What Is REM Sleep?
REM (rapid eye movement) sleep is a stage with vivid dreaming and an active brain, more common in the second half of the night. Laboratories measure it with EEG; consumer trackers only estimate it.
Key points
- What it is. A distinct sleep stage with eye movements and dreaming.
- When. REM periods lengthen towards morning, which is why short sleep cuts REM.
- Trackers. They infer stages from movement and pulse; treat percentages as rough.
What it is
A distinct sleep stage with eye movements and dreaming.
When
REM periods lengthen towards morning, which is why short sleep cuts REM.
Trackers
They infer stages from movement and pulse; treat percentages as rough.
Frequently asked questions
Do I need more REM?
Normal, sufficient sleep supports it.
Can I boost it?
Regular timing and enough sleep.
Sources
- de Zambotti M, et al. Wearable sleep technology in clinical and research settings. Med Sci Sports Exerc 2019;51(7):1538–1557. PubMed
Links go to PubMed searches for the paper title or to the official guideline or regulator page. Standards and regulations are revised, so check the current edition before relying on them. Mattress and pillow research is limited; treat findings as a starting point.
Keep reading
Sleep Technology: Trackers, Apps and Smart Devices Explained
What sleep trackers, apps and smart devices can and cannot tell you, with the evidence on accuracy and who benefits.
Read more →Sleep technologyWhat Is a Sleep Tracker and How Does It Work?
How wearables and under-mattress sensors estimate sleep, what they get right and wrong, and who benefits.
Read more →Sleep technologyWhat Is Deep Sleep and How Is It Estimated?
Slow-wave sleep explained, how laboratories measure it and how wearables estimate it.
Read more →Sleep technologyHow Accurate Are Consumer Sleep Trackers?
What validation studies find: good at total sleep, weaker at stages and wake detection.
Read more →Sleep healthHow Much Sleep Do Adults Really Need?
What AASM, the Sleep Research Society and the National Sleep Foundation say about recommended sleep for adults.
Read more →This article is general information, not medical advice. If you have persistent pain or sleep problems, please speak to a doctor.
Related reading
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