How do Sleep Trackers Work? Are They Accurate?10:15

Sleep trackers and the fitness trackers they are often paired with are really popular right now and only growing in popularity. Some people like them simply because they are fun, but they actually can provide a lot of really great data that you could use to help improve your overall health, both physical health and mental health.

However, while most people understand how step trackers or different fitness trackers work, they are a bit confused about how the sleep tracker works and whether or not it is accurate. In this article, you will find all the information you need to understand how sleep trackers work, whether or not they are accurate, and make an informed decision on what kind of sleep tracker you want to get.

How Do Sleep Trackers Work? How Does It Know If You Are Asleep?

How a sleep tracker works really depends on the specific brand and type you get, but there are a few main ways that sleep trackers track your sleep quality and quantity:

( 1 ) Accelerometers

An accelerometer is a small motion detector. In a sleep tracker, the accelerometer is measuring how much you are moving while you are sleeping and then estimating how much of the time you are actually asleep and the quality of your sleep. While accelerometers alone can provide you with semi-accurate information about how long/much you are sleeping, if you are wanting accurate data about sleep stages, you need a tracker with more than just an accelerometer.

( 2 ) Heart Rate and Respirations

The leading sleep trackers on the market give some sort of information on the stages of your sleep, and they do this by tracking your heart rate and your respiration rate. There is a lot of evidence that supports the idea that heart rate and respiration rate are closely tied with the stage of sleep you are in. Trackers with heart and respiration tracking are probably the most accurate sleep trackers.

( 3 ) Environmental

Sleep trackers that sit on your nightstand or operate through your phone use a microphone to pick up on any noise in the room while you sleep. The tracker is specifically looking for frequent movement which would imply that you are restless or awake. The microphone may also track things like respiration, snoring, and how often you get up throughout the night. Noise trackers tend to be the least accurate out of all three methods.

Are Sleep Trackers Accurate?

Sleep trackers vary a lot when it comes to accuracy. The more high-end sleep trackers that have been tested a lot tend to be relatively accurate, but there are others that are not that accurate. For instance, trackers that rely mostly on sound and movement rather than your pulse or breath tend to be significantly less accurate and do not always provide a very clear picture of how you are sleeping.

Are Fitbit Sleep Trackers Accurate?

Fitbit fitness and sleep trackers are some of the most popular trackers on the market. For sleep trackers specifically, the Fitbit Charge 4 is considered to be one of the best. However, are they really accurate?

Well, the gold standard for sleep tracking is the EEG (more information on that below), so when trying to determine accuracy, we have to look at how it compares to the EEG. In studies comparing the two, it has been discovered that the Fitbit does in fact have a relatively accurate sleep tracker. In the video above, Rob ter Horst (The Quantified Scientist) tracks the two for a full year.

It does appear to slightly overestimate the amount of time you are spending in deep sleep, but it is accurate enough to help you get a fairly clear picture of your sleep.

Common Sleep Tracking Features

There are a lot of different sleep trackers on the market today, most of which come in the form of a fitness watch that you wear around your wrist, though there are some that lay on your pillow or nightstand rather than actually on your body. Of course, features vary a decent amount between different trackers, but there are a few features you can expect:

( 1 ) Sleep Duration

Sleep duration is probably the most common feature that all sleep trackers have. Sleep duration just means that the tracker tells you when you first fall asleep and when you wake up again in the morning. While this information can be helpful, it does not really give you a full picture of how much rest you are actually getting.

( 2 ) Sleep Quality

Many trackers go beyond simple sleep duration and also track when you toss and turn or wake up during the night. Sleep quality trackers can help let you know when you are actually experiencing sleep vs rest. Having sleep quality in addition to sleep duration really gives you a fuller picture of how much you are sleeping, but you are still missing some key information.

( 3 ) Sleep Phases

If you want to understand how much you are sleeping and how restful that sleep actually is, you will want to get a tracker that also tells you how much time you spend in each sleep phase. This can get really specific, but it is often just divided into awake, light sleep, deep sleep, and REM sleep. Some trackers will allow you to set alarms using this feature so that it will wake you during light sleep rather than deep or REM sleep.

( 4 ) Environmental Factors

These features most commonly come in sleep trackers that lie on your nightstand or clip to the pillow because they rely more on sound and movement to track your sleep. Other trackers also track environmental factors such as light or temperature, which could help you figure out how different factors affect your sleep.

( 5 ) Lifestyle Factors

Some trackers have you record various different bits of information so you can figure out how different factors affect your sleep. Trackers may have you record things like caffeine, when you eat, what you eat, or your stress level.

Differences Between Sleep Trackers and EEG Devices

The EEG or electroencephalogram is a type of test that tracks the electrical activity in your brain while you sleep through small metal discs or electrodes that attach to your scalp. Your brain emits very specific types of brain waves during each sleep stage, so an EEG provides a very accurate record of you sleep.

If you were to go in to get a sleep study done at some sort of doctor’s office, they would use an EEG. They may also use heart rate monitors or respiration monitors to get other kinds of data, but the EEG is what they will use to really track your sleep. If you are looking for the accuracy of an EEG, but do not really want to go in for a sleep study, you can buy personal EEGs. Just know that they tend to be significantly more expensive than a fitness or sleep tracker.

On the other hand, as we have previously discussed, sleep trackers track a wide variety of different things to help make estimates on how much you are sleeping from movement to sound to heart rate. These different things have been scientifically linked to different sleep stages, but they are not nearly as precise as the brain wave monirotring of the EEG.

For instance, the Fitbit Charge 4 primarily uses heart rate to track your sleep. Heart rate has been proven to be linked to different sleep stages, but there is not an exact rate for each stage, therefore it is not 100% accurate.

Conclusion

So what does all this mean for you? Well, if you are concerned about your sleep or health issues related to your sleep (neck pain, stress, headaches, fatigue, etc.), buying a sleep tracker of some sort could be highly beneficial to you, but it is important that you make an informed decision when you do so.

You need to consider how much information you are looking to track (sleep duration, sleep quality, sleep stages, etc.) along with what kind of monitor you want. A monitor that tracks heart rate and respiratory rate will most likely be the most accurate, but it also could be the most expensive.

It is also important to note that while you can use a sleep tracker to identify potential problems if you are concerned about any real sleep disorders, it is important that you see a doctor and get a professional sleep test done.

However, for day-to-day life and health, a good sleep tracker is all you really need. Once you have information about your sleep you will better be able to understand and make decisions regarding your health. For instance, some people consider sleeping without a pillow due to certain health benefits, and having a sleep tracker can actually help you see if your sleep does improve without a pillow versus with a pillow.

If you keep track of other factors like caffeine, stress, and meditation, you can also figure out which of those factors help and hinder your sleep health. A sleep tracker really does provide lots of great information that can help you improve your health, but it is up to you to do the work.

Want more insight on getting better sleep? Read the articles below.