A Guide To Tracking Your Sleep

"Quantimetric Self-Sensing" apparatus, 1996
“Quantimetric Self-Sensing” apparatus, 1996

Have you ever been curious about your personal sleep habits? Ever wondered whether you’re getting your full quota of rest every night?

Well now there’s no need to be kept in the dark – personal sleep tracking has hit the mainstream. And although the technology is still in its early days, it looks like it’s here to stay.

So, we’ve put together a definitive guide for anyone who wants to find out about personal sleep tracking technology. We hope you enjoy.

The quantified self

[toc] The last few years has seen an explosion of interest in gadgets and software designed to measure and evaluate our sleeping habits. Many factors have contributed to this – a growing awareness of sleep as a health concern, the ubiquity of smartphones, the rise in ‘big data’ analytics, a trend towards personalised healthcare – plus, of course, our inherent curiosity about ourselves.

The rise in sleep tracking stems from the phenomenon known as the ‘quantified self’ – a term used to describe those who use technology to collect data about themselves for personal development and to increase self-knowledge.

‘Self-tracking’ technology used to be expensive, bulky and complicated to set up. But Moore’s Law and the mass adoption of smartphones has changed all that. Nowadays millions of people are using gadgets to monitor aspects of their daily lives, including exercise, diet, heart-rate, location, alertness, mood, productivity and of course, sleep.

Why quantify?

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. Instead of relying on contemplation or intuition, ‘quantified-selfers’ have access to cold hard data.

Gathering and analysing this data, over time, gives individuals great insight into whatever aspect of their lives they want to improve. Whether it’s getting fit, losing weight, getting smarter, or even curing disease, there’s most likely an app or a gadget out there to help you.

Why track 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.

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.

Eating healthily and staying fit involve making conscious decisions. We can choose between having a salad or a burger, or taking the stairs instead of the escalator. But how do we know if the quality of our sleep is having an effect on our health?

Thankfully, sleep tracking technology 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? Am I getting enough deep sleep, light sleep or REM? In addition

This information is compelling on its own, but if you’re serious about improving your health and well-being it can be invaluable when acted upon.

Sleep tracking – how the professionals do it

How the professionals do sleep tracking
Polysomnogram patient

So, we’ve determined sleep tracking can be a force for good, but before you rush out and buy the latest gadget, it’s useful to take some perspective. Home sleep monitoring solutions, at least for the foreseeable future, will never give the same level of accuracy and diagnostic detail that a specialist sleep centre will provide.

The reason is simple. Consumer sleep tracking products are designed for a mass audience, often with value and simplicity a key part of the design ethos. A sleep centre clinician on the other hand is concerned with getting the most accurate medical diagnosis from his equipment.

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:

Brainwaves – 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 rateelectrocardiogram (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.

However it’s important to recognise that for now at least,  it’s not possible to produce the same level of diagnostic testing with consumer focussed technology. Home based sleep tracking may have the advantage of low cost and convenience it’s not a substitute for medical advice.

How accurate are personal sleep trackers?

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.
Sleep trackers compared with polysomnogram (PSG)

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 – sensing your movment

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


accelerometer photo
Accelerometer chip

At the heart of every actigraphy device is something called an accelerometer. Using MEMS technology, these tiny components act as sensors, converting movement into electrical signals.

Once prohibitively expensive, accelerometer chips can now be manufactured for cents. Hence accelerometers can be found everywhere today; in your Iphone, your washing machines, and even shoes.

Beyond accelerometry

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.

Heart rate

The advantage of measuring heart rate for sleep tracking purposes is that you can infer 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 (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.

Neuroon, is an intelligent sleep-tracking eyemask (check out our detailed Neuroon review here) that features EEG, EMG and EOG sensors. Their latest product, Neuroon Open is an updated version of the original mask, but with fully open-sourced firmware, algorithms and hardware schematics.

Sleep Shepherd is another Kickstarter funded project – a headband which uses third-party EEG sensors to track your sleeping brain, and facilitate restful sleep with the help of ‘binaural tones’.

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.

Internet of Things (IoT)

The internet of things (IoT) is a concept of a world where everyday physical objects are equipped with network connectivity, allowing communication over the internet.

IoT has been happening for decades but smart, cheap sensor technology is now enabling it to become mainstream. From setting your thermostat, to monitoring global pollution, the internet of things will impact all of our lives.

Fitness and sleep tracking is another application of the IoT. Many devices already let you upload your sleep statistics to the internet for analysis. In the future, it’s likely we will see even more integration and connectivity between personal tracking hardware and ‘cloud’ software.

For example, both Jawbone and Fitbit, two of the market leaders in fitness tracking, have a software-platform which allows 3rd-party hardware to integrate with its software.  Similarly, Apple’s Healthkit and Google Fit platforms enable manufacturers and developers to access their services, allowing you to store all your health, fitness and sleep data in one place.

There’s no doubt we’re about to witness an explosion in interconnected devices and apps geared towards health, fitness and sleep. Whether we like it or not, the Internet of Things is here!

Types of sleep trackers

Sleep tracking apps

sleep tracking appsThe 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.

There are literally hundreds of sleep-related apps available for Apple and Android devices. Four of the most popular at the moment  are Sleep GeniusSleepCycleSleepBot and Sleep Time.

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.

Wearables and fitness trackers

wearable sleep trackersThe next step up from using a phone for sleep tracking is a wearable activity tracker.

‘Wearables’ usually combine sleep tracking capabilities with other functions including as fitness monitoring, calorie intake and heart-rate monitoring.

According to industry analysts, the world is about to go crazy for wearable technology.

Tech giants Apple, Google, Microsoft and Intel have poured lots of money into wearable devices, whilst Morgan Stanley have predicted that the business could be worth a staggering $1.6 trillion in the near future.

It’s easy to see why. The applications for wearables are incredibly diverse including communications, healthcare, fitness and wellbeing, home automation and even mobile payments. But there’s a problem at the moment. Over 50% of people who buy a fitness tracker or similar device, eventually lose complete interest

Why such a high drop-off rate? Users cite many problems; short battery life, poor design, tricky software, but essentially the technology is not yet mature enough to warrant mass adoption. Maybe this will change. Certainly there are no shortage of products to choose from. Although there are some exceptions, most wearable technology at the moment come in the form of wrist-worn actigraphy devices.

There are literally hundreds of different models on the market and many more in development. But this competitive market is currently dominated by a handful of companies who are leading the way in wearable fitness and sleep tracking. Here’s a brief rundown:


fitbit ionic sleep tracking smart watch
The Fitbit Ionic sleep tracking smart watch

The launch of the Apple Watch  in 2014 led to renewed interest in advanced multi-purpose wrist-worn gadgets. But are smart watches suitable for sleep tracking?

The main problem for a watch-based sleep tracking solution is the short battery life. Aesthetics are important too. Not everyone wants to sport a ‘techie’  looking device on their wrist.

There are alternative’s however. The Activité range by Nokia (formerly Withings), a Swiss watch maker, looks just like an ordinary analogue watch, but features activity and sleep tracking plus a whopping 2 year battery life compared to the meagre 24 hours Apple’s watch will give you.

Bed-based sleep tracking options

Nokia Sleep tracker
Nokia Sleep under mattress smart sleep sensor

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,  a company Nokia acquired in 2016, 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 has created 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. (edit: Beddit was acquired by Apple in May 2017 – watch this space for more details!)

Contactless sleep tracking

SleepScore Max contactless sleep tracker
SleepScore Max by SleepScore Labs

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.

Sense, the popular orb-like bedside sleep tracker by Hello Inc….. is no more Read how Hello ceased trading in June 2017

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 self’ers 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.

[expand title=”Photo Credits”]

Photo by SparkFunElectronics

QuantimetricSelfSensingPrototypeMann1996inset  via Wikimedia Commons

Photo by Todd Huffman

Photo by Jason A. Howie


This article was originally published at Sleep Junkies