Do Sleep Trackers Work? What Wearables Can and Cannot Tell You
Smartwatches, rings and bedside gadgets promise to tell you how well you slept. They can be useful, and they can also make you obsessed with a number. This guide explains what trackers do well, where they struggle and how to use them without losing sleep over the score.
Key takeaways
- Trackers are decent at estimating when you were asleep and awake over time.
- Their estimates of sleep stages are less reliable than a laboratory study.
- Use trends and how you feel, not a single night’s score.
How trackers work
Most devices use movement and heart rate, and some add skin temperature and blood oxygen, to estimate sleep. They then apply algorithms to guess sleep stages. Because they do not measure brain activity directly, stage estimates can be off.
What they are good for
- Seeing how regular your bedtime and wake-up time really are.
- Spotting trends after changes such as less caffeine or an earlier bedtime.
- Noticing that your sleep is much shorter than you thought.
Our sleep calculator and a simple log can do much of that without any hardware.
Where to be careful
Do not treat a “sleep score” as a diagnosis. Some people develop anxiety about perfect sleep data, a pattern sometimes called orthosomnia, which can itself make sleep worse. If a tracker makes you worry, take it off for a few weeks.
Privacy
Sleep data is health data. Read the privacy settings, check whether data is shared or sold and use strong passwords. Prefer devices that let you export or delete your data.
When data should prompt a doctor visit
Repeated records of low blood oxygen, loud snoring or long breathing pauses should be taken to a doctor, but only a proper sleep study can diagnose apnea. See sleep apnea.
Frequently asked questions
Are sleep trackers accurate?
They are reasonably good at telling sleep from wake over a night and less accurate for individual sleep stages.
Do I need a tracker to sleep better?
No. A consistent routine and a simple diary give most of the benefit.
References and further reading: Validation studies of consumer sleep trackers in Sleep and the Journal of Clinical Sleep Medicine; Baron et al., 2017, Journal of Clinical Sleep Medicine (orthosomnia).