You can track REM sleep at home using a wearable device like a smartwatch, a fitness band, or a contactless bedside sensor. These tools estimate your sleep stages by measuring heart rate, movement, and breathing patterns throughout the night. None of them match the precision of a clinical sleep study, but they can give you a useful picture of your sleep architecture over time.
What Happens During REM Sleep
REM sleep is the stage most associated with vivid dreaming, memory consolidation, and emotional processing. Your brain becomes highly active during this stage, producing a mix of low-voltage electrical signals along with distinctive sawtooth-shaped waves. At the same time, your skeletal muscles go almost completely limp, a protective state called atonia that prevents you from physically acting out your dreams.
Your eyes move rapidly beneath your eyelids (hence the name), your heart rate becomes more variable, and your breathing grows irregular. These physical signatures are what tracking devices attempt to detect, each in their own way and with varying degrees of accuracy.
REM sleep makes up about 25% of your total time asleep. It follows a predictable pattern: your first REM period is short, often just a few minutes, and occurs roughly 90 minutes after you fall asleep. Each subsequent cycle grows longer, so most of your REM sleep is packed into the second half of the night. This is why cutting your sleep short by even an hour can disproportionately reduce REM time.
Wearable Trackers: What They Measure
Smartwatches and fitness bands from companies like Apple, Fitbit, Garmin, and Oura estimate sleep stages primarily through two sensors: an accelerometer that detects motion and an optical heart rate sensor (called photoplethysmography, or PPG) that shines light into your skin to measure blood flow changes with each heartbeat.
REM sleep produces a specific heart rate signature. Your heart rate variability shifts during this stage, with more activity in slower fluctuation patterns and less in faster ones. Wearable algorithms look for this shift, combined with the near-absence of body movement (reflecting muscle atonia), to flag a period as REM. Some newer devices also track breathing rate and blood oxygen levels, adding another data point to the algorithm.
The limitation is real: these devices are inferring sleep stages from indirect signals. They tend to be reasonably good at distinguishing sleep from wakefulness and at estimating total sleep time, but their accuracy drops when classifying individual stages like REM versus light sleep. Older actigraphy-style trackers that relied only on motion could detect sleep versus wake but couldn’t distinguish stages at all. Modern wearables have improved significantly by layering in heart rate data, but they still aren’t precise enough for clinical use.
Contactless and Bedside Sensors
If wearing something on your wrist disrupts your sleep, contactless options exist. Under-mattress sensors (like Withings Sleep Analyzer) and bedside radar devices use different approaches to capture the same basic signals. Under-mattress pads detect vibrations from your heartbeat and breathing through the mattress itself. Radar-based systems, like the one built into Google’s Nest Hub, use low-energy radar to pick up sub-centimeter body movements without cameras, microphones, or physical contact.
These devices track your breathing rhythm and micro-movements to estimate sleep stages. They’re convenient because there’s nothing to charge or remember to put on, but they face the same core limitation as wrist-worn trackers: they’re working with indirect data rather than measuring brain activity directly.
The Clinical Gold Standard
The only way to measure REM sleep with real precision is polysomnography (PSG), a clinical sleep study. This involves electrodes placed on your scalp to read brain waves, sensors near your eyes to detect rapid eye movements, and an electrode under your chin to measure muscle tone. REM is scored when all three signals line up: the brain shows an active, wake-like pattern, the eyes move rapidly, and chin muscle activity drops to its lowest point.
Sleep studies are typically ordered when a doctor suspects a specific sleep disorder like sleep apnea, narcolepsy, or a REM behavior disorder (where muscle atonia fails and people physically act out dreams). If you’re simply curious about your REM percentages, a clinical sleep study probably isn’t necessary or worth pursuing. Sleep clinicians generally don’t find the “deep sleep” versus “light sleep” breakdown from wearables clinically meaningful unless there’s reason to suspect an underlying medical condition.
How to Read Your REM Data
Most tracking apps display a hypnogram, a timeline showing when you were awake, in light sleep, deep sleep, or REM throughout the night. A healthy pattern shows REM periods getting progressively longer, with the most REM concentrated in the final few hours of sleep. You’ll also see a percentage or total minutes of REM sleep.
For a rough benchmark, about 25% of total sleep in REM is considered typical for adults. On seven hours of sleep, that’s roughly 105 minutes. Don’t fixate on any single night. Night-to-night variation is normal, and your tracker’s stage estimates carry meaningful margin of error. Look at trends over weeks instead. A consistent pattern of very low REM percentages, especially if paired with daytime grogginess or mood changes, is more informative than one bad night.
REM naturally decreases with age. If you’re in your 50s or 60s and notice lower REM numbers than guidelines suggest, that’s a normal part of aging rather than a sign something is wrong.
What Can Suppress Your REM Sleep
Several common substances significantly reduce REM sleep, which means your tracker data may reflect what you’re putting in your body more than how well your sleep system is functioning.
Alcohol is the most common culprit. It may help you fall asleep faster, but it fragments sleep architecture and suppresses REM, particularly in the first half of the night. Caffeine consumed too late in the day can delay sleep onset and compress the total sleep window, indirectly cutting into your later, REM-rich cycles.
Certain medications have a dramatic effect. Antidepressants reduce REM sleep to roughly 12.4% of total sleep time, compared to the normal 25%. Antipsychotic medications push it even lower, to around 8.8%. When both types are combined, REM drops to about 8.2%. These drugs appear to work partly by raising serotonin levels, which normally plummet during REM. If you’re taking any of these medications and your tracker shows unusually low REM, the medication is the most likely explanation.
Cannabis, antihistamines, and some blood pressure medications can also alter sleep staging. If your REM numbers look consistently off and you’re taking any medication, that context matters more than the raw numbers.
Getting More From Your Tracker
To get the most useful data from whatever device you’re using, keep a few things consistent. Wear your tracker snugly enough that the heart rate sensor maintains good skin contact. Charge it during the day so it doesn’t die overnight. Sleep in the same position relative to a bedside sensor.
Beyond the device itself, the habits that support healthy REM sleep are straightforward: keep a consistent sleep schedule so your body can complete a full set of 90-minute cycles, avoid alcohol within three hours of bedtime, and aim for at least seven hours of total sleep to give yourself enough time for later-night REM periods. Since REM is backloaded toward morning, sleeping an extra 30 minutes can add a surprising amount of REM time compared to the same 30 minutes added to the beginning of the night.
Track your data alongside a simple sleep diary noting what time you went to bed, when you woke up, and anything unusual (a late coffee, a stressful day, alcohol). After a few weeks, patterns emerge that the raw numbers alone won’t show you.