Sensors infer sleep
Most wearables combine motion sensing with optical pulse data. Algorithms look for patterns associated with sleep, wakefulness, and—on some devices—estimated sleep stages.
Estimates are not a sleep study
Wearables can misclassify quiet wakefulness as sleep and their sleep-stage estimates have limitations. Treat detailed stage labels as estimates, especially when they conflict with how you feel or a clinician’s assessment.
Use the trend, not the verdict
A regular record can help you notice changes in schedule, duration, or restfulness. It cannot diagnose insomnia, sleep apnea, or other conditions.
A note on health information
This article is for general education, not medical advice. GRND is not a medical device. For symptoms, diagnosis, treatment, or urgent concerns, contact a qualified healthcare professional or local emergency service.