A sleep tracker is a gadget that records how long you sleep and guesses how well you slept, and the form it takes matters more than the brand. This guide compares the three common forms so you can pick one that fits your nights.
Start with what a sleep tracker really measures
Most trackers measure movement and heart rate, not brain waves. A sleep lab uses sensors on the head, and a home gadget does not. So when an app says you spent 90 minutes in deep sleep, that is an estimate built from motion and pulse.
The American Academy of Sleep Medicine said this plainly in a 2018 position statement. It noted that minimal validation data exists for consumer sleep products, and that most are self-described lifestyle or entertainment devices that are not subject to FDA oversight. It also said they are not substitutes for a medical evaluation.
That does not make them useless. They are good at showing patterns, such as when you go to bed, how long you stay in bed, and how steady your schedule is. Treat the stage charts as a rough guide.
Wrist bands and watches
A wrist tracker is the most common choice. Fitbit says its trackers and watches use your sleeping heart rate and movement to estimate time in light, deep and REM sleep, and to give a nightly Sleep Score. You wear the device to bed, and the app shows the results in the morning.
Apple takes a similar route. Its support page for Apple Watch sleep tracking says you can view time spent awake or in REM, Core, or Deep sleep, plus average time in bed and time asleep. It also lists heart rate and respiratory rate readings taken while you sleep.
The trade-offs are comfort and battery. Apple notes that a dead watch battery means no sleep data, and that a loose fit can make the motion sensor read too much movement. If you dislike wearing something at night, or forget to charge it, a wrist band may not suit you.
Under-mattress pads
A pad sits beneath the mattress, so there is nothing to wear. The Withings Sleep mat, listed at US$129.95 on the maker site, reports sleep cycles (deep, light and REM), heart rate and snoring. Its page says setup is a one-time job, and data syncs to the Health Mate app over Wi-Fi.
The strength of this form is that you cannot forget it. The weak spot is that it reads your body through a mattress, so a partner or a pet in the bed can blur the picture. Check how the maker handles two sleepers before you buy, and check that the pad suits your mattress.
Bedside devices
A bedside device stands on a nightstand and watches from a short distance. Google sells one in the Nest Hub (2nd gen), a smart display with a Sleep Sensing feature. Its store page says Sleep Sensing tracks your sleep and gives you personalized insights and tips, and that Google offered a preview of it throughout 2023. The display uses Motion Sense, which detects movement without a camera.
This form asks nothing of your body, but it takes space and a power cord. It also has a microphone and a screen in your bedroom. Look for a mic off switch and read the privacy notes. The Google Store page says you can turn off the mic at any time with the mic switch.
Check comfort, data and the shopping list
Before you buy, run through four questions. Will you wear it, plug it in or slide it under a mattress every night? Does it list what it senses, such as motion, heart rate or sound? Does the app let you see the raw numbers, or only a score? Does the maker say the device is not for diagnosis?
Data export is the question most buyers skip. The AASM statement points out that raw data and the formulas behind the scores are usually not available. If you want to keep your own record, look at the maker help pages first and see whether you can download your history.
Last, be honest about the goal. The AASM statement says a person who tracks their snoring may be at risk for obstructive sleep apnea and may need validated testing. If you are worried about your sleep, talk to a doctor. A tracker can start the conversation, but it cannot end it.