Part 1 · Sleep
Everything starts with the breath
The most important input for sleep analysis is the respiratory waveform: the pattern of breathing in and out. That pattern tells the sensor whether a person is asleep and, if so, how deeply. Every sleep figure below is built on this one measurement.
01Sleep depth (Awakeness)
How awake the person is, read continuously from 0 to 1.
02Sleep time
Total time read as asleep within a fixed daily window.
03Movements during sleep
How many movement events happened while asleep.
04Movement duration
How long those movements lasted in total.
05Sleep score
How much real recovery the person got from sleep.
Sleep metrics
Five measures, one picture of the night
01Sleep depth (Awakeness)
Awakeness is a value from 0 to 1. Closer to 0 means deeper sleep; closer to 1 means more awake. Above 0.88 the person is read as awake, below 0.88 as asleep.
- Each value is computed from the previous 10 minutes of data. "Asleep now" means the last 10 minutes looked like sleep.
- The web dashboard shows awakeness at up to 3-second resolution; the mobile app at up to 5-minute resolution.
- Some reports show sleep intensity instead. It is the same measure turned around (1 minus awakeness), so closer to 1 means deeper sleep.
02Sleep time
Sleep time is the total time read as asleep, added up over a fixed day that runs from 08:00 to 08:00.
- Daytime naps are included.
- Sleep that continues past 08:00 counts toward the next day.
- The figure is updated once a day, normally between 08:30 and 09:00, after the calculation runs.
0304Movements during sleep, and their duration
The sensor continuously measures physical change in the space (see the Movement Index in part 2). Each time that change crosses a set level, it counts as one movement. A single continuous movement counts once, however long it lasts. Duration uses the same measurement and adds up how long the movements lasted across the sleep period.
05Sleep score
The sleep score, from 0 to 100, is one of the most important figures. It represents how much real recovery the person got from sleep. It is calculated mainly from sleep depth, accumulated over the time asleep.
Shallow sleep, same hours
Less recovery, so a lower score than someone who sleeps more deeply for the same time.
Shallow sleep, long hours
Total recovery can still be high. A weak charger left on long enough still fills the battery.
Deep sleep, too short
Even very deep sleep may not score high if there is not enough of it.
Two people who sleep the same number of hours can therefore earn very different scores, and a long night can make up for shallow sleep. The sleep score is an absolute measure, so it can be compared between people.
A score comes entirely from sleep time and sleep depth, so a low score can be traced to short sleep, shallow sleep or both. Why the sleep was short or shallow has many personal causes that the sensor cannot see.
Reading the sleep chart
One night on the sleep chart
The sleep chart puts the whole night on one screen: how deeply the person slept, when they moved, when the room was empty, and their breathing rate while at rest. The example below is from the XKare app (Sleep Score card → Sleep Chart). The 5 min and 30 min buttons at the top right set how much time each point covers.
What each mark means
| Mark | Meaning |
|---|---|
| Background colour | Light green: someone is in range (occupied). Light pink: the room is empty (vacant). Grey: the sensor is offline. |
| Purple line · sleep intensity | How deeply the person is sleeping. The lower the line, the deeper the sleep; at the top it reaches Awake. |
| Green dots · asleep | Each dot covers one 5- or 30-minute interval. The bigger the dot, the more of that interval was spent asleep. |
| Yellow dots · sleep disturbance | Movement while asleep. The bigger the dot, the more often the person moved in that interval. |
| Blue dots · respiratory rate | Breaths per minute, shown only while the person is resting or asleep (right-hand axis). Values higher or lower than the person's usual are highlighted. |
Reading the night
A typical night moves through the stages below. Follow the purple line from left to right and use the dots to confirm what you see.
| Stage | What it looks like on the chart |
|---|---|
| Trying to fall asleep | The person is in bed and still: the background is green and blue breathing dots appear, but the purple line is still near Awake and there are few or no green dots. The line starting to fall marks the start of the effort to sleep. |
| Light sleep | The line sits in the middle of the scale, below Awake but well above Deep Sleep. Green dots appear. |
| Deep sleep | The line drops close to Deep Sleep and the green dots are at their largest. |
| Brief awakening | A short, sharp rise of the line toward Awake that falls back again. Most people do not remember these. |
| Movement during sleep | Yellow dots. Larger dots mean more frequent movement in that interval; they often line up with brief awakenings. |
| Left the room | The background turns pink (vacant) and the dots stop. When the person returns, the background turns green again. |
| Wake-up | The line rises back to Awake and stays there, and the green dots end. |
Live View, next to the Sleep Chart button, is built the same way with the latest data, and a dashed vertical line marks the present moment. Once the sleep chart is familiar, Live View reads the same way.
Sleep questions
Accuracy and common questions
How do we know the data holds up?
Self-check: sleep time
The easiest check. People generally know when they fell asleep and woke up, so the measured sleep time can be compared with their own experience.
Clinical validation: PSG
Sleep depth is being validated against polysomnography, the clinical sleep-study standard. Results will be published later.
"Sleep time looks shorter than I actually slept."
Medically, wakefulness is defined by brain activity, and people have many brief arousals they never remember. A small gap between measured and remembered sleep is normal. If the gap is more than about one hour, the usual causes are:
1Sensor placement
The distance or angle is off, so readings are not captured correctly.
2Noise source
Something near the sensor moves or vibrates and disturbs the measurement.
3Irregular breathing
A condition such as COPD can make breathing irregular enough to be read as awake.
Check the sensor's distance and angle. If those are right, move the sensor in case a nearby noise source is the cause.
- How is real-time sleep or wake decided?
- From awakeness: below 0.88 over the previous 10 minutes is asleep, above is awake.
- What is a "good" sleep score?
- Higher is better: more recovery from sleep. Because the score is absolute, it can be compared between people and from one night to the next.
- Does leaving the bed or restlessness count?
- Time out of the room is not sleep, so it does not add to sleep time. Movement while asleep is reported separately as movements and their duration.
Part 2 · Movement Index
A measure of how much someone is moving
The sensor takes a fresh reading of the space many times every second. The Movement Index reflects how much changes between one reading and the next. When the person lies still, the readings barely change and the number stays low. When they move, the readings change and the number goes up. It is sometimes called the motion index or motion score; it is the same thing.
How it works: spotting the difference between two snapshots
For the technically minded: if xn[k] is the radar frame received at time n, the Movement Index is Σk |xn[k] − xn−1[k]|, the summed difference between one reflected frame and the previous one.
What affects the value
Because the sensor measures movement from across the room through reflected radio signals, a few things besides the movement itself can change the number, even for exactly the same motion.
Movement size
Bigger movements give a higher number. This is the main driver.
Distance
A person farther from the sensor can read differently.
Body position and angle
How the person lies, and which way they move relative to the sensor.
Body and bedding
Body size and blankets change how strongly movement shows.
Reading the number: there is no single "normal"
The Movement Index is not like temperature or heart rate. It has no unit, no fixed normal and no universal "high" or "low". The same number can mean different things for two different patients or two different rooms.
Don't
Compare one patient's number with another's, or with a fixed limit, as if it were an exact measurement.
Do
Compare a number with the same patient's own usual pattern, in the same bed and the same room.
Daily use: read it as each patient's own trend
With the sensor fixed on the wall and the patient in the same bed, the setup stays the same night after night. Changes in the Movement Index over time then reflect real changes in how much the patient moves, not changes in the equipment.
1Know their usual
Get a feel for each patient's typical range over a few nights.
2Watch the trend
Follow the number across nights rather than reading a single value.
3Notice changes
New restlessness, or unusual stillness, stands out against their normal.
If the sensor is moved, the bed is moved, or a new patient takes the bed, the earlier values are no longer a fair comparison. Start a new "usual" from that point.
Movement questions
Quick answers
- What does it show?
- How much a person is moving, moment to moment.
- How does the sensor get it?
- By comparing each reading with the one just before and adding up the change.
- Is there a "normal" to compare against?
- No fixed normal. Compare with the patient's own usual pattern.
- What counts as "high" or "low"?
- Only meaningful against that patient's own usual range, in the same bed and room.
- How do we use it day to day?
- Watch each patient's trend over time, in the same bed.
- What can change the number?
- Mainly how big the movement is, plus distance, body position and angle, and body size and bedding.