Sleep trackers can help you measure your sleep objectively so that you can take steps to improve it. Some even offer detailed insights into factors that may be negatively influencing your sleep, such as your environment, diet and lifestyle.
This article lists the best sleep trackers based on scientific research and validation studies, their underlying technology (such as number of sensors and sampling frequency), and my personal experience using each device.
My picks for the best sleep trackers are:
- Best overall: WHOOP Strap
- Easiest to wear: Oura Ring
- Best for snorers: Biostrap Evo
- Most accurate: Muse S
- Best non-wearable: Pod 3 by Eight Sleep
I’ve also included a list of sleep trackers I don’t recommend (including one popular option from Fitbit) due to inaccurate data, a lack of reliability, or the absence of key features that are necessary for extracting useful data from the device.
The Five Best Sleep Trackers
Best Overall Sleep Tracker: WHOOP Strap
- Multiple sensors, paired with an advanced machine learning algorithm.
- Developed by data scientists and validated with pro athletes.
- Slick design and comfortable to wear 24/7.
- Actionable data that improves your health and well-being.
- Five-day battery life.
- Requires a monthly subscription.
In addition to being the best overall fitness tracking device on the market today, the WHOOP strap is also the most advanced and most reliable wrist-worn sleep tracker, thanks to the inclusion of four different sensors that sample data 100 times per second.
These sensors include:
- Optical heart rate sensor with pulse oximetry capability, which improves the capture of heart rate data during sleep.
- A 3D gyroscope to detect movement and respiratory rate. Both of these biometrics can be used to identify sleep stages. For example, you normally don’t move during deep sleep and your respiratory rate is lower than during REM or light sleep.
- Skin conductance to detect changes in electrodermal activity, which changes when you fall asleep or when you’re stressed.
- Ambient temperature monitor to detect changes in skin temperature. Your skin temperature drops when you fall asleep and changes throughout the night, based on your sleep cycle.
Combined with a machine learning algorithm that constantly learns from the anonymous data provided by other WHOOP users, these sensors make for an extremely powerful device that is able to provide you with accurate data and actionable insights for improving your sleep.
WHOOP also helps you correlate your lifestyle choices (such as alcohol consumption, meal timing and workout intensity) with changes to your sleep quality, features a sleep coach that recommends the ideal bed and wake time for optimal sleep performance based on your individual data and health metrics, and has a smart alarm that can wake you up silently using gentle vibrations.
You can learn more about these features and how they work in the sleep tracking section of my in-depth WHOOP review.
If you’d like to give WHOOP a try, you can use the link above to get a free month added to your subscription.
Easiest Sleep Tracker to Wear: Oura Ring
- Combination of sensors.
- High sampling data.
- Long battery life.
- Comfortable to wear.
- Doesn’t track skin conductance.
- Lack of validation studies.
The Oura Ring is packed with advanced sensors for measuring heart rate, body temperature, heart rate variability and movement 250 times per second.
Most wearable sleep trackers are designed to be worn on the wrist, which can be inconvenient if you’re someone who regularly wears a watch or wrist-worn jewelry. The Oura Ring is an appealing option for these use cases, thanks to its very small form factor.
Until recently, one knock against the Oura Ring was a lack of validation from studies involving real-world data from a combination of regular users and elite athletes. However, in late 2022, Oura released a new sleep tracking algorithm that was validated against polysomnography (PSG), which is considered the gold standard of sleep tracking. Based on the studies Oura conducted, the algorithm achieved a 79% agreement with PSG. That’s relatively good, though it still puts Oura behind WHOOP as far as accuracy is concerned.
As of this writing, Oura’s new sleep staging algorithm is still in beta and hasn’t replaced the old algorithm yet entirely. In other words, the Oura app reports two sets of sleep data. Based on my testing, it appears that the old algorithm overestimates how much time I spend in REM and deep sleep, while the new algorithm slightly underestimates those figures.
The good news is that Oura is very consistent with its over-reporting and under-reporting. In other words, Oura is a great tool to keep tabs on how your sleep quality changes over time based on lifestyle interventions, even if the exact numbers you see are slightly inaccurate.
Additionally, the Oura app can send you a daily reminder when your ideal bedtime approaches, based on previous sleep sessions and your activity level during the day). This is valuable because one of the most impactful interventions to help improve your sleep is maintaining a consistent bedtime.
You can learn more in my in-depth WHOOP vs. Our Ring comparison article.
Best for Snorers: Biostrap Evo
- Monitors heart rate, HRV, O2 saturation and respiratory rate.
- Tracks your snoring levels.
- Some features are backed by validation studies.
- Was fairly accurate in my tests.
- Only samples data every two minutes.
- Without membership, the sampling rate is even lower.
Biostrap utilizes various biometric parameters to detect sleep, including heart rate, heart rate variability (HRV), oxygen saturation and respiratory rate. However, it doesn’t monitor skin conductance or temperature, and it only samples data every two minutes. If you choose to use the device without a monthly membership, the sampling frequency is even lower.
Unlike most of the sleep trackers I’ve tested, Biostrap can monitor your leg movements (if you purchase the optional “shoe pod” which comes with an adjustable ankle strap), and it can tell you if you’re snoring. I knew before using Biostrap that I had a habit of snoring after consuming alcohol, but the device helped me determine that I also tend to snore after consuming dairy. (That’s likely because dairy increases mucus production, which can tighten your nasal passages, thus increasing the likelihood of snoring.)
One downside to Biostrap is that you have to take the strap off for charging every morning, because the battery doesn’t last more than 10 hours if you turn on “Max Biometrics.” In comparison, WHOOP’s battery lasts for five days and can be charged by simply attaching the charging pack (without having to take off the strap).
It’s also worth noting that Biostrap doesn’t report REM sleep, because the company believes that there isn’t a way to accurately do so without the use of an EEG (see below). As a result, Biostrap lumps REM and light sleep together into a single metric.
Based on my testing, Biostrap appears to underestimate how much time I spend in the restorative phases of sleep (deep and REM sleep combined). However, as with the new Oura sleep staging algorithm, Biostrap underestimates restorative sleep very consistently. So even if the actual numbers show less deep and REM sleep than you’re actually getting, you can still use the device to detect changes over time.
Combined with the ability to monitor leg movement and snoring, I consider Biostrap a great tool to help track and improve your sleep.
It’s also worth noting that Biostrap offers comprehensive PDF reports you can share with your healthcare provider, and it even allows you to enable remote monitoring. For example, if your healthcare provider is part of the Biostrap community, they could monitor your sleep data remotely and fine-tune treatment plans on the fly (e.g., if you’re being treated for sleep apnea).
To learn more about how Biostrap compares to WHOOP, check out this in-depth review and comparison.
Most Accurate Sleep Tracker: Muse S
- Uses EEG technology to monitor brain waves.
- 10-hour battery life.
- Detailed sleep stage and sleep intensity reports.
- Validated accuracy based on several studies.
- Can also be used for meditation and biofeedback.
- Requires an active Bluetooth connection.
- Not as comfortable as a wrist-worn device.
Muse S is a brain-sensing headband that I’ve been using to get real-time feedback on my brain activity during meditation sessions. However, it’s also an incredibly accurate sleep tracker because it uses electroencephalography (EEG) technology — in combination with an optical heart rate sensor and a gyroscope — to monitor your brain waves in order to identify what stage of sleep you’re in.
Your brain waves change depending on sleep phase, so EEG is arguably the most accurate sleep tracking technology available.
In addition to reporting your total time asleep and the time you spend in the various stages of sleep, the Muse app records your sleep position and heart rate. All of this data is packaged up into a sleep quality score that gets reported every morning.
The biggest downside to Muse S is that it streams your sleep data to your phone via Bluetooth, instead of storing everything locally and then synchronizing it with the phone. This means you’re constantly exposed to Bluetooth radiation while sleeping.
Additionally, it’s worth noting that Muse S is not quite as comfortable as wrist-worn devices (or the Oura Ring). Don’t get me wrong: Muse S is as comfortable as a headband can be. But I generally prefer having a device strapped to my wrist rather than my head.
If you want to give Muse S a try, you can use the link below. Make sure you use code MKUMMER to get 10% off your purchase.
To learn more about Muse S and how I use it for both meditation and sleep tracking, check out my in-depth Muse S review.
Best Non-Wearable Sleep Tracker: Pod 3 by Eight Sleep
The only non-wearable sleep tracking device that I’ve found to be relatively accurate and reliable is Eight Sleep’s Pod 3, which is a temperature-controlled smart mattress that has a series of built-in sensors called “the Active Grid.”
I’ve been using the Pod to track my sleep for the past few years. Based on the comparison data I’ve collected, Eight Sleep’s tracking capability is more or less in line with the WHOOP strap.
Of course, the big advantage of the Eight Sleep Pod is that you don’t need to wear a tracker on your body. Additionally, Eight Sleep’s temperature control system gives you the tools to not only measure but actively improve your sleep.
Based on my testing, I’ve found that Eight Sleep is incredibly accurate at measuring heart rate, heart rate variability, sleep onset and sleep disturbances (i.e., wake-ups). It’s also fairly accurate at measuring deep and REM sleep, though I’ve seen some variance in that data when compared to WHOOP and the Oura Ring.
You can learn more about the Pod in my in-depth Eight Sleep review.
If you want to give the Pod a try, you can use the link below and get $300 off.
Sleep Trackers I Don’t Recommend
These devices might accurately track your heart rate, but I doubt — given their technological limitations — that they can reliably track your sleep (and your stages of sleep in particular).
I’ve listed these devices in alphabetical order:
Considering that the Apple Watch’s heart rate sensor and ECG feature are both FDA-approved, and are incredibly accurate according to third-party testing, you would expect the device’s sleep tracking to be at least fairly accurate.
Unfortunately, that’s not the case. The sleep data reported by my Apple Watch Ultra running watchOS 9 doesn’t match the data reported by my other (more technologically advanced) sleep trackers.
|Apple Watch Ultra||WHOOP 4.0|
For example, my Apple Health data from the past 30 days says that I spend an average of 0:39 in deep sleep and 1:34 in REM sleep. Just based on how I feel every morning (both physically and mentally), I think the Apple Watch underreports deep sleep.
I’m not sure if that’s because of the relatively slow HR sampling frequency (every few minutes), the lack of additional sensors, or something that I do (e.g., a lack of arm movement or my resting heart rate).
But I’m also aware of other users, such as this YouTube creator, who claim the Apple Watch has been reliable in tracking sleep and the various stages of sleep. So there is a chance that the Apple Watch works reliably for some but not all users.
If you’d like to learn more about the Apple Watch’s sleep tracking capabilities, you can check out my in-depth WHOOP vs Apple Watch article, which goes into more detail about the device’s sensors, how it attempts to track sleep, and other important details.
Beautyrest is a brand of the Simmons Bedding Company, which is a mattress manufacturer. While you could argue that they should know a lot about sleep, I frankly doubt they know much about the physiology of it, let alone the technology required to accurately track it.
My opinion aside, Beautyrest uses passive piezoelectric sensors (pressure sensors) under the mattress to detect even the smallest amount of pressure from movement.
Using those sensors, Beautyrest claims it can accurately monitor respiration and heart rate, light sleep, deep sleep and REM cycles, in addition to body movement and interruptions.
Sleeptracker® by Serta Simmons is clinically proven to monitor sleep patterns with an accuracy of over 90% for 90% of the population compared to medically operated professional polysomnography.Fullpower
The problem is that I couldn’t find any proof that the underlying technology is as accurate as Fullpower (the tech provider behind Sleeptracker) claims.
Fitbit offers a range of smartwatches and fitness straps that the company claims can accurately track sleep. Their flagship model is the Fitbit Sense, which offers sleep tracking via a combination of an optical heart rate tracker, a MEMS three-axis accelerometer, and a skin conductance sensor.
Considering that the Fitbit Sense has all the necessary sensors to offer relatively accurate sleep tracking capabilities, I was disappointed to discover that it fails to effectively leverage that technology.
In my tests, neither the total time asleep nor the sleep stages data was accurate and comparable to WHOOP and Eight Sleep (as I discussed in my Fitbit vs. WHOOP comparison article).
I’ve even heard some reports of the Fitbit Versa incorrectly recording HR data while it wasn’t even being worn.
If the software algorithm in the Fitbit Sense can’t even tell the difference between a real pulse and light reflected by a countertop (which may have been the case in the example linked above), I have no trust in its ability to distinguish between the various stages of sleep.
Withings Sleep is another under-the-mattress device that can supposedly track your overall sleep, sleep stages, respiratory rate, heart rate and snoring.
The idea behind this product is that your beating heart, breathing or snoring all cause different movement patterns that the sensor can pick up.
As I mentioned before, I’m skeptical of whether a $129 device can accurately pick up and correctly identify those patterns, especially if several of them happen concurrently.
What Sleep Trackers Measure
Automatic sleep detection can be accomplished using technology to record one or more of the following biometrics:
- Heart rate (including heart rate variability).
- Skin conductance.
- Skin temperature.
- Respiratory rate.
- Blood oxygen saturation.
- Brain waves.
It’s important to note that with the exception of brain waves (as measured by an EEG device, such as the Muse S headband), none of these parameters measure sleep directly. Rather, they can be used to estimate sleep based on what we know about how the body functions during sleep (and more specifically, during the various sleep stages).
Basic wearable sleep tracking devices monitor your wrist movement patterns to essentially guess if you’re sleeping (and in what stage of sleep you’re in).
Using only this approach is likely to produce inaccurate data. While a lack of movement can certainly be an indication of sleep, it’s an incredibly unreliable parameter.
For example, if you lie in bed watching TV before falling asleep, you might not move for an extended period, tricking this type of monitor into thinking that you’re asleep.
I experienced this type of false positive with various Apple Watch sleep monitoring apps. I even experienced such a false positive with the first-generation Biostrap.
In general, I recommend avoiding sleep trackers that only (or predominantly) depend on movement.
Heart Rate (HR)
An accurate heart rate reading, especially when combined with monitoring movement, can measurably improve the reliability of sleep trackers. That’s because your heart rate changes throughout the various stages of sleep. For example, during deep sleep your resting heart rate is typically at its lowest.
Unfortunately, getting an accurate heart rate reading is more difficult than you might imagine. That’s a big problem because a discrepancy of 10-20 beats per minute can dramatically skew the sleep data.
You can skip ahead in this article to learn more about how sleep trackers collect HR data.
Skin conductance is a term that describes the electrical characteristics of the skin. In other words, the amount of electricity that can pass through the skin varies, based on different factors.
The interesting thing is that skin conductance changes based on the stage of sleep you’re in. That’s why WHOOP has a built-in sensor that measures electrodermal activity to further improve the accuracy of sleep stage detection.
Ambient Skin Temperature
Your body’s core temperature fluctuates while you sleep. For example, “non-rapid eye movement (NREM) sleep episodes are accompanied by core and brain cooling.” As a result, sleep monitoring devices can keep tabs on your skin temperate to detect changes in your sleep cycle and, in particular, sleep onset. Both the WHOOP Strap 4.0 and the Oura Ring can monitor skin temperature.
Heart Rate Variability (HRV)
Heart rate variability or HRV is the difference in timing between heartbeats. For example, if your heart beats 60 times per minute, the timing between each beat varies by a few milliseconds.
The amount of variability is determined by the two (competing) parts of your nervous system: the sympathetic branch and the parasympathetic branch.
Studies have shown that when you sleep, your HRV is greater than it is during the day. That makes sense, because when you sleep, the parasympathetic nervous system takes over to take care of digestion and recovery.
Some sleep and fitness trackers — notably, the WHOOP strap, have incredibly accurate HRV monitoring capabilities, which can help improve the accuracy of sleep tracking and many other things.
On a side note, the data provided by my WHOOP strap has played a key role in helping me significantly improve my HRV.
A person’s respiratory rate doesn’t usually change much throughout the night. If you see sudden spikes, it’s usually a sign of illness or a respiratory problem.
Certain sleep trackers — including WHOOP, Biostrap and the Oura Ring — keep tabs on your respiratory rate to help you detect early signs of illness.
Respiratory rate can also be used as an indicator of when you fell asleep, because your breathing is likely to be slower while sleeping than when you’re awake.
Some contactless tracking technologies rely on radio frequency to monitor your respiratory rate.
I’ve never tested such devices, but I have gathered from other reviewers that they aren’t incredibly reliable.
Arguably the gold standard in sleep tracking is EEG, which monitors brain waves and detects the various stages of sleep. Studies have shown that EEG-based sleep tracking is 91% accurate, and that it can be further improved by being paired with wrist-worn devices that also collect the biometrics noted above.
Most EEG observation is conducted in sleep labs, and usually requires that you spend multiple nights sleeping in a specialized facility hooked up to various devices.
However, there are some consumer-grade EEG devices available that you can use at home. One example is Muse S, the brain-sensing headband that I mentioned above. You can read my hands-on Muse S review to learn more about the device.
Blood Oxygen Saturation (SpO2)
Measuring blood oxygen saturation (SpO2) while sleeping allows you to uncover any respiratory issues you might be suffering from. For example, a stuffy nose, allergies, snoring or sleep apnea might lead to lower-than-normal blood oxygen levels.
While most healthcare providers consider 95-100% a normal blood oxygen saturation, I often have levels of 93-95% overnight. At first, I was concerned about this. But then I learned that the higher your CO2 tolerance is (which is a sign of cardiorespiratory fitness), the lower your SpO2 levels often are. So if you’re a serious fitness enthusiast or someone who leverages intermittent hypoxic training, don’t be alarmed if your SpO2 levels are below 95% at night.
Of course, if they drop below 90%, I’d consult a healthcare professional to see if there might be an underlying issue you need to address.
How Sleep Trackers Measure Heart Rate
Most wrist-worn heart rate monitors use a technology called photoplethysmography to measure heart rate. That essentially means that they use LEDs to shine light through your skin; as blood pumps through your blood vessels, some of that light gets reflected. By measuring how much light gets reflected each time, an optical sensor can measure how often the heart beats.
Sleep tracking devices then use complex algorithms to convert that reflection data into a more or less accurate heart rate reading.
However, this raises the problem of “noise.” For example, if the optical HR sensor doesn’t have sufficiently-tight contact with the skin, ambient light can interfere with the reflecting light from the LEDs, thus reducing the overall signal quality.
On the other end of the spectrum, a sensor that fits too tightly might restrict blood flow and thus also reduce signal quality. Either way, the resulting heart rate reading could be inaccurate. And if the HR reading is inaccurate, the resulting sleep monitoring data will be inaccurate as well.
In my experience, most standard wrist straps (i.e., those that look like regular watch straps) don’t provide a good enough fit for the sensor to remain in constant contact with the skin. So it’s important to make sure that whatever sleep tracking you choose comes with a good strap that can be easily adjusted for a perfect fit.
The second factor that influences the accuracy of heart rate monitoring is the quality of the signal processing algorithm itself. Unfortunately, most brands don’t share much information about their algorithm (or the expertise of the engineers who designed it).
That’s why I’d recommend sticking with brands that either have a track record of developing advanced technology in the field, or that can back up their work with validation studies involving well-regarded data scientists.
Finally, one important factor that can influence the reliability and accuracy of any heart rate sensor is the frequency of the biometric data acquisition. The most accurate sleep trackers I’ve tested, such as the WHOOP, measure your heart rate (and other biometrics) 100 times per second or more. That’s important, because it allows them to immediately detect small changes in heart rate patterns.
Force and Pressure
Another technology that non-wearable trackers use to detect heart rate (and body movement) is force and pressure sensors.
I was highly skeptical of using a sensor under my mattress to detect my heart rate and sleep stages. For example, my experiments with Emfit QS (which is no longer in production) yielded highly inaccurate results. Plus, feedback from others suggests that such sensors often detect sleep when there is a lack of movement caused by inactivity, such as reading a book.
However, I’ve been using the Pod by Eight Sleep (a temperature-controlled smart mattress) and it’s got built-in pressure sensors to track sleep. Based on the data I’ve collected, Eight Sleep’s sleep tracking is fairly accurate and in line with what WHOOP, Biostrap and Muse S have reported.
What Sleep Trackers Do
Sleep tracking can mean different things depending on who you ask and what type of sleep monitor you use. In its most basic form, sleep tracking means measuring the time you’re asleep vs. the time you’re awake. This is often done by monitoring (wrist or full body) movement. The more reliable sleep tracking devices also keep tabs on your heart rate and other biometrics in an attempt to improve their accuracy.
The next stage of sleep monitoring includes detection and reporting on the four stages of sleep, which are:
- Awake time.
- Light sleep.
- Deep sleep (also known as slow-wave sleep).
- REM sleep.
It’s worth noting that detecting the different sleep phases is inherently more involved than simply differentiating between awake time and sleep time. As a result, you can expect a higher degree of unreliability among most sleep trackers when it comes to phase reporting.
Wake After Sleep Onset (WASO)
One often overlooked but important marker of sleep quality is wake time after sleep onset (or WASO). It measures how much time you spend awake after having fallen asleep and before you fully wake up. You can calculate WASO using the following formula:
WASO = Time In Bed - Total Sleep Time - Sleep Onset Latency
There are certain conditions that can cause a high WASO, such as sleep apnea, stress, hormone imbalance or a disrupted circadian rhythm.
Depending on your age, a WASO of 30 to 45 minutes seems to be ideal. From experience, I can tell that consuming too few carbohydrates increases my chances of waking up in the middle of the night to use the bathroom, thus increasing my WASO.
Most of the sleep monitors I recommend in this article measure WASO, but some use different terms for it. For example, WHOOP tracks your time awake and uses that to calculate your sleep efficiency, which expresses the percentage of time you spent asleep in comparison to the total amount of time you spent in bed.
Most of the advanced sleep trackers mentioned below also offer sleep coaching to help you improve the quality and consistency of your sleep by recommending the time you should go to bed and wake up based on your sleep goals.
Many of the apps that come with these sleep trackers also visualize sleep trends so you can identify how certain lifestyle choices impact your sleep. For example, WHOOP offers a journal you can use to answer a few questions each morning so that the app can correlate those answers with changes in your sleep quality.
How Sleep Trackers Can Improve Your Sleep
Many people use sleep tracking devices because they want to improve their sleep habits or sleep patterns by sleeping longer, falling asleep quicker, getting more restorative sleep (aka sleeping better), waking up less, or a combination of those goals.
Below are six common sleep parameters that you can directly or indirectly influence in order to improve your overall sleep quality and efficiency:
- Total time in bed.
- Total sleep.
- Sleep latency (how long it takes you to fall asleep).
- Sleep consistency.
- Time spent in restorative stages of sleep (deep and REM).
- Wake time after sleep onset (WASO).
Before you try making adjustments to any of these six parameters, it’s important to establish a baseline using a reliable sleep tracker. Only then can you judge the extent to which certain lifestyle changes positively or negatively influence your sleep.
For example, I’ve noticed that I get more consistent deep and REM sleep if I go to bed at approximately the same time every day. That’s called sleep consistency. I’ve also noticed that drinking alcohol before bedtime makes me fall asleep quicker, but I don’t get as much deep sleep as when I don’t drink.
You can learn more about that and all the other factors that influence sleep in this article.
Factors That Affect Sleep Tracker Accuracy
Most of the sleep trackers that I’ve tested or researched are inherently inaccurate for one or more of the following reasons:
- Reliance on only one or two biometric sources of information (i.e., movement or heart rate).
- Infrequent sampling of data.
- Inadequate algorithm (for processing the data).
- Issues with capturing biometric data due to lack of contact with the skin (i.e., a strap that’s too loose).
Confirming the accuracy of any sleep tracker is difficult, unless you compare it head-to-head with an EEG (which is what I’ve done for my Muse S review).
Fortunately, the company behind my favorite sleep tracker (WHOOP) has done exactly that. That’s one of the reasons why I trust WHOOP’s data more than that of any other wrist-worn device.
If your sleep tracker of choice doesn’t have any validation studies, here are some factors that can help you determine how accurate (or not) the device might be.
Sensors and Biometric Input
The fewer sources of biometric data your sleep tracker captures, the less accurate it will be. As such, I would categorically avoid any tracking device that relies only on an accelerometer to detect movement (because movement alone is not a reliable predictor of sleep).
Devices that combine an accelerometer with a heart rate sensor are much better. However, there’s a significant difference between sensors that capture the heart rate once every five minutes vs. 100 times per second. The higher the sampling frequency, the easier it is to detect changes in heart rate that might indicate a change of sleep stage.
My advice is to use a sleep tracker that leverages as many different input sources as possible.
The signal processing algorithm plays a major role in the quality of the results. That’s true in particular when the sampling conditions are less than perfect, such as when the sensor doesn’t have sufficient contact with the skin due to a loose strap.
It’s also important that the algorithm doesn’t fill gaps in the captured data with “guesses” just so that it can “complete the picture.” That means if the sensor can’t capture good enough data, it should discard it instead of guessing what the data (such as heart rate) might have been, based on readings before and after the gap.
Companies like WHOOP have entire data science teams that leverage machine learning combined with huge datasets from professional athletes and fitness enthusiasts to fine-tune their algorithms. That makes a huge difference in the quality of the reported sleep tracking data.
Type of Strap
The better the contact the sensor has with the skin, the better signal it will receive. Poor signal quality means more reliance on the sleep tracker’s algorithm, which often results in a less reliable heart rate measurement and sleep tracking.
The strap around your wrist should be tight enough to prevent both the sensor from moving and ambient light from reaching the sensor. However, it shouldn’t be so tight that the pressure limits blood flow in your skin.
As a general rule, it should be difficult to get your pinky finger between the strap and your wrist.
Most straps that I’ve tried in the past are difficult to correctly adjust for a perfect fit — especially traditional watch-like straps, which often produce either a much too loose or much too tight fit.
That’s why I like endlessly-adjustable straps like the Apple Sport Loop or the WHOOP’s ProKnit.
Frequently Asked Questions
Most of the sleep trackers on the market are gimmicks that don’t contain the sensors required to accurately detect sleep (and, in particular, the various stages of sleep). To get accurate data, make sure to choose a sleep tracker that combines the input from multiple sensors and that has been validated in independent studies. Examples of this include the Whoop Strap (my pick for the best overall sleep tracker), the Biostrap and the Oura Ring.
Some devices, such as the WHOOP Strap and the Muse S headband, have been shown in lab tests to reliably measure how much time you spend in each of the four sleep stages. However, most other devices fail miserably in that regard, leaving their wearers with incorrect and misleading data.
Some sleep trackers (including Biostrap) can assist in detecting sleep apnea and restless leg syndrome by monitoring your respiratory rate and leg movement.
Sleep tracking apps that don’t leverage dedicated hardware are utterly unreliable. Accurately detecting when someone is asleep requires a combination of hardware sensors that collect key biometric data (such as skin temperature, heart rate, etc.). An app by itself can’t do the job. Even the sleep tracking apps that rely on devices (such as those that leverage the Apple Watch) have proven (in my tests) to be relatively useless due to their respective hardware limitations.
Best Sleep Trackers: Final Thoughts
Accurately tracking sleep is difficult, because most of the consumer-grade devices we have access to can’t measure brain waves, which are the only direct indication of sleep.
Instead, wearable and contactless sleep monitors have to use proxies like movement, heart rate, skin conductance, ambient temperature and respiratory rate to make an educated guess as to whether a person is truly sleeping or not.
Besides getting quality data from as many different biometric sensors as possible, it’s up to the underlying software algorithm to make sense of the data and report back to the user.
The algorithm is where I think most sleep trackers fall short. It takes validation studies and large amounts of data for algorithms to reliably predict if a subject is sleeping and in what stage of sleep the person is in.
Based on everything I’ve seen, there are only a handful of sleep trackers out there that have both the underlying technology and algorithm to accurately track and help you improve your sleep.
All the other trackers are gimmicks that might over-report or under-report your sleep, and are thus virtually useless if your goal is to introduce meaningful lifestyle changes that result in better health and performance.
What sleep trackers have you used, and what was your experience regarding their reliability and accuracy? Let me know by leaving a comment below!
Michael is a healthy living enthusiast and CrossFit athlete whose goal is to help people achieve optimal health by bridging the gap between ancestral living and the demands of modern society.