How Accurate Is The Fitbit Sleep Tracker?

The Fitbit Sleep Tracker was released in 2017 and was received with arms open wide by consumers and a bit of skepticism in the world of medicine. Right now though, questions are arising about the accuracy of the gadget and consumers what to know “just how accurate is the Fitbit sleep tracker?”

We open with this comment from the Fitbit community by Leyla1. 

According to her, she had a great sleep one night, hardly moved, and hardly dreamed. However, the tracker only tracked her deep sleep at 47 minutes and “claimed” she was awake for a total of 51 minutes throughout the night. Obviously, the customer didn’t think this accurate.

But there’s more. According to her, she found that, in her words, “the worse the quality of sleep I get, the more flattering the results are.” So, whenever she falls into a “drunken coma,” the tracker gives her great stats for her deep and light/REM sleep. In reality, though, she says she’s tossing and turning, can’t get back to sleep, and wakes up exhausted and feeling terrible.

This is huge especially because a number of users also agree with her.

So, it begs the question, how accurate is the Fitbit sleep tracker? We attempt answering this using research and facts. Come with us.

How Accurate Is The Fitbit Sleep Tracker? — Fitbit’s Side Of The Story

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So, apparently, Fitbit commissioned a study to check just how accurate a sleep tracker is. The results of the study came out and from what the researchers say, sleep trackers can determine the stages of sleep, that is, from wake and light sleep to deep sleep and REM, within a reasonable degree of accuracy in healthy adult sleepers.

For the study, 60 adults were tested, wearing three different devices. The adults were around 34 years old (give or take 10 years), and there were 36 male participants and 24 female participants.

The devices used include two fitness trackers, one on each wrist, as well as a Type III home sleep testing device. This sleep testing device is a device recommended by doctors to test conditions like sleep apnea at home. It acted as the control for cross-reference and comparison of results in this study.

Each of the trackers contained a photoplethysmogram that records cardiac activity and, of course, a 3D accelerometer that records movement.

When this test was finished, Fitbit’s lead sleep researcher, Dr. Conor Heneghan pronounced that the fitness trackers performed similar to or better than reports previously obtained from non-electroencephalogram (EGG)-based sleep studies.

It’s important to note that these EGG-based sleep studies combine the functions of respiratory, movement, and cardiac trackers in their testing. Also, being that they use electrodes to monitor electrical activity ongoing in the brain, they are respected as the most precise for sleep tracking.

However, from this study, Fitbit is saying that sleep trackers (including Fitbit sleep trackers) are not only better, they’ve also helped to simplify sleep research.

Before now, Fitbit has already said that the data obtained from the analysis of more than 4 billion sleep stages in its user data support the theories as held by sleep scientists.

How Accurate Is The Fitbit Sleep Tracker? — What The Sleep Experts Have To Say

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Despite the research that Fitbit have put forward, sleep experts don’t seem to be having any of that and are still very skeptical about the accuracy of fitness trackers in measuring sleep.

Hawley Montgomery-Downs is a sleep researcher and also an associate professor at the West Virginia University. In his study of the accuracy of sleep trackers, the researcher has come to the conclusion that sleep trackers are incapable of doing what they claim espeically when it comes to distinguishing sleep stages. 

According to him, these trackers are limited by the fact that they only include an accelerometer. These accelerometers can only monitor movement. But that’s not enough seeing as, regardless of what stage of sleep you’re in, deep or light, you tend to move the same amount of times as Montgomery-Downs explains.

In fact, sleep experts are worried that there might be more bad than good arising from using sleep trackers especially for users with sleep disorders.

Sleep is complicated as the National Sleep Foundation explains, and an analysis that is going to be meaningful and useful must be comprehensive and precise. The only test that can assure you of that, as the experts say, is a polysomnograph test.

Dr. Thanuja Hamilton echoes these same reservations about the accuracy of sleep trackers in this video. In her opinion, a better gauge for measuring sleep quality is how you feel during the day.

Sleep Trackers Vs Polysomnographs

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For a polysomnograph, the person to be tested would have to spend the night in a facility. There, the technologist would record a number of biological functions during sleep like eye movement, brain wave activity, heart rhythm, muscle tone, as well as breathing (which is much more than we can say for sleep trackers, by the way). They do this by placing electrodes and monitors on the chest, head, and legs.

On the other hand, a sleep tracker like Fitbit is a wearable device that only measures movement using an accelerometer. For this reason, therefore, the analysis can hardly be regarded as thorough. 

But then again, the polysomnograph test is not without its challenges. Sleeping in an unfamiliar bed in a strange facility can make one sleep a little less optimally than if they were in their own bed.

For this reason, many people might prefer to use a simpler device in the comfort of their beds being that it is more convenient and less expensive. Plus, for most healthy sleepers, it might not even make a huge difference.

Those with sleep disorders, on the other hand, such as insomnia should check in at a sleep facility for testing and not depend on a sleep tracker.

Issues With The Accuracy Of Sleep Trackers

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In February 2017, the Journal of Clinical Sleep Medicine carried a study that stated that the science to support the claims of these devices (sleep trackers) is insufficient, and many consumers don’t know this.

The main problem with fitness trackers such as the Fitbit sleep tracker, the study points out, is that it depends too much on the movement of the user to determine sleep levels. Besides that, experts also claim that the algorithms for sleep tracking are not transparent and that these devices tend to reinforce bad sleeping habits by making users stay longer in bed.

Fibit, in response to these comments, has said that the algorithm in their sleep tracker is accurate, being a product of “extensive internal testing.” 

This testing, Fitbit continues, involved the analysis of hundreds of nights of not just movement but heart-rate data as well. Fitbit said it used only clinical-grade equipment to obtain these data used and factored them into the creation of its algorithm.

In support of Fitbit, Dr Nathaniel Watson (a board-certified neurologist and sleep specialist University of Washington) seems to be of the opinion that a sleep tracker has its merits. In his opinion, it will help to encourage people to be more conscious of their sleep patterns, that is, quality and amount.

However, he still shares the same reservations as stated in the aforementioned study.

He says that it’s possible to invent a wearable device that tracks the stages of sleep accurately. However, he is yet to see anyone that currently does so and believes that Fitbit and other such manufacturers still need to do more research.

In summary, experts want to see Fitbit do a lot more research on their product before making any claims on its usefulness.

Some FAQs About The Fitbit Sleep Tracker’s Accuracy

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1. Why Is My Tracker Showing Me Few Hours Of Sleep Even Though You Sleep For Long Hours?

For instance, a certain customer says she goes to bed between 10 and 11 pm and wakes up at 7.30am in the morning. This should give about 8 to 9 hours of sleep. However, her tracker is only showing about half of that.

While this might mean that she’s really not sleeping well, the odds might also be that she has the tracker set to “Sensitive,” as a Fitbit employee points out. This might also be the case with you if you’re experiencing a similar problem.

What you want to do, therefore, is to change the settings to normal which, Fitbit says, works for most healthy sleepers.

You can do this by clicking on Account > Advanced Settings > Sleep Sensitivity. 

Or you can go to your dashboard at fitbit.com: Settings > Devices > scroll to Sleep Tracking.

According to Fitbit, “Normal” will count only significant movements like rolling over as being awake. “Sensitive,” on the other hand, records nearly all kinds of movements, significant or not, as awake time. 

Fitbit suggests that this setting might be better for people with sleep disorders as well as those who do not wear their tracker on their wrist when they go to bed.

Another reason your tracker might not be accurate might be as a result of out-of-date firmware, in which case, you’d have to update that.

Also, you might want to consider restarting your device. (Click here to read a similar article also on Fitbit devices: Why Won’t My Fitbit Charge?)

2. Why Does My Sleep Graph Say I Was Asleep When I Wasn’t?

Generally, sleep trackers are designed to automatically detect when the wrist is no longer on your wrist. However, sometimes, you might find that they recorded a sleep log when in actuality, you were awake. If this happens, you can simply delete the log from your Fitbit app.

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3. Can I Log Sleep In My Fitbit App Manually?

Fitbit devices would normally start and stop your sleep log automatically. However, if you feel this detection is inaccurate, you can start and stop sleep tracking yourself instead.

However, please note that you can’t do this on any Fitbit device with a heart-rate tracker that detects sleep stages.

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