How Do Sleep Trackers Work And Are They Reliable?

photo of me wearing a sleep tracker in bed

You spend around a third of your life asleep, with the amount and quality of sleep having a huge impact on the rest of your life.

So it’s natural to be curious about how long you really sleep for, and whether you’re getting enough good quality sleep without any sleep disorders to address.

Until recently your options for assessing your sleep were somewhat limited: you could keep a sleep diary; ask your partner about your sleep; or record yourself sleeping.

The only way to accurately assess your sleep would be to visit a specialist sleep clinic. But now there’s another option to improve your accuracy of self-assessment: the personal sleep tracker.

A question of accuracy

How do they work though, and how do they compare to the equipment available in a sleep lab? And can you actually rely on the information they provide?

These are important questions to consider, especially if you’re thinking of spending a fair bit of money on one.

I’ve been conducting an ongoing sleep tracker review, testing wearable and non-wearable devices. And what I’ve come to realize is that there’s quite a range in terms of what they measure, and how they do it.

So I decided to investigate what researchers have to say about the accuracy of both the devices themselves and the technology behind them.

Hopefully, this article will give you a better understanding of what you can expect from your sleep tracker. And how much you can trust all the information about your sleep they claim to provide.

How sleep specialists measure sleep

To understand the strengths and weaknesses of personal sleep trackers, it’s useful to first take a look at how specialist sleep centers measure sleep.

If your doctor suspects you have a sleep disorder, they might refer you to a sleep clinic for a sleep study, known as polysomnography (PSG).

This typically takes place over a night or two, with different pieces of equipment measuring your sleep stages and cycles. Someone will usually observe you while you sleep as well, and so a lot of information is gathered about your sleep, including:

  • Brain waves (EEG).
  • Breathing, including how easily or not you breathe, how often you stop breathing and for how long.
  • Heart rate and rhythm.
  • The flow of air in and out of your lungs.
  • Muscle activity.
  • The positions you sleep in during the night.
  • The movement of your eyes.
  • Oxygen levels in your blood.

All of this information is then used by the sleep specialists to assess your sleep and diagnose any sleep disorders. It’s easy to see then why polysomnography is often referred to as the gold standard of sleep monitoring.

Logically then, it’s hard to imagine how a small sleep tracker worn on the wrist could possibly do the same as all these high-tech and expensive machines.

So I think it’s useful to bear this in mind when it comes to the expectations you might have of your personal sleep tracker. It also leads to an important question: if personal sleep trackers can’t measure all of those factors, what exactly can they reliably do?

As you’ll see later, they can be relied on to measure some basic sleep information, such as the total time you spend asleep and how often you wake up in the night. To understand what they can actually do though, let’s first take a look at the technology inside the trackers and what it’s capable of.

The science behind wearable sleep trackers

One of the key measuring tools of wearable sleep monitors is called actigraphy. Actigraphy essentially involves recording movement through a measuring device called an accelerometer.

The idea is that a certain amount of movement corresponds with being awake, and periods of being still corresponds with being asleep.

It has in fact been used by sleep clinicians for 30 years to measure sleep. Even though polysomnography is the gold standard for sleep measurement, actigraphy also plays an important role, especially as polysomnography isn’t without its own issues.

When a patient is hooked up to multiple machines with around 20 electrodes placed on their head, and in a lab rather than their own bed, they understandably might not sleep normally.

So not only is actigraphy less expensive than polysomnography, but people can wear a device in their own home for a week or two, giving a more natural insight into their sleep than just one or two nights in a clinic.

The key questions though, especially if personal sleep trackers depend on it, are how accurate is wrist actigraphy, and what sleep information can it accurately measure?

Fortunately, there’s been a fair bit of research into those two questions.

How accurate is wrist actigraphy?

In 2011, Martin and Hakim published some fascinating research into the accuracy and usefulness of wrist actigraphy for sleep assessment. Importantly, they looked at how actigraphy compares to key forms of sleep assessment:

  • Clinical interviews and sleep questionnaires.
  • Daily sleep diaries.
  • Laboratory Polysomnography (PSG).
  • Videosomnography in children.

They state that wrist actigraphy is useful for assessing sleep in a natural environment, rather than in a laboratory setting. However, they do advise caution against relying on it solely:

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 and/or when extended monitoring is clinically indicated.

In their research, they go on to say that wrist actigraphy can be quite accurate when it comes to estimating information such as total time asleep, sleep percentage, and how long after sleep waking occurs.

However, they also state that the main limitation is mistaking being awake and motionless for being asleep. This could then make it difficult for those who wake many times, or with severe insomnia, and who tend to lie still in bed awake rather than move about.

This is also one of the key points which consumers complain about with commercial sleep trackers. Looking at online customer reviews, for example, will turn up many complaints that time lying in bed watching television or reading a book was recorded as being asleep.

Comparing two types of assessment

Looking at more recent research, in 2013 researchers in the United States also looked into the accuracy of wrist actigraphy compared to polysomnography. They found very similar results to the 2011 research, concluding:

…we conclude that wrist actigraphy with current algorithms is of value for individual-level estimates of both sleep duration and wakefulness after sleep onset

They also mention the idea that results from actigraphy might help people get an objective measure of their sleep, especially when having treatment for insomnia for example. Considering many people tend to underestimate how long they sleep for, this could help them see that the treatment is in fact helping.

Another comparison

Another research study published by Terri Blackwell in 2008 compared actigraphy with polysomnography in older women. She cautions that the more disrupted the sleep, the less accurate the sleep tracking. However, she did find that actigraphy is reasonably accurate for people to use in their homes:

Actigraphy does not replace polysomnography in sleep estimation, but was a convenient, affordable and accurate method of collecting measurements of sleep in a large epidemiologic study of older women.

So it seems that although wrist actigraphy does have some limitations, it’s definitely very useful. And it does appear that many manufacturers of sleep trackers are aware of the limitations.

To try and deal with the problem, many devices allow you to state when you’re trying to go to sleep rather than relaxing. And some offer options to manually correct any mistakes you think the device has made.

Comparing personal sleep trackers to polysomnography

Several research studies have highlighted the lack of research and evaluation of the accuracy of consumer sleep trackers. In fact, there’s very little research into any of them, so you’re left to make decisions based on the reviews and experiences of other people.

The only study I could find was conducted by Dr. Christopher Winter and published in the Huffington Post in 2014.

Dr. Winter wore a Fitbit Flex, Jawbone UP, Basis Chrome and Philips Spectrum Actiwatch whilst undergoing a Polysomnography in a sleep clinic.

It’s interesting to see how the 4 devices correlate with the PSG, with none of them being totally similar, as you’d expect. However, even more interesting is that all 4 of them give different readings.

While hesitant to draw too many conclusions, he does state that the Basis was the most similar to the PSG recording. Unfortunately, the Basis is now discontinued!

It’s unlikely that sleep clinics will be opening their doors to many people who want to do these kind of tests, so it’s interesting to see this rare piece of personal experimentation. The good news is that it does at least show that consumer products have the potential to be accurate.

Beyond actigraphy: the advancing technology in sleep trackers

To make matters even more complicated, in 2015 personal sleep trackers started to appear which promised to be even more advanced when it comes to sleep tracking.

One such device which claimed to lead the way is the Jawbone UP3. Jawbone claim that rather than measuring brainwaves – as happens in Polysomnography – instead they use a range of physical sensors to identify REM, deep and light sleep.

So in addition to actigraphy, they included other sensors such as bioimpedance, which measures heart rate. The idea is to use the measurements together with a complex algorithm to identify the physical characteristics of the different sleep stages.

Unfortunately, Jawbone has now been discontinued…

Fitbit’s new sleep tracking

photo of 3 sleep trackers on one arm

Fitbit leads the way in the wearable sleep tracking world, though they haven’t been without problems either. Historically, they received a fair bit of criticism over the accuracy of not just the sleep tracking, but the activity tracking too.

In 2017, they announced a big update to their sleep tracking, offering sleep stage tracking with the Charge 2, Blaze, Alta HR, and Ionic.

It seems that Fitbit now believe they have the technology to accurately calculate sleep stages, combining movement sensors with constant heart rate monitoring. And interestingly, they are making use of the colossal amount of data they now have, thanks to millions of users.

So now you don’t just get total sleep time and restless. You get total sleep time, time awake, light sleep, deep sleep and REM sleep. Then you can compare that with what the typical time in those stages is for people of your sex and age.

Could it be then that personal sleep trackers are now able to correctly identify your sleep stages and cycle in addition to just the total time you spend asleep?

For now it doesn’t appear that much research has been done into how accurately they can actually do this.

My current App data looks very realistic, and is measuring up well against my mental note-taking. But my personal opinion would still be to take all the latest claims with a small pinch of salt until they are proved accurate in independent tests.

Non-wearable bedroom sleep monitors

sleep tracker test featured imageDevices such as the BeautyRest, S+ by ResMed, Emfit QS, Sleepace Reston, Withings and Beddit take a very different approach.

These are dedicated non-wearable sleep trackers which are only used in the bedroom and don’t go where you do.

Although there are a couple of exceptions, the norm is to have a thin sensor which you lie across your bed or under your mattress and sleep on top of.

They each have different claims as to their accuracy, ranging from the Sleepace which says it has medical grade sensors to the Withings and Beddit measuring breathing and snoring.

Again, these devices haven’t undergone rigorous independent testing to my knowledge. However, they do seem to be an interesting alternative for people who don’t want to wear a tracker on the wrist while sleeping.

They make some bold claims as to being the most accurate sleep trackers. For now though, independent reviews by customers, technology review websites and myself have found that, like wearable devices, they have their own unique pros and cons.

I think they can definitely provide some very useful information about your sleep, especially if you sleep alone so your partner won’t lie on top of your sensor by accident. But whether they are a better option for you than a wearable device is very much a personal choice.

You can find out more about some of these devices in my extended review of sleep trackers.


It’s particularly tricky to assess how reliable personal sleep trackers are, and even the question of how they work has more than one answer.

Many of them rely heavily on movement sensors, which has been shown in scientific research to be accurate for measuring factors such as the total time spent asleep.

However, what’s still not clear is how accurate personal sleep trackers are compared to the medical grade devices used in those research studies. There just hasn’t been much independent scientific research to test all of the devices you can buy yourself.

In addition, wearable technology is a rapidly advancing market, with new devices and new promises of accuracy appearing all the time.

Even if researchers decided to put a range to the test, by the time they published the results, a new range will already be in the pipeline.

So for now, my advice would be to try to have realistic expectations of what you can get from your sleep tracker. They are definitely a useful tool for giving you an overview of your sleep. But do be aware that they aren’t perfect yet, and may make mistakes from time to time.

And that doesn’t necessarily mean they aren’t good, rather that it’s still a developing technology. It will be very interesting to see just how accurate they do get in the coming years.

For now though, if you want an insight into your sleep, they will certainly give you that. But above all, if you do suspect you have serious problems with your sleep, do remember to speak to your doctor about it.

At the end of the day, they and the sleep specialists they can refer you to are still the most reliable way to find out about your sleep and diagnose any sleep disorders.

My recent test of the accuracy of different trackers

In 2018, I tested 3 different sleep trackers at the same time, comparing them to my manual sleep diary. It’s still not the most objective test, but the results are interesting nonetheless.

Your views

What do you hope to find out from using a sleep tracker? Which device have you tried before, and did you find it to be accurate, or provide you with useful information?

48 thoughts on “How Do Sleep Trackers Work And Are They Reliable?”

  1. Excellent article, thank you. I have been monitoring my sleep lately with a Fitbit Alta HR, since I recently had a knee replacement. And like the first one 20 months ago, my sleep is seriously disturbed by the discomfort. I had a couple of full sleep studies as I have sleep apnea, and I think I am pretty self-aware of my sleep situation. So far I think the Alta HR is approximating my sleep reality pretty accurately and I am focused on getting more deep sleep and less light sleep. The feedback helps me to take steps to create best sleep conditions possible and its way better than Finding a night in a sterile sleep lab with guck in my hair and wires taped all over :-)

    1. Hi Liz
      You’re welcome! It’s nice to hear you’re happy with your sleep tracker. I think it’s important to create the best conditions possible for sleep, no matter what a sleep tracker says – and especially if you have a diagnosed sleep disorder. I always make as much effort as possible to ensure my bedroom is just right for sleep – recently I think I’ve become even more convinced that the temperature is the most important factor for me – so I always pay particular attention to that, even preparing the bedroom well in advance to ensure it’s the best temp. when I go to sleep rather than getting into bed and then deciding if it’s too hot or cold and then waiting for my efforts to change the temp. to take effect.

  2. Hashem ElAssad

    Hi.. so I have both insomnia and hypersomnia (it takes me alot of time to sleep. Once I sleep, I sleep a lot and during the day, I’m frequently drowsy and I frequently nap). Any recommendations for a sleep tracker (probably on the wrist) that would record my nodding off(s)?

    1. Hi Hashem
      The problem is that sleep trackers usually don’t start recording sleep until a set time has passed – an hour for example. So if you nod of for 5-20 minutes, they will probably not record sleep. This is to stop them accidentally mistaking for quietly resting, reading, watching TV etc as sleep. You would need to check carefully the different devices to see what recording options they have. But all the ones I’ve tried so far don’t have a short nap recording function.

  3. Thanks for this great article!

    Some years ago, I’ve been using the Sleep Cycle app on my iPhone (when you still had to place it on your bed) for a while and just recently re-downloaded it to use with my watch. What I’m most curious about, and what I can’t really find anything on: How does any accelerometer-based sleep tracker identify between SWS and REM? Sleep Cycle doesn’t provide information on time spent in REM sleep, but I’ve seen other apps that claim to do this. During both SWS and REM the body is as good as motion-less (completely relaxed during SWS, actually paralyzed during REM). You mention there has been some science to show that generally accelerometers are a good indicator to track sleep, but this keeps puzzling me. I’m wondering this because if, for example, a person spends a lot of time in REM but actually lacks SWS, this would give false positives as the wearable would pick it up as “deep sleep” due to a lack of movement? Obviously, any wearable can only give an indication of sleep quality past the total duration of spending in bed and maybe waking up during the night, but I’m really curious as to whether or not these two phases can actually be differentiated just by movement alone

    1. Hi Anke
      Thanks for your comment. I think that’s a good question, and I personally don’t think any personal sleep tracker can be relied on to provide completely accurate breakdowns of sleep stages based on movement alone. I think including heart rate monitoring helps, as it provides another measurement beyond simply movement.
      But until respected sleep experts publish a definitive study of wearables or non-wearable sleep trackers in a lab, compared with a polysomnogram, and announce in a scientific journal that ‘we can now trust these devices’, it’s probably best to take the readings with a pinch of salt still.

      1. I have to wonder if perhaps another data point that could be useful to incorporate with the accelerometer and heart rate data may potentially be a skin contact thermistor. How useful this might be would certainly require some research especially since the wrist could only give a rough approximation of core temperature and the diurnal variation in core temp is rather small at best. Still potentially with some clever algorithm and in concert with other data points it could perhaps be potentially useful at least given the practical limitations of externally wearable technology for constant wear.

        In an ideal world having health sensors in key areas thoughout the body would give the best results but people naturally are not likely to be comfortable wearing a massive wiring loom and sensors all over externally so short of moving to implantable sensors it’s probably the closest we could get for now doing what can be done with a simple relatively unintrusive external device.

        1. Hi Matt
          Thanks for your comment. It’s an interesting proposition – I wonder if any of the tech companies are working on something like this for the future. What’s clear is that better measuring tools are needed, whether it’s a worn or contactless sleep tracker. I hope the puzzle is cracked before too long, but without resorting to too many wires, as I agree – that wouldn’t exactly be appealing to many people.

  4. I have recently bought a fitness tracker wristband made in China using H-band App and bluetooth communication with my smartphone.
    The tracker measures the usual movements also Heart Beat Rate and Blood Pressure with LED light technic. I do not know if the sleep tracking funtion use those functions. I can see some accuracy in the sleep result presented but also some discrepances especially when staying in bed or even going up and sit watching television and eating breakfast. The sleep tracking starts automatical after 10 pm up to 8 am. I have understand that to end the sleeping period I have to do more movement than just going up from the bed to the toilet and then sit rather still or go back to the bed but not to go on sleeping.
    I know that I snore a lot but that is of course not shown in the sleep result quality. I normally get lot of deep sleep time especially in the last hours of my sleeping period. With the smartphone included in the sleep tracking system a registering of the snoring sound sleeping alone could be of interest I think.

    1. Hi Gunnar
      Thanks for your comment. I agree that moving a bit more can help to tell the tracker that you’re awake now. If you do go back to bed and relax, even just moving your arm from time to time might help. But it’s a shame they often mistake relaxing for sleep. As for snoring, there are a couple of that do that. You can also get phone Apps that will listen out for snoring.

  5. I’m using the BeautyRest SleepTracker (yes, it’s the mattress people). It costs about $70 and comes with two under-the-mattress sensors, although I use only one. Every morning, about 30 minutes after I get up, there’s a report in my email inbox. The graphics are stunning and I view the reports on my iMac, full screen, which is much more satisfying than on a phone. I bought it to record my trips to the bathroom and it nails them very accurately. So far as I can tell, its heart rate and breathing rate numbers have no connection with reality, but their graph lines do show gaps at the right times.

    1. Hi Charles
      Thanks for your comment. I’m actually in the middle of writing a long article detailing a test I did where I used the Beautyrest tracker, Emfit and Fitbit Versa for a few days at the same time. I was quite impressed with the Beautyrest. Like you say, it’s good at spotting wakings, and the graphics and fantastic. I’m not so sure about some of the finer points like sleep stages, but it observable seems to do the basics pretty well.

  6. Thanks for researches and efforts, the article was illustrative.
    I am a 58y old female with serious insomnia issues, sometimes not sleep at all during the night. 2 weeks ago I bought some cheep no-name bracelet, for running purposes actually, but found myself very surprised on how accurate it traces my sleeping phases. Of course I can’t control the difference between deep and light sleep to be compared with the device reports, but awaken phases in between are spotted perfectly.
    Moreover, I am experiencing better sleeping with the bracelet for a funny fact – that I am taking my sleeping issues more seriously because of data tracking and put myself to bed when needed (at the evening instead of previously at the mornings or not at all). Good start I think :), so I am greeting very much a fast development on this kind of toys.

    1. Hi Mg
      Thanks for your comment. Although I always say to take the sleep stage data with a pinch of salt, it’s good that you feel it’s getting the timings you can check yourself right.
      And if it’s encouraging you to take steps to improve your sleep, that’s a good result!

  7. I have been diagnosed with narcolepsy and take medication twice daily to stay awake. I just started using an app on my iphone6 called Sleep Cycle to track my “deep” sleep which is a deficit in narcolepsy. Each night the sleep data is recorded as a graph and it very interesting to see the variety of waking & “deep sleep” cycles. The research shows that movement is the indicator for “deep sleep” in all the sleep trackers. That being said, I am using Sleep Cycle to track my sleep patterns and keep me honest as to my actual bedtime schedule!
    Thanks for the info on your blog,

    1. Hi Keynsham
      Thanks for your comment. I know Sleep Cycle is a popular App. Just to correct something you said though – some sleep trackers also use heart rate to help determine which sleep stage you are in. But really, none of them can be completely relied on to accurately track sleep stages still – though they are getting better I think.

  8. I use the Fitbit Charge 2 and I find it very “hit and miss” regarding sleep tracking. I am recording my findings in the blog – some nights it seems spot-on, and on others COMPLETELY WRONG. I don’t believe that home technology is yet anywhere near the accuracy of an EEG, so sleep tracking on even the most expensive devices currently available is at best only a rough guide. I believe that the means to accurately measure your sleep at home is at least a decade or so away.

    1. Hi Gary
      Thanks for your comment. You’re right in that home devices still need to be taken with a pinch of salt, and can’t compare to an EEG. Having said that, I’ve found both the Ionic and Alta HR to be more accurate than the Charge 2.
      Good luck with your blog!

  9. Have you reviewed the Oura ring? It sounds promising and I wonder how it compares to the Fitbit solutions in terms of accuracy.

  10. For several months I have been using the Fitbit Charge 2 which says I am not getting enough deep or REM sleep. I started using the ResMed S+ to compare results. Huge difference! S+ said I am getting 2 hours deep sleep and Fitbit says 38 minutes of deep sleep. Do you know why the difference and which would be more accurate?

    1. Hi Jill
      Thanks for your comment and interesting question. It’s not as straightforward as saying one is the right amount and the other not, unfortunately. One major factor is your total sleep time. But unless you’re sleeping for a really long time, that 2 hours sounds like a lot to me. Then again, the 38 mins could be an underestimate if you’re getting a good night’s sleep. But really, considering the inaccuracies that crop up with sleep trackers, you might find the truth is somewhere in the middle! What does your fitbit tell you when you look at the benchmarking with other people your age?

  11. Thank you. This is a much needed article. Sleep Apps for wearables are in danger of over promising. In my experience they don’t clearly set out how they work and their limitations.

    I use an Apple Watch App called Pillow, have you reviewed this?

    1. Hi Dan
      Thanks for your comment, and I’m glad you liked the article. Yes, it’s a shame really that they aren’t so reliable! I have plans in the pipeline to do a huge test of lots of different ones all at the same time. I’d love to take the test into a sleep lab to compare them with their equipment, though it might not be possible. If I do manage to get round to this kind of test, I’ll be sure to write about it!
      And no, I haven’t used that App – can you tell me a bit about it?

  12. Hi, thanks very much for your comprehensive and sensible explanation of how sleep trackers work and comparing different devides. I’m 65, female, and over the past couple of years my sleep has been getting less restful. So a few months ago I bought a Fitbit One. Though the accuracy is questionable, comparing its results over many weeks gives me a general sense of how I sleep each night and is actually quite reassuring. It does confuse sleep with awake-still, but the latter state can be restorative too. I’m looking for a device now that checks more factors than just activity and will give a more defined readout. Your articles have been very helpful in choosing which one to purchase. Thank you.

    1. Hi Sharon
      Thanks for your comment. I’m glad you found the article helpful – thanks for saying so! The Fitbit One is definitely at the lowed end of the market in terms of what you can get from it, and you’re right in that the sleep readings can be questionable, but over time give a general idea. Hopefully you’ll get some more interesting data with your next choice of sleep tracker.

  13. I am just wondering if it is also meaningful to have a sleep tracker for baby? Is it meaningful to consider to improve the baby’s sleeping quality – as it sounds babies are always sleeping no matter what environment they are in. But if there is a sleep tracker for them, maybe their emotion can be understood better for “day time” as they cannot “speak” out what they need. If there is some ways to improve their sleeping quality, will it be helped their brain development?
    I believe it is not necessary for the tracker to wrapped around the wrist but anywhere in the body, just for the wrist, the movement is the “most obvious”.

    1. Hi Linda
      Thanks for your comment. To be honest, I’ve never heard of anyone using a sleep tracker for a baby. I think the way they are calibrated, you’re likely to get lots of warnings about sleeping badly because of waking up too often and then sleeping for too many hours during the day, so I can’t see that it would be helpful.
      Having said that, there are loads of Apps for babies which take into account things like sleep and sleep patterns. If you have a look online, you’ll find plenty of reviews of them that you could read through and see if any do what you’d like it to.

  14. Hello Ethan, I have RLS (Restless Leg Syndrome) and take drugs to help the symptoms but I never feel like a have a restful sleep, I wake up exhausted and tense. I don’t care about daytime activity monitoring, just my night time … dare I say “sleep” and what is happening during the night. Can you recommend a type of monitor that would be useful for this type of issue. Thinking to maybe use it to help adjust my medications with my doctor. Oh, also don’t want to spend tons of money either ;-).

    1. Hi Alden
      Thanks for your comment. Even though you’re not interested in activity tracking, you might find a wearable device helpful because they work mainly based on movement. So if you move around a lot in the night, they might pick up on that and record it as restless sleep or being awake. But then again, most of the bed based ones will also tell you if you moved around a lot in the night! So if money is also a factor, I’d go with one of the cheaper ones first and see if it gives you the results you’re interested in. What you’re asking for isn’t anything particularly unusual for sleep trackers, so you’ll find most of them will try to record how much you’re restless.

  15. I’m looking for a sleep monitor that will record my heart rate continuously. I have sleep apnea (I use a CPAP) and I want to see my HR on a graph because I know apneas cause a slower HR and then a higher HR afterward. My DreamMapper app doesn’t give me a graph just the number of apneas per night. Sleep stages would be nice, too

    1. Hi Alice
      Thanks for your comment. Many wearable sleep trackers give you your heart rate readings these days. But are you looking for one that will track apneas and correlate it with your heart rate? If so, I’m not aware of one that does that.

    2. Suggest you try an inexpensive recording finger pulse oximeter. When you download the data in the morning, you’ll get O2 desat and heart rate tracings thru the night. The CMS 50D+ goes for less than $40.

  16. Hello, I took a sleep test and was diagnosed with moderate sleep apnea. After trying different solutions I settled on a customized mouthpiece built by my dentist to increase air throughput. I then went back to take the sleep test with my mouthpiece and the result was I don’t have sleep apnea when wearing the mouthpiece. Although it is night and day compared when I wear the mouthpiece vs not wearing it, I also notice some days are even better than others when wearing the mouthpiece. Which device would you recommend that provides more accuracy for REM and deep sleep per night?

    1. Hi Dion
      Thanks for your comment. It’s great that you had such good results with the mouthpiece! To be honest, I don’t think any of them are 100% reliable when it comes to breaking down the sleep stages. However, I’d probably recommend one of the stand alone devices over a wearable one. Have a look at the different ones and see which you like the sound of based on the other features it offers too.

      1. Headband Dreem 2 claims accuracy of sleep stages: 75%

        Garmin recently published an overall accuracy of: 69.7%

  17. I am 72, in good shape, still working, doing sports and other activities. At about 10pm I am tired and wish to sleep. As soon as in bed, my tiredness gone and I waste time in bed untill 2am and sometimes even longer. When asleep. I sleep rather well until about 8am. Could you recommend devise which would improve my sleeping habits?

    1. Hi Dov
      Thanks for your comment. Many devices will encourage you to stick to sleep goals that you set yourself. So you can say what time you’d like to go to sleep and wake up, and they will give some kind of positive or negative feedback if you get within a target range of that. Fitbits have that option for example, but others do too.
      To be honest though, the best way to improve your sleep habits is by planning them yourself. It may be that in your case, you’re feeling tired but not ready to sleep. I’d have a look at my article about fixing your sleep schedule where I explain more about that.

  18. My husband was given a Fitbit Flex & we both tried it for sleep monitoring. It didn’t work well (and was very inaccurate at measuring steps & activity, too, but that’s a separate problem).. I especially remember that the Flex said I woke up 46 times in one night… what actually happened that night is that I slept little, and only in 2 or 3 spells. I wish something was a decent monitor, although what I really want is just to sleep better over all. Nothing works, argh.

    1. Hi Julii
      Thanks for your comment. I had a Fitbit Flex some time ago, and remember being less than impressed by the general accuracy. Having said that, I’ve found other Fitbits more accurate, namely the Charge 2 and Surge.
      But yes, it’s unfortunately the case that sleep trackers get confused between awake and still or asleep. So if you’re awake and still a lot, trying to sleep, but then inevitably toss and turn frequently, it might think you were asleep and keep waking up. That’s why I think sometimes when you have a particularly bad night, it’s good to correct the information manually the next day on the App. Though of course, in an ideal world you’d never need to do that because it would be totally accurate! Have you tried any of the other bed-based trackers, like the Withings Aura, Beddit or Sleepace, or perhaps even the S+ by Resmed? It might be worth trying one of those to see if it’s more accurate for you.
      As you say, the main thing though is to sleep better overall. And for that, there’s plenty of advice around this website. If you haven’t already taken a look, I highly recommend having a look at the sleep hygiene section, where I’ve tried to compile as many good ideas for better sleep as I could.

  19. In a very short test period, I have noticed that my wrist monitor only seems to tell me I have been in Deep Sleep at times when my wife is not in the bed alongside me.

    Does having a partner in bed with you affect the results if they are restless during the night??

    1. Hi Alan
      Thanks for your comment. It depends which sleep monitor you have, but it’s definitely possible. Which one are you using? I think more so with those that have measuring strips on the bed which your partner can touch with their body. Wearable trackers on the wrist I think are harder for a partner to disrupt. But just thinking off the top of my head, I wonder if a partner is very restless, perhaps it could make you more restless if you’re a light sleeper? I have no evidence for that idea though – I’m literally thinking out loud here.

  20. I am searching for a device to monitor my sleep. Like susan I have narcolepsy but I’m not sure that’s relevant. I feel like there’s a lot of moment where I am awake in the middle of the night and I would like to monitor it in order to give like a sleep diary to my slepcialist. I think the Jawbone UP3 could do that. I could use only at night (seems that the bracelet is not lasting long…). I found on other device the ability to add hashtag to the day to see what factors could improve or damage sleep quality. I’d like to have that but I’m not sure the UP3 does that. Anyhow, it happens also often that I fell asleep while I didn’t plan to do so and start my night too early, often I wake up to put my night cloths as others people would do to pee but I have no idea how long I’ve been sleeping, what does it do to my sleep cycles, etc. I could do a basic diary with a pencil and everything but I know I woul forget at some point to do it.

    1. Hi Sabine
      Thanks for your comment. I think the main thing for you then would be one which records sleep automatically, rather than having to tell it yourself that you’re going to bed now. The UP3 will do that. And then one which is particularly good at recording nighttime wakings. Again the UP3 will do that, but then so will many others. The good thing about the UP3 is that it’s very inexpensive compared to many others. So if you want to try one, but don’t want to spend too much, it’s a good choice. However, if you want to get a really detailed view and aren’t interested in activity monitoring during the day, you could perhaps try one of the bed based ones such as the withings aura or beddit.

  21. My intention is to measure ‘how much’ I sleep rather than ‘the quality’ of my sleep. Meaning assessing depression not insomnia. I currently use the leaf and love it except it only tracks sleep for a defined period, not 24 hrs: 9PM – appears to be 10 AM. To credit the Leaf you have the ability to add naps but I would prefer to not do so everyday.
    So I’m looking at google apps that would allow me to turn it on and off, on and off with nap, on and off with nap, on sleep….. I’m sure there’s something but I feel the market is more geared to insomnia. I’ve a sleep test but it wont definitively track time.

    1. Hi Amy
      Thanks for your comment. Many, if not most, sleep trackers allow you to manually input the time you went to sleep and woke up, if that’s what you mean? But if you want one which is constantly on and automatically monitors your sleep 24 hours a day, you can get that also.

  22. Suzanne Miller

    I have been using the Fitbit Flex to monitor sleep . I have narcolepsy and and am on Adderal for daytime sleepiness . Have had a sleep study to confirm . I usually wake at 9 00 and go to bed at 11 30 . My age 68 yrs . I sleep about 5 to 6 hrs , according to Fitbit .. I feel exhausted after waking up until 12 00 or so and then have about 7 hrs of fairly productive time . I guess Fitbit must be right. I wish I did not have to spend so much time in bed to get so few hrs of sleep.

    1. Hi Suzanne
      Thanks for your comment. It’s interesting that the Fitbit is reflecting what you think is the case with your sleep – that’s a good thing! Yes, it can be frustrating to be in bed and not sleeping. Have you spoken to a sleep specialist about your sleep schedule? Perhaps they can suggest a routine for you that isn’t so frustrating. It’s in fact very normal to sleep for less hours as we get older. Have a look at this article about how much sleep we need. Sometimes it can be helpful to know that actually we’re getting enough sleep, as often the worry about not sleeping enough makes us feel worse.

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