Sleeping with a bunch of fitness trackers

The best tracker is the one that doesn’t keep you awake

There are few things as good for you as a good night’s sleep. Sleep replenishes body and mind and keeps you operating at optimal levels. If you want to track your sleep habits, you’ll find that many smartwatches and fitness trackers come with sleep-tracking capabilities. The best fitness tracker for sleep is one that’s comfortable to wear in bed, provides accurate data and lasts all night.

Best fitness trackers for sleep monitoring

Fitbit Versa 4

The testing team found the Fitbit Versa 4 to be thin, lightweight and comfortable to wear while sleeping.

At a fraction of the cost of other options, the Fitbit Versa 4 impressed us with the overall accuracy of its sleep tracking, recording various sleep stages that you could then examine in its companion app. For more granular data, you do need to subscribe to the Fitbit Premium service. Nevertheless, it was comfortable to wear, and its battery life impressed, taking two days just to get down to half capacity.

Apple Watch Ultra 2

The Apple Watch Ultra 2 provides scheduled sleep times and soothing wake-up alarms.

It might look crazy to use something this big and rugged as a sleep tracker, but the Apple Watch Ultra 2 surprised us the most with its comfort. Made of titanium, which is lighter and stronger than steel, the Ultra 2 was easy for us to forget despite its size and dazzling screen. That screen gets as dim as 1 nit, too, so it won’t disturb you if you glance at it at night. Apple’s Health app provides sleep-stage tracking, heart rate and breath rate, and works with the watch functions to provide scheduled sleep times and soothing wake-up alarms.

Apple Watch Series 9 

The Apple Watch Series 9 can estimate your time spent in bed even if you’re not wearing it.

The sleek lines of a flagship Apple Watch like the Series 9 made it easier to wear to bed than some other options, and it delivered clear results that didn’t make any demands. Like the Ultra 2, the Apple Watch Series 9 has a bright screen that can get as dim as 1 nit in a dark room. Its gently rounded corners and edges make it less obtrusive than other fitness trackers and smartwatches we tested, especially when paired with a soft fabric watch band. It tracks the same metrics as the Ultra 2 and, notably, can estimate time spent in bed even if you’re not wearing it.

Garmin Vivoactive 5

The Garmin Vivoactive 5 provides sleep coaching to help you improve your overall sleep score.

The Vivoactive 5 from Garmin is an excellent value overall for a fitness tracker with smartwatch capabilities. As a sleep tracker, its data was accurate and thorough based on our comparison with other devices. It provides statistics such as total hours of sleep, sleep stages and sleep movement, and your “sleep coach” provides recommendations based on this data to help you improve your overall sleep score. While some may find its bulky design uncomfortable to wear in bed, if you don’t anticipate that being an issue for you, for goal-oriented types, the Vivoactive 5 provides all the information you need and then some.

Benefits of using fitness trackers for sleep monitoring

Sleep monitoring can do more than tell you how long you slept. Fitness trackers can measure how many times you wake up, how much time you spend asleep versus simply lying in bed, and estimate how long you spend in various stages of sleep.

Sleep stages tracking

Our sleep can be divided into three stages, with various effects and benefits.

• Light sleep: Also known as core sleep, this stage usually makes up the majority of sleep you get in any given sleep cycle and may aid in cognition.
• Deep sleep: A stage that makes up the shortest amount of any given sleep cycle. Deep sleep seems to be when the body physically grows and repairs itself. This stage is also associated with delta waves in the brain.
• REM sleep: The final stage of a sleep cycle is REM or rapid-eye movement sleep, when most of our dreaming takes place. This stage seems to be important in the formation of long-term memories and brain function.

Sleep duration and quality

How long we sleep versus how long we need to sleep varies from person to person, but getting less sleep than we need is always a bad thing.

• Total sleep time: This is the total amount of time you spend sleeping. Fitness trackers and smartwatches may have different ways of calculating sleep time versus time spent awake in bed.
• Sleep efficiency: This is the percentage of time spent in bed compared to the percentage of time actually sleeping. Not all fitness trackers or smartwatches calculate your sleep efficiency for you, but you can easily see it for yourself.
• Awakenings: Fitness trackers can detect periods of wakefulness during a sleep period, from simply stirring so briefly you don’t even remember it, to getting up to use the bathroom or get a drink of water. These will negatively impact your overall sleep score. 

Choosing fitness trackers for sleep monitoring

Accuracy

It can be difficult for a consumer to know how accurate a fitness tracker is at sleep monitoring. These devices don’t measure sleep directly, but infer your sleep based on data they gather from movement and heart rate sensors. No consumer device currently compares to the accuracy of a medical sleep study.

Our top picks: Accuracy

• Fitbit Versa 4: In our sleep testing, the Versa 4 seemed reasonably accurate, reflecting our tester’s sleep patterns consistently with their experience.
• Apple Watch Ultra 2: The Ultra 2’s data were also measured against those of a different device, with consistent results from each.
• Apple Watch Series 9: The Series 9 has the same third-generation heart rate sensor as the Ultra 2, allowing it to estimate sleep stages with the same accuracy. It even correctly estimates time spent in bed despite not being worn.
• Garmin Vivoactive 5: We compared the results of the Vivoactive with another sleep tracker and found its results highly consistent with the control data.

Comfort and wearability

The key to accurate sleep tracking is comfort: if a fitness tracker is uncomfortable to wear in bed, you’re probably not going to want to sleep in it consistently.

Our top picks: Comfort and wearability 

• Fitbit Versa 4: We found the Versa 4 reasonably comfortable to wear in bed for sleep-tracking purposes.
• Apple Watch Ultra 2: A consistent finding in our testing is how surprisingly unnoticeable the Apple Watch Ultra 2 is on the wrist, despite its size and rugged design.
• Apple Watch Series 9: This is generally a comfortable watch to sleep in, especially if you use a softer fabric strap or watch band.
• Garmin Vivoactive 5: Unfortunately, despite the in-depth metrics and sleep score features of Garmin, we felt the Vivoactive 5 too bulky and uncomfortable to sleep in, but someone less sensitive may feel otherwise.

Battery life

When it comes to sleep tracking, you need a fitness tracker or smartwatch that not only lasts a full day of activity, but also all night without running out of charge.

Our top picks: Battery life 

• Fitbit Versa 4: The Versa 4’s battery took two full days just to drop to 50% in our testing, and took only an hour’s charging to return to 100%, which makes it excellent for wearing all night to record your sleep.
• Apple Watch Ultra 2: The Ultra series has better battery life than other Apple Watches. We got 72 hours of battery life out of it, consistent with Apple’s claims when using low-power mode.
• Apple Watch Series 9: During our testing, the Series 9 lasted 14 hours of active use and eight hours of standby. You’ll need to charge it before or after using it for sleep tracking.
• Garmin Vivoactive 5: Garmins are known for their fantastic battery life. The Vivoactive 5 lasted almost one full week. Even with its GPS on all the time, it lasted a whole day.

How we tested sleeping with fitness trackers

We tested fitness trackers and smartwatches in real-life situations including wearing them to bed with sleep tracking enabled. For sleep tracking, we noted how easy it was to set up sleep tracking and how detailed the sleep data was afterward, as well as how much data we could access on the watch itself versus on a smartphone with an app. We specifically paid attention to:

• Comfort: We noted weight, shape, strap material and other factors that made for a comfortable or uncomfortable experience while sleeping, especially in different sleep positions
• Accuracy: Whenever possible, we compared the data gathered against a second control device and our own subjective notes or experiences of our sleep cycle
• Battery life: We measured how long it took for the battery of each device to run down, noting especially if after a full day of wear, the battery was too low to wear overnight.

Aside from the devices listed here, we also tested the Samsung Galaxy Watch6 and Watch6 Classic as well as the second-generation Apple Watch SE. We didn’t feel that either Samsung was particularly accurate with their sleep tracking, at least in our testing, while the Apple Watch SE was less comfortable to wear to bed than the other Apple Watches..

Conclusion: Fitness trackers can help you get better sleep

Wearing a smartwatch or fitness tracker to bed each night can give you fascinating insights into your sleep habits. Over time, you’ll come to notice what’s normal for you, as well as what might trigger a poor night’s sleep (such as a lack of exercise). 

The last thing you want to do, however, is make your fitness tracker become the source of sleep anxiety rather than a remedy; you don’t want a fitness tracker to keep you up worrying about how well you’ve slept. At the end of the day, everyone has different sleep needs. And if you do get a poor sleep score, don’t fret — just consider it a good excuse to take a nap.   

Our expertise

Jmar Gambol is a writer, product tester and experienced sleeper who personally tested several smartwatches for BestReviews, including sleep tracking. He has worn a smartwatch to bed regularly but has learned to take it off if it’s going to bother him overnight.

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