Open last night in Voke and the first thing you see is a chart with four rows: Awake, REM, Light and Deep. The line steps between them through the night. Here’s what each row means, what a healthy night tends to look like, and how much to trust it.
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October 4The four stages
Sleep scientists split sleep into REM sleep and three stages of non-REM sleep, called N1, N2 and N3 in the American Academy of Sleep Medicine’s scoring manual. Watches and rings fold N1 and N2 together as “light”, which is what Voke shows too.
- Light. N1 is the short drift between awake and asleep. N2 is where your heart rate and breathing slow and your body temperature drops. Together they make up the largest share of a night, often around half of it or more (StatPearls, NIH). Apple calls this stage “Core”. Voke shows it as Light.
- Deep. N3, or slow-wave sleep. It’s the hardest stage to wake from, and the stage the NIH ties to tissue repair and hormone release.
- REM. Rapid eye movement sleep, when most vivid dreaming happens. Your brain is busy, and your muscles go slack so you don’t act out your dreams. In adults, REM is roughly a fifth to a quarter of the night (StatPearls).
- Awake. Time awake after you first fell asleep. A healthy night still has some.
What a night tends to look like
Sleep runs in cycles. You go from light to deep, back up through light, then into REM, and start again. The first REM comes about 90 minutes after you fall asleep (NIH). Later cycles run roughly 90 to 120 minutes (StatPearls), so a full night holds four or five of them.
The cycles aren’t all alike. Early in the night they hold long stretches of deep sleep and short REM. As the night goes on, deep sleep shrinks and REM grows. Near morning, you spend almost all your time in light and REM (NIH).
So on a typical chart, expect:
- most of the deep sleep in the first third of the night;
- REM blocks that get longer toward morning;
- light sleep running through the whole thing;
- a few short spells awake, often between cycles.
Age changes the shape. A large analysis of 65 sleep studies found that in adults, the share of deep sleep goes down with age, and time awake after falling asleep goes up (Ohayon et al., Sleep, 2004). A 60-year-old with less deep sleep than they had at 25 isn’t seeing a fault in their tracker.
For total sleep, the American Academy of Sleep Medicine and the Sleep Research Society recommend that adults get 7 hours or more a night, regularly (Watson et al., 2015).
What else is on the screen
Along with the chart, the sleep screen shows:
- Total asleep, above the chart, with a plus or minus figure. That compares last night with the average of the 14 nights before it.
- Stages. Minutes in each stage for the night.
- Consistency. When you fell asleep and woke up over the last 14 nights.
- Overnight. Your heart rate through the night, with its lowest point and when it happened, and your heart rate variability (HRV) with its average.
- Time in bed, efficiency and breathing rate, when your source sends them. Efficiency is time asleep as a share of time in bed.
- Naps, listed on their own. They don’t count toward the night’s total. Do naps hurt your night’s sleep? looks at what they do to it.
Not every device records stages. If yours only knows asleep from awake, Voke draws two rows, Asleep and Awake. If it only sends a total, you see the total.
How far to trust it
A sleep lab tells stages apart by measuring brain waves. Your watch can’t. It estimates stages from movement and heart rate. Studies comparing consumer trackers with lab sleep tests find most are good at telling sleep from wake, but less reliable at telling one stage from another, and worse on disturbed nights (Chinoy et al., Sleep, 2021).
So read stages as a rough sketch, not a measurement. One night with little deep sleep means very little. A pattern over weeks is worth more, and it’s most useful when you compare your own nights against each other, on the same device. The History tab shows them side by side. If two devices record the same night, Voke keeps one of them.
Not medical advice
Voke shows what your device recorded. It doesn’t diagnose anything. If you’re tired most days despite a full night in bed, if someone tells you that you stop breathing or snore loudly in your sleep, or if you can’t sleep most nights, talk to a doctor. Your chart can be a useful thing to bring along. It isn’t a substitute for the visit. Our health disclaimer says more.
Sources
- American Academy of Sleep Medicine: The AASM manual for the scoring of sleep and associated events
- Patel et al., StatPearls, NIH National Library of Medicine: Physiology, sleep stages
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH: What happens during sleep?
- Ohayon et al., Sleep, 2004: Meta-analysis of quantitative sleep parameters from childhood to old age in healthy individuals
- Watson et al., Sleep, 2015: Recommended amount of sleep for a healthy adult
- Chinoy et al., Sleep, 2021: Performance of seven consumer sleep-tracking devices compared with polysomnography