Sleep tracking has become one of the most important features, whether you’re sporting a cheap fitness tracker or high-end smartwatch. Sleep tracking isn’t just a nice-to-have, it’s now a staple feature.
And that’s hardly surprising – there’s been a lot of research and media interest about the importance of sleep, with studies suggesting not only are most of us not getting enough sleep, but also that it plays a huge role in ensuring physical and mental health.
Read this: What are the best sleep trackers?
Advances mean that trackers can now identify different stages of sleep, present you with more useful information and even suggest what you can do it improve your sleep.
But despite increased accuracy and interest, can the sleep tracking features in your favorite wearables actually help you to make significant and sustainable changes to your sleep? We find out.
How do wearables track sleep?
Every wearable device employs a slightly different sleep tracking method, but most don’t just track your sleep. Instead, they keep tabs on what your body is doing as you sleep to get the best guess about when you’re awake, in deep sleep and when you wake up during the night.
The easiest way for a wearable device to tell when you’re sleeping and when you’re awake is by tracking movement. Many trackers and smartwatches contain sensors built to detect movement, like an accelerometer, which is how the tracker also measures the steps you take throughout the day.
With that in mind, devices that detect sleep solely by using a movement sensor tend to be those that are a little older, like the Jawbone Up, Fitbit Flex and Misfit Flash, as well as those that are the simpler, cheaper options from your favourite brands, like the Fitbit Inspire, the Garmin Vivofit 4, and wearables aimed at children, like the Fitbit Ace and Garmin Vivofit Jr. 2.
These sensors can detect the subtle movements you make throughout the night to pinpoint when you go to sleep, the time you spend asleep, and when you wake up. Movement sensors can also detect whether you’ve had a restless or restful night’s sleep, and can sometimes tell you how many times you woke up during the night too.
This is a simple way to track your sleep, as movement is only one factor that determines whether you’ve had a good night’s sleep or not.
It’s an easy way into sleep tracking and gives you simple data. But if you’re wanting more, then you’ll need something with heart rate monitoring.
Tracking heart rate
Most of the newer, more expensive trackers and smartwatches tend to use other methods to track your sleep – the main one being a heart rate monitor, to measure your bpm as you rest.
Trackers then use this data to estimate either your beats per minute (BPM), your heart rate variability (HRV), as well as your resting heart rate (RHR) – or all three. This helps their algorithm to figure out not just when you’re likely sleeping or awake, but which sleep stages you’re in, whether that’s light, deep or REM.
A lot of the latest Fitbit devices, like the Fitbit Versa, Fitbit Ionic and Fitbit Inspire HR provide some of the most detailed and accurate information about sleep stages.
In fact, Fitbit tested its sleep stages tracking against polysomnography technicians, which are the best ways to track sleep, and found it was 69% accurate.
Although Fitbit’s sleep tracking is our gold standard, Garmin also introduced a feature that identifies different sleep stages to the Garmin Connect, which works with more recent devices, including the Vivoactive 3, Forerunner 645 and Fenix 5.
You can also find a similar level of detailed data in the apps of many of the top wearables right now, including the Oura Ring, the Withings/Nokia Steel, the Polar M430, as well as the Xiaomi Mi Band 3 and the Honor Band 4.
Although not native to the Apple Watch, there are also many third-party sleep apps on your Apple Watch that can serve up this kind of information too, using the device’s heart rate monitoring, such as the Pillow Automatic Sleep Tracker or AutoSleep.
This kind of sleep tracking is a big step up from movement because it’s not only more accurate – we’ve tried some devices that can get sleep and wake times wrong – but it shows you the different stages of your sleep.
Data about sleep stages is useful because it could explain why you’re feeling more sluggish – maybe because you didn’t get enough deep sleep? Or it could hint at changes you could make to your routine, environment or anything else. For example, a lot of light sleep could mean you need to create a better sleeping environment in your room.
There aren’t any major drawbacks to this kind of tracking, but some people find that detailed data about sleep stages can be a bit overwhelming at first, and they don’t know how to interpret it. This is why brands that provide feedback, advice or insight about sleep stages could have the biggest impact on your sleep, we particularly like the data presented by Fitbit’s sleep stages, as well as the Oura ring.
It’s worth mentioning that a number of other devices, which we wouldn’t class as wearables, can also track your sleep using your heart rate data. However, rather than using a heart rate monitor, they use ballistocardiography (BCG).
This is another way of measuring your heart rate by observing the way your body moves, rather than being attached to your skin. Some of the sleep tracking devices that consist of a strip that lives under your mattress may use a BCG sensor, such as the Emfit QS HRV Monitor.
Tracking the rest
While we’re mentioning mattress devices, it’s also worth taking a look at what a few other standalone devices, that’s those not attached to your wrist, can track. As you’ll see, movement and heart rate tracking are only part of the puzzle.
For example, Beddit slips under your mattress and tracks heart rate, as well as your breathing, snoring and room temperature. Similarly, the Withings Sleep (essentially a rebranded Nokia Sleep) tracks all of that same data, as well as the intensity of your breathing disturbances, which means it can help to identify signs of sleep apnea.
The focus on sleep apnea is currently only available for standalone devices, like the Withings/Nokia Sleep, but we expect it’ll be coming to some of our favourite wearables soon and bolstering their sleep offering.
For example, the Fitbit Versa and Fitbit Charge 3 are built with the tri-wavelength sensor on board, making relative SpO2 tracking/sleep apnea detection something that should come to devices in the near future.
Although these standalone devices can track a lot of data – and serve up very detailed graphs when you wake up – this level of detail is sometimes too much for those who want to just improve their sleep a little but don’t have time to interpret graphs. They’re definitely aimed at those who want to focus on sleep and nothing else. For those who are also interested in fitness or activity tracking, we’d recommend sticking with your wrist-based wearable.
How to use sleep trackers to improve your sleep
Different devices can show you different kinds of information about your sleep. Whether that’s just when you’re awake or sleep, the sleep stages you’re in or something more specific. But can this information ever noticeably improve your sleep?
One of the main reasons that tracking sleep can improve its quality is because it gives you more awareness. “Tracking any aspect of health, whether it’s sleep, diet, exercise, or anything else, can lead to changes,” says Dr Grandner, Director of the Behavioural Sleep Medicine Clinic at the University of Arizona. “You may notice patterns, or identify problems you didn’t know were there just by seeing what you are doing.”
For example, if you’re having trouble sleeping and then you’re shown that you get up a lot in the night, you could tweak your routine, try some different ways to get to sleep or notice something specific, like that you don’t sleep well when you go to bed too late – these could be simple fixes.
Essential reading: What your sleep tracker’s metrics actually mean
“Using a tracker can help people identify their patterns and improve their sleep,” Dr Kelly Baron, Associate Professor in Family And Preventive Medicine at The University of Utah, tells us. “Using my tracker, I learned that if I don’t go to bed before 10:30 pm, I never get even close to the 7 hrs that I’d like to sleep each night. It may seem obvious but seeing the pattern really helped me.”
What this means is, you don’t always need a top of the range tracker in order to keep tabs on your sleep. Sometimes those that just help you monitor the duration of your sleep and the time you went to bed could help. This also means, if you have a more detailed device, you don’t need to delve into your sleep stages data every morning – it might be a waste of time.
You’ll find this kind of information in practically every wearable on the market these days, from the Fitbit Inspire through to the Garmin Vivoactive 3 Series at nearly triple the price.
However, to notice these patterns and build your awareness, it’s up to you to look at your sleep data and pay attention to what’s working and what isn’t when you make changes – luckily a tracker can help with this too.
“You need to prioritise sleep and shift things around to make enough time for sleep,” Dr Baron says. “I think a tracker can be helpful at seeing your progress and encouraging change.” In this way, not only can your tracker help you to identify patterns and areas to change, but it can encourage you when you see tweaks to your routine or lifestyle paying off with longer, better quality sleep.
Because monitoring data is important, we recommend picking a wearable that has an app you like that presents your sleep graphs in a way that works for you. For example, Fitbit relies on colourful graphs and a simple, intuitive display. The Oura Ring has a dark interface with a focus on lots of bar charts, whereas Garmin Connect tends to have a sportier, more detailed look.
Read next: How Apple could top Fitbit’s sleep tracking
But the sticking point here is – you need to be dedicated to making changes. Your tracker can’t do the hard part for you. Both experts tell us that a tracker is like weighing scales, it can measure changes, but it’s your actions that help you lose weight or get better sleep. “Many people need more than just measurement,” Dr Grandner says.
As many of you know, making lifestyle changes, especially those that have become habitual, is much easier said than done. So can a tracker make long-term behaviour change easier?
The experts we spoke to agreed that for a tracker to actually help you change beyond raising your awareness, it would need to provide you with in-app insights, personal data and even tips or suggestions – the problem is, few do this well.
“Some apps do more than just provide feedback,” says Dr Grander. “Those that are helping users make the most of their data and make some behavioural changes are ahead of the curve.”
“For example, just telling people to go to bed earlier is not likely to be helpful for a number of reasons,” Dr Grandner tells us. “It’s a recommendation without any insight into the person’s actual needs and the barriers they are facing. Instead, you need to know what to do with the information and how to interpret it.”
We’ve found that Fitbit’s sleep stages provide useful feedback, telling you why you might be in certain stages of sleep – and what you can do about it. You can also look through your 30-day average sleep, as well as get access to a ‘benchmark’ feature, which shows how your sleep compares to people of a similar demographic.
You’ll get similar helpful insights from the Oura Ring, the Polar M430 and Garmin Connect. But we think the Fitbit’s Sleep Stages are our favourite for both detail and accessibility.
Taking a more holistic approach
Another way to get more from your sleep tracking is to pick up a device that keeps tabs on how everything that happens throughout the day, like your physical fitness, heart rate, diet and stress could be affecting your sleep – then attempts to join the dots.
Right now, the Oura Ring is one of the few devices that provides this kind of holistic approach, which shows how your activity and ‘readiness’ levels could impact on your sleep, as well as providing clear bar charts about which parts of your day-to-day routine need more attention. It’s devices like this that Dr Baron thinks will be the future of sleep tracking, making it much more useful.
“Trackers need to provide a more cohesive picture of someone’s behaviour,” she explains, “linking sleep to diet, exercise, and even social activity and location.”
Setting realistic expectations
The most important thing to remember is that a sleep tracker can, for the most part, only track. Which means you need to get real when it comes to your expectations about what it can do for you.
“The ability of a device to help depends on what you are using it for,” Dr Grandner tells us. That means you need to be clear on what you’re hoping to achieve from sleep tracking – do you want to know why you’re feeling sluggish? Are you interested in optimising your activity and your sleep and just want more awareness? Or are you concerned you have a big sleep problem? Asking yourselves these questions will help you to use your tracking device in the right way.
Dr Grandner stresses that you need to decide what you want to fix first. “Fixing a sleep disorder? Probably not very helpful,” he says, “learning more about your sleep? Probably helpful. Making changes to your sleep for the better? There is a lot of unknown here.”
Furthermore, Dr Baron urges you to take the sleep results trackers give you with a pinch of salt. “The algorithms are proprietary and validation of these devices are rarely published,” she says. “Trackers are useful to look at trends in your own sleep but just because it said you slept x hours, doesn’t mean that’s the absolute truth.”
As you might expect, in the future both experts tell us they want to see more personalised insights, holistic approaches to tracking, accurate readings and recommendations that can help you make long-term changes.
“I think that measurement will be more accurate,” Dr Grandern says. “I also think that more behavioural tools will be added to tracking systems so that people can make improvements to their sleep, beyond just measuring it.”