The Real Reason Apple Watch 5 Doesn’t Track Your Sleep

Apple watch being held dark

On 10th September 2019, after the customary level of hype and anticipation that we have all come to expect from Apple product launches over the years Apple Watch Series 5 ( was released. Truth be told, with the exception of the new Always-On display and built in compass, it wasn’t really much of an upgrade from Apple Watch 4. But there was one hoped for and expected feature that was surprisingly still absent… Sleep tracking.

Why Track your Sleep?

Before we take a look at why sleep tracking remains absent from the Apple Watch range, just why would you want to track your sleep in the first place? Put simply, getting good quality sleep is the single most important thing you can do to live a healthy life. And the list of benefits is long; from body-wide healing, weight loss and reduced stress to improved memory, reduced inflammation and risk of depression to name a few.

The Science of Sleep Tracking

So, sleep is important. But what exactly should we track? If we take sleep laboratory tracking as a guide, we should consider the following parameters:

  • Breathing Rate
  • Heart Rate
  • Body and Leg Movements
  • Eye movements
  • Blood oxygen levels
  • Sleep Positions
  • Brainwave Patterns

If you were to visit a sleep clinic and undergo the gold standard of sleep analysis known as polysomnography, the information above would be gathered together and assessed to determine the possible presence of a sleep disorder. And a fundamental part of this type of sleep study would be the last on this list; monitoring of your brainwave patterns. This component would be crucial not only to track the stages of your sleep, but also your sleep cycles. As you will see below, whilst there are a number of possible indicators of the stage of sleep we are in, the only way to be certain is through brainwave measurement.

Apple watch pink

The Stages of Sleep

Normal sleep consists of two main stages; rapid eye movement sleep (REM) and Non-REM sleep. These are characterised by distinct signature brainwave patterns and neuronal activity. When you fall asleep you begin Non-REM sleep, which follows three stages from light into deep sleep, before you then move into REM sleep. During stage 1 Non-REM sleep, heart, breathing rate and eye movements all slow down and your muscles relax. During stage 2 this slowing down increases, aside from brief bursts of increased brainwave activity. Stage 3 Non-REM sleep is a critical phase for health and wellbeing, and consists of deep restorative sleep. During this phase, everything slows down and it becomes difficult to wake you. 

A complete sleep cycle consists of all these stages of sleep and lasts approximately 90 minutes, concluding with the fourth and final stage, REM sleep, which is characterised by rapid side to side eye movements behind closed eyelids, together with brainwave activity, breathing and heart rate which is similar to waking levels. During REM sleep, arm and leg muscles become temporarily paralysed, which prevents you from acting out your dreams. Following REM sleep your brain returns to stage 1 Non-REM sleep for another sleep cycle. In general, sleep cycles early in the night have shorter REM periods and longer Non-REM deep sleep. Later in the night, the REM periods become longer and time spent in deep sleep decreases.

Why Doesn’t Apple Watch 5 Track Sleep?

So, given how important sleep is to our health and the science of sleep tracking is well established, just why would Apple omit this feature? Could it be that they felt the battery life wasn’t sufficient to track sleep data all night. That the design wouldn’t be sufficiently comfortable for users to wear in bed? Or perhaps they sensed that the trend is fading and people were moving on from a desire to track their sleep?

Well, there is another reason, and that reason is the Apple Watch 5 cannot measure brainwave activity. Apple could have just done as all the other mainstream sleep trackers have done, and track indicators of sleep. And they may still. But the problem with this is, if you really need to track your sleep they just don’t work well enough.

Let me explain why...

How Do Sleep Trackers Work?

Many of the current crop of sleep trackers are worn on the wrist, including Fitbit Versa, Withings Steel, and Garmin Vivosmart. There are plenty of others that do things a little differently, such as the Oura ring, BeautyRest and Emfit QS, but the principle is still the same. They all measure indicators of sleep, not accurate stages or cycles of sleep ( These mainstream sleep trackers are not capable of measuring brainwaves, and when it comes to accurate sleep tracking, that is a big issue. We will look at why this is the case in a moment but first let’s look at what they do measure.

Sleep tracking

How Do Sleep Trackers Measure Sleep?

Current wearable sleep trackers obtain a large amount of their data using something called an accelerometer, which measures the amount of movement that occurs during sleep. This process is called Actigraphy. The idea behind this approach is that we move in characteristic ways when we are awake, and we generally move less when we are asleep, aside from rolling over and twitching. Non wearable sleep trackers mainly use a technique known as Ballistocardiography, with sensors contained in thin strips designed to gather data such as movement, heart rate, breathing and heart rate variability.

These approaches may sound like simplistic ways to measure such a complex activity as sleep. But they do have some merits and if you already sleep well they are pretty accurate for calculating total sleep time, and sleep percentage ( . For this reason, Actigraphy has been used for a number of years. After all, it is a lot less expensive than traditional lab quality tracking, and also less intrusive. It has historically been the preferred method for sleep tracking in the natural home environment and so many manufacturer’s have used this as the basis of today’s wearable sleep tracking technology. No brainwave detection, just a measurement of sleep indicators. However, there are a few crucial problems with this approach:

Movement.As we have seen, current sleep trackers use movement as a key indicator of your sleep cycle. But, if you happen to wake often in the night, lie still whilst counting sheep in a desperate attempt to drift off, or enjoy a two hour Netflix binge in bed prior to turning out the light, your sleep tracker will be none the wiser and simply record your inactivity as restful sleep. Not very helpful if you really need to know what is wrong with your sleep and how to improve it.

Sleep trackers only work if you already sleep well, which essentially defeats the purpose. One of the main concerns highlighted by researchers looking into the accuracy of sleep trackers ( was that errors were highest in those who didn’t sleep well. So, unless you are already a great sleeper and you want to gloat about it, current sleep tracking technology is not up to the job of helping you get better sleep.

Sleep stage tracking.As we’ve discussed above, current sleep trackers only track indicators of sleep, not the most important part which is brainwave activity. Without brainwave tracking, sleep stage tracking is just guess work and nothing more. Somewhat worryingly though, this fact hasn’t actually deterred manufacturer’s from making such sleep stage claims. Perhaps Apple have thought twice about it…

For wrist sleep trackers, there is also the added problem of when to charge the battery. If you are wearing your Fitbit during the day to track your activity, when are you going to charge it if you also wear it through the night? Even with industry leading battery life, day/night still tracking requires regular battery charging, and that means time away from you and loss of precious tracking data.

So, all is not quite what it appears in the mainstream sleep tracking world, and it would seem that Apple are wise to this. They are not traditionally the first to implement new features into their technology, as owners of android phones will happily testify. And when it comes to sleep tracking, which has been featured by many of their competitors for years, Apple appear again happy to wait and let other third party app developers take the Apple Watch sleep tracking reins for the time being.

How to Accurately Track and Improve Your Sleep Now

At Well Professor, whilst we closely follow all the mainstream wearables trends, we also look beyond this and utilise our years of industry experience to discover the technology you may not yet know about. And when it comes to sleep tracking, things have already moved on. A long way. You probably haven’t heard of it yet but with Dreem 2, it is possible to accurately track your sleep in the comfort of your own home using unrivalled lab quality brainwave analysis at an affordable price. ( Dreem 2 tracks your sleep for a full 7 days using this technology, before setting about changing things. Once it has carried out a complete analysis of your sleep, it sets about improving and optimising things using tailored cognitive behavioural therapy for insomnia (CBT-i) programmes, and precise sound stimuli. You see, with Dreem 2 sleep tracking is merely just the beginning. What really matters is what comes next; a fundamental transformation of the way you sleep, the quality of your sleep, and the inevitable benefits on your health now and long into the future. 

So while Apple waits, you don’t have to. Dreem 2 is the future of your sleep. And you can start now...

Read the Dreem 2 review

Samuel Maddock is a registered osteopath and health technology researcher. He has over a decade’s experience researching the latest innovations in health and wellness technology and consulting for health technology manufacturers to help improve product quality and effectiveness.