All articles · Sleep trackers
Are sleep trackers actually accurate?
What does a tracker actually measure?
Watches and rings usually measure signals such as movement, heart rate and often photoplethysmography or temperature. Algorithms then infer sleep, wake and sometimes sleep stages. Separate the measured signal from the algorithmic estimate.
How do they compare with polysomnography?
A 2025 meta-analysis covering 24 studies and 798 participants found significant differences between consumer wrist trackers and polysomnography for total sleep time, sleep efficiency, sleep latency and wake after sleep onset. Meta-analysis.
A validation of six commercial devices found sleep-detection sensitivity above 90%, but substantially lower wake specificity and only fair-to-moderate agreement for sleep stages. Study.
What are they useful for?
- tracking usual bedtime and wake time;
- following trends over weeks;
- spotting large changes in sleep duration;
- bringing structured observations to a clinician.
What should you not conclude?
- that one poor score automatically means a sleep disorder;
- that a single night with little “deep sleep” is abnormal;
- that a consumer tracker can diagnose insomnia, sleep apnea or another condition without specific medical validation.
The American Academy of Sleep Medicine states that consumer sleep technology should not replace appropriate clinical evaluation for diagnosis or treatment. AASM position.