Do Sleep Trackers Work? What They Can and Can't Tell You
Share
Your watch says you got 6 hours 12 minutes, 48 minutes of deep sleep and a sleep score of 71. It sounds precise. But how does a band on your wrist know what your brain was doing? This guide covers whether sleep trackers work, what they get right and wrong, and when you're better off without one.
The short answer: sleep trackers are fairly good at telling when you were asleep and for how long. They're much less reliable at sleep stages, such as deep and REM sleep, and they tend to miss time spent lying awake. They're useful for spotting patterns in your bed and wake times, not for diagnosing a sleep problem. If the numbers make you anxious, stop tracking.
How sleep trackers work
The gold standard for measuring sleep is a sleep study in a lab, which records brain activity. A wearable can't do that. The Sleep Health Foundation explains that these devices measure your sleep with an accelerometer, a sensor that measures your movement (source). Many also use heart rate. From those signals, software estimates when you were asleep and guesses at the stages.
How accurate are sleep trackers?
| What they measure | How well |
|---|---|
| Whether you're asleep | Good. In lab tests, devices agreed with a sleep study around 86 to 89% of the time |
| Total sleep time | Reasonable, but often a little generous |
| Time awake in the night | Weak. Lying still and awake often gets counted as sleep |
| Sleep stages (deep, light, REM) | Poor to mixed. Agreement was 50 to 65% in one Australian test of six wearables |
| Sleep score | Unclear. The Sleep Health Foundation notes it's often unclear how these scores are worked out |
Those figures come from studies that tested consumer devices against lab sleep studies, including one at CQUniversity's Appleton Institute in Adelaide, which concluded that all six devices needed improvement at measuring sleep stages.
The Sleep Health Foundation's summary is that these devices can usually tell when you are asleep, but they are not very good at telling what sleep stage you are in.
What a tracker can't tell you
- Whether you have a sleep disorder. The American Academy of Sleep Medicine's position is that consumer sleep technology can't be used to diagnose or treat sleep disorders, and isn't a substitute for a medical evaluation (source).
- Why you slept badly.
- How you feel. A score of 85 doesn't mean much if you're exhausted, and a 60 doesn't matter if you feel fine.
When tracking makes sleep worse
Some people get so focused on their sleep data that it becomes a source of stress. Sleep doctors have described this as orthosomnia: a preoccupation with getting perfect sleep numbers. It was first described in a small number of patients, so it isn't a formal diagnosis, but the pattern is familiar.
The Sleep Health Foundation gives a similar warning: if you have insomnia, tracking sleep might lead to anxiety about not getting enough sleep.
Signs your tracker isn't helping:
- You check your score before you've noticed how you feel.
- A bad score ruins your morning.
- You lie in bed longer trying to improve the numbers.
- You worry at bedtime about what tomorrow's score will be.
If that's you, take it off at night for a few weeks.
When a sleep tracker is useful
- Seeing your real bed and wake times. Most people overestimate how regular they are. The Sleep Health Foundation suggests it may be more helpful to look at the patterns of your bed and wake times over time.
- Testing a change. Did the earlier bedtime last all week, or two nights?
- Starting a conversation with your GP, as long as you both treat the data as a rough guide.
Do you need a tracker to sleep better?
No. The habits that improve sleep don't need data: a regular wake-up time, morning light, a caffeine cut-off and a dark, quiet bedroom. See our sleep hygiene checklist and how much sleep do I need?
A simple sleep diary works too. Write down when you went to bed, when you got up, and how you felt. That last column is the one no tracker has.
Tracker, smartwatch or simple alarm?
Many people buy a smartwatch for the silent alarm and end up with sleep scores and notifications they didn't ask for. If all you want is to wake up on time without waking anyone else, you don't need a tracker at all. We compare the options in smartwatch vs vibrating alarm wristband.
Where the Sovune Nudge fits
We make the Sovune Nudge, a vibrating alarm wristband, so we're not neutral. It's deliberately not a tracker:
- No sleep scores, no app and no data. It does one thing: wakes you up.
- No screen time at night. It's set on the band, with no phone needed.
- Up to 14 days per charge, where many trackers and smartwatches need charging every day or two.
- Silent, with three intensity levels that build over a full minute.
It comes with a 30-day money-back guarantee.
Quick answers
Are sleep trackers accurate? They're fairly accurate at telling sleep from wake and estimating total sleep time. They're much less accurate at sleep stages.
Can a sleep tracker detect deep sleep? Only roughly. Without measuring brain activity, a wearable is estimating from movement and heart rate.
Can a sleep tracker diagnose sleep apnoea or insomnia? No. Consumer trackers aren't diagnostic devices. See your GP if you're worried.
Should I stop using my sleep tracker? If the numbers make you anxious or you trust them over how you feel, take a break from it.
For every type of silent alarm compared, see our complete guide to vibrating alarms in Australia.