
There are many different methods for measuring heart rate, each with their pros and cons.
- optical sensors (Basis, Pulse) measure your blood flow with light
- bioimpedance sensors (Jawbone) measure electrical activity via the skin
- ballistocardiography (Beddit, Withings Aura) measures the forces associated with heart contraction
- non-contact sensors (Resmed) use radio waves to detect breathing, movement and heart rate
EEG (electroencephalogram -brain activity)
In some ways, personal sleep tracking has taken a step backwards. Up until a couple of years ago, one of the best sleep trackers was the Zeo Sleep Manager, the first ever consumer EEG device Sadly, Zeo ceased trading in 2013, a victim of competition from general purpose devices like the Fibit.
There are other options for EEG based sleep tracking, but the technology is still very much in the early stages.
Kokoon makes a pair of EEG equipped headphones which amongst other things can track your sleep.
Dreem, from neurotechnology company Rythm is an advanced sleep headband that features multichannel EEG sleep sensors and a bone-conducting audio feedback tones to aid deep sleep.
Philips Smart Sleep: one of the most interesting pieces of sleep technology at CES 2018 was the news EEG equipped headband from Philips. With very similar looks and functionality to Dreem, Philips Smart Sleep also features bone conducting audio and accurate sleep monitoring.
Sleep tracking apps
The simplest and most cost effective way to get started is by downloading an app for your iPhone or Android smartphone. Prices range from free to just a few dollars.
The beauty of using an app for sleep tracking is that you don’t have to buy any specialized hardware. The app uses your phone’s built-in accelerometer to measure your movement in bed at night.
The general principle for using standalone sleep tracking apps is simple. Before you hit the sack, make sure the app is turned on (and ideally plugged into the charger in case the battery dies) and simply place your phone under the pillow or somewhere on your mattress. The phone will do all the rest, tracking your body movements as you sleep.
Various apps differentiate themselves with add-on features, such as ‘smart’ alarm clocks – promising only to wake you when you’re in a light sleep-, white noise sounds to sooth you whilst asleep, and audio analysis to monitor noise disturbances or snoring.
But standalone apps have drawbacks. Accuracy is the main issue. For instance a memory foam mattress will respond differently to one with soft springs, hence calibration is problematic. In addition phones have no way of distinguishing your movements from your bed partner, which can result in unreliable data.
Standalone sleep tracking apps may lack sophisticated hardware to give you a detailed analysis of your sleep patterns, but they’re the most cost effective way to start to gain some insight into your sleep habits.
Sleep tracking wearables
The next step up from using a phone for sleep tracking is a wearable.
Generally wearables are multifunction devices that measure other important metrics as well as sleep, including step count, heart rate, calorie intake etc. Hence they provide a more holistic view of your health and wellbeing
Because of this, wearables are more expensive than a sleep tracking apps and they also require you to introduce another gadgets into your life.
The wearables market is dominated by the big names like FitBit, Garmin, and more recently Chinese company Xiaomi. However there are literally hundreds of different models of fitness wearables that offer sleep tracking.
This has led to a huge and varied range of wearable form factors. Here are some of the varied types of wearables that feature sleep tracking functionality.
The biggest category, and the widest range of choice, these are the most popular types of sleep wearables. FitBit has been the market leader in wearables for over 10 years, and last year improved on its sleep measuring algorithms with the updated Sleep Stages app which promise more accuracy in detecting sleep cycles.
Lower priced fitness bracelets will just use an accelerometer sensor to monitor your sleep using movement. However the more sophisticated devices like the Fitbit Charge HR and Garmin VivoSmart ranges also feature optical heart-rate sensors for more accuracy in measuring sleep.
The launch of the Apple Watch in 2014 led to renewed interest in advanced multi-purpose wrist-worn gadgets that can launch their own apps, pair with your smart phone, take calls and do a whole lot more.
But the problem with using a smart-watch-for sleep tracking is the short battery life. This has improved in recent years with products like the sophisticated FitBit Ionic which features a 4 day battery.
Alternatively if you don’t need features like GPS, or LTE connectivity or notifications you can opt for a more classic, feature-sparse smart watch like the Activité range by Withings which looks just like an ordinary analogue watch, but features activity and sleep tracking plus a whopping 2 year battery life.
If you won’t like strapping something on your wrist, how about wearing a ring? Innovations in miniaturisation and battery technology have allowed some wearables manufacturers to pack all activity and sleep-sensing technology into a tiny ring that you wear on your finger.
Oura makes a ‘wellness computer’ that features a processor, and heart-rate, movement and pulse oximetry sensors into a sleek ring wearable. Read our interview with Oura CEO Petteri Lahtela here.
Motiv is another company that makes a ring-based sleep and activity tracker that can even connect with Alexa and your smart home.
Non-wearable sleep tracking options
If you don’t want to wear a wristband in bed or you’re not interested in gathering fitness tracking data, you might want to consider one of the in-bed options for sleep monitoring.
Nokia Sleep is a contact free system to monitor and improve sleep. Borrowing from technology from the Withings Aura, it consists of a sensor which you place under your mattress, which tracks your sleep cycles, heart rate and also if you snore.
The Eight Sleep Tracker is an in-bed sleep monitor that uses ballistocardiography to track your sleep and promises to turn any bed into a smart bed. It’s comprised of a smart mattress cover that’s placed on top of your bed and gives you detailed sleep analytics and the ability to warm your bed to your optimum sleep temperature.
Emfit QS – founded in 1990, Emfit is another Finnish company that manufactures a sophisticated ballistocardiography-based sleep tracker for the bed. The Emfit QS on the surface seems similar to the Beddit, but offers some unique metrics including continuous heart-rate variability (RMSSD) which is super relevant to athletes for optimizing training schedules and monitoring recovery.
Beddit, a Finnish company that was acquired by Apple in 2017 uses a thin-film sensor device which attaches to your mattress. Using ballistocardiography, the sensor claims to accurately measure heart-rate, respiration and movement and the makers provide links to scientific studies based on the device.
Contactless sleep tracking
SleepScore Max is a completely contactless bedside sleep monitor and improvement system.
Made by SleepScore Labs the Max is an updated version of the Resmed S+ (Read our in-depth Resmed S+ review here)
Using low-intensity radio waves, SleepScore Max detects your body movement and tracks your breathing, giving you a detailed analysis of all your sleep stages including REM sleep.
Circadia is another contactless sleep tracker, currently scheduled to arrive in Q2 2018. A collaboration between leading sleep scientists and a team of engineer, Circadia is a modular system for improving sleep quality. It features a wall or table mountable sleep tracker, and a portable light therapy lamp. Read our interview with the Circadia CEO here.
Our Top Recommended Sleep Trackers In 2018
|Type||Features||Price||Where to Buy|
||Contactless bedside monitor||'Invisible' radio-wave sleep tracking, big data sleep insights||***||Visit website|
|FitBit Alta HR
||Activity bracelet||Heart-rate monitor, 5-day battery, Sleep Stages software||**||Read reviews on Amazon|
||Under mattress sleep sensor||Ballistocardiography sensor, IoT integration||**||Read reviews on Amazon|
|Xiaomi Mi Band 3
||Activity bracelet||Value for money fitness/sleep tracker||*||Visit website|
||Wearable pulse monitor||Helps identify sleep apnea, snoring||***||Visit website. Use promo code SLEEPJUNKIES10|
||Smart ring||Advanced wearable for improving sleep||****||Visit website|
|Eight Sleep Tracker
||Smart mattress||Mattress warming pad, Alexa enabled, sleep coaching||****||Visit website|
Polysomnography vs consumer sleep tracking
So, we’ve determined sleep tracking can be useful, but before you rush out to spend your money, you should realise that consumer sleep monitoring solutions, at least for the foreseeable future, will not give you anywhere near the level of accuracy and detail that a specialist sleep centre will provide.
We’ll talk more about how accurate personal sleep tracker are later, but for now, let’s dive into the type of technology you’ll encounter in a professional sleep lab or clinic.
Laboratory based clinical sleep tracking is known as polysomnography. Typically a polysomnogram (PSG) will involve connecting a spaghetti-like mass of wires, tubes and electrodes to various parts of your body.
A single-night PSG can yield a lot of detailed information about your sleep; it’s also how doctors can tell if you’re suffering from sleep apnea.
Poly, meaning many, is a reference to the multiple types of test that run simultaneously while you are asleep. These include:
Brain activity – an electroencephalogram (EEG): multiple electrodes attached to the scalp pickup your brain activity, which determines your sleep stages
Eye movement – electrooculogram (EOG): electrodes attached above and below the eye detect when your eyes are moving, giving an accurate indication of when you are in REM (rapid eye movement) sleep
Heart rate –electrocardiogram (ECG): electrodes attached to the chest measure the electrical activity of the heart as it contracts and expands
Muscle tension – electromyogram (EMG): electrodes attached to the face and legs detect when your muscles relax and contract
Oxygen levels – pulse oximetery is a non-invasive way to measure oxygen levels in the blood
Breathing/air flow – sensors attached below the nostrils can detect any breathing abnormalities
Microphone – to record frequency and volume of snoring activity
One criticism of polysomnography is that the process itself can interfere with normal sleep. Spending a night in a hospital like environment, hooked up to dozens of wires is not most peoples’ idea of a restful sleep environment.
How accurate are personal sleep trackers? (updated Nov 2018)
We’ve already established that personal sleep tracking pales in comparison to a PSG in a sleep lab. But exactly how well do they compare? It’s a difficult question. The consumer electronics industry moves very fast. Peer-reviewed science on the other hand takes a long time.
A 2012 study comparing a Fitbit activity, standard actigraphy, and PSG found the movement trackers had a tendency to “consistently misidentify wake as sleep and thus overestimate both sleep time and quality.”
However, such scientific papers become out of date as soon as a new gadget is released on the market.
Perhaps a more useful comparison is sleep specialist Dr Christopher Winter’s piece in the Huffington Post in Feb 2014. He took upon himself the task of evaluating 5 different sleep trackers, worn simultaneously whilst undergoing PSG in a sleep lab. In his test, the Basis tracker was the most accurate, with Jawbone and Fitbit devices performing less well. 24/7, a sleep tracking app for the iPhone came out worst in the test. You can view the results in the graph below.
Consumer technology moves faster than research
In more recent studies, researcher have taken consumer sleep wearables into the lab, and if you’re interested in the cold hard data, they are definitely worth a read. Here are some links to recent comparisons of personal sleep trackers with both medical grade actigraphy devices and polysomnography:
Measures of sleep and cardiac functioning during sleep using a multi-sensory commercially-available wristband in adolescents. (2016)
Takeaways: “FitbitChargeHR™ showed good agreement with PSG and ECG in measuring sleep and HR during sleep, supporting its use in assessing sleep and cardiac function in healthy adolescents.”
The Sleep of the Ring: Comparison of the ŌURA Sleep Tracker Against Polysomnography (2017)
Takeaways: ŌURA ring had a 96% sensitivity to detect sleep, and agreement of 65% in detecting light sleep (N1), 51%in detecting deep sleep” (N2 + N3), and 61%in detecting REM sleep.
Comparison of Wearable Trackers’ Ability to Estimate Sleep (2018)
Takeaways: “Some of the wearable trackers (Jawbone UP3, Fitbit Charge Heart Rate, and Garmin Vivosmart) resulted in closer approximations to self-reported sleep outcomes than a previously sleep research-grade device, these trackers offer a lower-cost alternative to tracking sleep in healthy populations. As technological advances in wearables will constantly offer more feasible and reliable alternatives for measuring sleep patterns, researchers and practitioners need to be informed on the comparability of these wearable trackers that have significant potential for research and practical applications for measuring sleep.”
So, on the face of it, there’s some good news, at least with regards to these three studies. It seems that there is an argument that consumer sleep trackers can detect sleep reasonably well, compared to both medical actigraphy devices and PSG. The same cannot be said for detecting wakefulness, or detecting sleep stages.
The big problem in this type of research however was summed up by Max de Zambotti
lead author of the Oura Ring study. Zambotti remarked that in these types of studies ‘science’ will always be several steps behind the technology, because commercial innovation happens at a much more quickly than the glacial rate of scientific research. Here’s what Zambotti had to say on a LinkedIn post in 2015:
“It is clear that the wearable market move faster than steps and processes involved in publishing scientific papers. As a consequence, research evidences about the validity of a specific devices in tracking sleep is available when a product is already out of market. Following that, like for standard actigraphy, any potential validation of wearables needs to be done in different populations, age ranges, etc. All these aspects further delay the validation of a device. In few words, we will know some information about the validity of a specific model of a specific brand when the same company will already release new devices several generations ahead of the one tested!”
Sleep tracking and your data
One of the ironies about the quantified ‘self’ movement, is that by uploading your tracking data to any of the ‘cloud’ providers, you by default waves any rights to sole ownership of your personal data.
Aggregating ‘big data’ from users has become the de-facto business model for technology companies. Although you give it away for free, your personal data holds great value for the giant databases Apple, Google, et al – in terms of both commerce and research.
For example, Jawbone recently published a fascinating set of reports, based on tens of thousands of UP wristband users. Among the findings we learn that Toyko is the most sleepless city, averaging 5h 44min, and Swedish people are the biggest walkers.
This kind of data may seem innocent and benign on the surface, but the potential value is immeasurable to an array of interested parties, be they pharmaceutical companies, insurers, doctors or even employers.
So it’s important to ask yourself the question – do you feel 100% comfortable sharing your data online?
The future looks bright for sleep tracking. With tech giants Apple and Google pushing their health platforms, and a wearables industry about to explode, a lot of people over the next couple of years will be tempted to join the legions of quantified selfers already out there.
But some doubts and questions remain about the long term viability of such technology. What happens once you’ve ‘diagnosed’ your sleep problems or made adjustments to your lifestyle to correct bad habits? Will people want to continue monitoring themselves for the sake of it or will your wristband be consigned to the bottom drawer after six months?
Whether or not sleep tracking becomes a fad or goes mainstream, it’s hard to feel negative towards a movement that is surely destined to raise awareness about the many life-enhancing ways that sleep can benefit our daily lives.
Jeff is the founder and editor-in-chief at Sleep Junkies . A passionate sleep advocate, he started the site in 2012, reaching millions of readers across the globe. Jeff also runs the product curation platform SleepGadgets.io . He is often asked to speak at about current trends in consumer sleep technology at various events.