Actigraphy is a clinical sleep test that uses a watch-like movement sensor to estimate when you sleep and wake over several days or weeks. It is especially useful for seeing sleep timing, duration, and day-to-day variability in your usual environment.
Actigraphy does not directly detect sleep. It cannot measure sleep stages, breathing, oxygen, or brain activity, and it does not diagnose most sleep disorders by itself. A clinician interprets the estimates alongside your symptoms, medical history, and usually a sleep diary 1.
How actigraphy works
An actigraph contains an accelerometer that records movement. Software divides the recording into short intervals and uses an algorithm to classify each interval as likely sleep or likely wake. Clinical devices are usually worn on the wrist or ankle and can record continuously for days to weeks 1.
Some devices also have a light sensor or an event button. Your clinic may ask you to press the button when you try to sleep and when you get up. The movement data, event markers, and diary entries help the clinician decide which parts of the recording belong to your intended sleep period.
The result is often shown as an actogram, a chart of activity and rest across each 24-hour day. Rather than focusing on one night, the chart can reveal a consistently late schedule, changing bedtimes, short sleep on workdays, catch-up sleep on days off, or frequent naps.
What actigraphy can estimate
Depending on the device and scoring method, an actigraphy report may include:
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Sleep onset and sleep offset: Approximately when sleep began and ended.
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Total sleep time: The estimated amount of sleep during the main sleep period and, sometimes, across the full day.
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Sleep latency: The estimated time between trying to sleep and falling asleep.
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Wake after sleep onset: Estimated wake time after sleep first began.
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Sleep efficiency: Estimated sleep time as a percentage of the time set aside for sleep.
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Timing and variability: How the sleep schedule changes across workdays, free days, and naps.
Each value is an estimate derived from movement. A report may look precise to the minute, but that does not make every minute an exact measurement.
When clinicians use actigraphy
The American Academy of Sleep Medicine (AASM) makes conditional recommendations for several clinical uses. A conditional recommendation means the test may be helpful, but it is not necessary or appropriate for every patient 1.
Insomnia
Most people do not need actigraphy for a routine insomnia diagnosis. It can be useful when an objective estimate would change a decision, such as when reported sleep and other clinical information do not agree or symptoms have not improved as expected with treatment 1.
Actigraphy can show patterns that differ from a diary, but neither record proves what a person experienced while lying awake. Someone with insomnia may remain very still, which the device can mistake for sleep.
Circadian rhythm sleep-wake disorders
Because actigraphy records across many days, it can help show whether sleep consistently occurs earlier, later, or at a changing time. The AASM suggests it as part of the assessment of circadian rhythm sleep-wake disorders in adults and children, although the evidence behind that recommendation was limited by small studies 1.
A diary is still valuable because it records intent and context, such as when you went to bed early but did not try to sleep or when a work shift changed your schedule.
Insufficient sleep
Actigraphy can help estimate whether an adult is repeatedly getting too little sleep. AASM guidance suggests a recording period of two to three weeks or longer when clinicians are evaluating suspected insufficient sleep syndrome 1.
This longer view can distinguish a persistently short sleep opportunity from a single unusually bad night.
Before a daytime sleepiness test
The Multiple Sleep Latency Test (MSLT) measures how quickly a person falls asleep during scheduled daytime naps. Too little sleep before the test can complicate interpretation. Current AASM protocol recommends documenting sleep with a diary and, when available, actigraphy for two weeks before an adult MSLT 2.
Actigraphy does not replace the overnight polysomnogram performed before an MSLT.
Alongside a home sleep apnea test
Some home sleep apnea test systems integrate actigraphy to estimate how much of the recording was probably spent asleep. This may help calculate breathing events against estimated sleep time rather than the full recording time 1.
Actigraphy alone cannot diagnose sleep apnea. It does not measure airflow, breathing effort, or blood oxygen.
What actigraphy cannot tell you
Actigraphy is not the right tool for every sleep question:
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It cannot identify sleep stages. REM, light, and deep sleep require signals such as brain waves, eye movements, and muscle activity that actigraphy does not record.
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It cannot diagnose sleep apnea by itself. Movement does not show whether breathing repeatedly stops.
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It cannot diagnose periodic limb movement disorder. The AASM strongly recommends against using actigraphy in place of muscle-activity recording for this diagnosis 1.
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It may miss quiet wakefulness. Reading, resting, or lying awake without moving can be classified as sleep.
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It may count movement during sleep as wake. The device detects activity, not conscious awareness.
These limits are why actigraphy results should not be read as a pass-or-fail test or used alone to name a disorder.
How accurate is actigraphy?
Actigraphy is generally better at recognizing sleep than wakefulness. In a meta-analysis of 96 studies involving 4,134 adults, actigraphy detected sleep intervals reasonably well but identified only about half of the intervals that polysomnography scored as wake 3.
Across the studies, actigraphy overestimated total sleep time by about 18 minutes and sleep efficiency by nearly 4 percentage points on average. It underestimated the time to fall asleep by about 7 minutes and wake time during the night by about 13 minutes. Differences were generally larger in adults with chronic health conditions, and results varied substantially between studies 3.
Those averages do not predict the error in one person's report. Accuracy changes with the device, algorithm, sensitivity setting, sleep disorder, age, and amount of quiet wakefulness. The useful question is whether the pattern is reliable enough to inform the specific clinical decision, not whether actigraphy is universally “accurate.”
What to expect during an actigraphy test
The exact instructions depend on why the test was ordered. The AASM guideline describes a general recording range of at least 72 hours and up to 14 consecutive days, while some questions need longer monitoring 1.
Your clinic will usually ask you to:
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Wear the device as instructed. Keep it on through normal daytime and nighttime activity unless the clinic tells you to remove it.
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Follow your usual schedule. The goal is normally to record real life, not to create an unusually “good” week of sleep.
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Complete the diary each day. Record attempts to sleep, final wake times, naps, medication or sleep-aid use, and anything unusual.
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Use the event button if provided. Press it at the times specified by your clinic.
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Record removals and problems. Note when the device came off, why it was removed, and when you put it back on.
Follow the device-specific instructions for showering, swimming, charging, and skin care. Do not assume it is waterproof. Contact the clinic rather than guessing if the device stops working or causes a persistent rash. Minor skin irritation is a possible harm, but the test is otherwise noninvasive 1.
How results are interpreted
There is no single “normal actigraphy score.” A bedtime that is appropriate for a night-shift worker may look unusual for someone who works mornings, and an occasional awakening does not automatically indicate a disorder.
A clinician looks for patterns that answer the referral question. They may compare workdays with free days, look for enough sleep before an MSLT, assess whether sleep timing matches a suspected circadian disorder, or compare the record with your diary. Symptoms and daytime functioning still matter.
If the device and diary disagree, that is not proof that either one is false. The difference may reflect quiet wakefulness, forgotten diary entries, an algorithm error, or a genuine gap between perceived and movement-estimated sleep. The clinician decides whether another test, such as polysomnography, is needed.
Actigraphy vs. other sleep-tracking methods
| Method | What it contributes | Main limit |
|---|---|---|
| Clinical actigraphy | Multi-day estimates of sleep timing, duration, and variability in everyday life | Infers sleep from movement and often misses quiet wakefulness |
| Sleep diary | Records when you intended to sleep and how you experienced the night | Depends on memory and perception |
| Polysomnography | Measures sleep stages, breathing, oxygen, heart rhythm, and muscle activity during a monitored sleep period | Usually covers one night and is more involved |
| Consumer wearable | May help you notice personal routines and share trends with a clinician | Device algorithms and validation vary, so it is not automatically a clinical actigraph |
A watch shape does not make a consumer tracker equivalent to prescribed actigraphy. The AASM guideline applies to clinical-grade devices, not ordinary consumer wearables. AASM guidance says consumer technology intended to diagnose or treat a disorder needs appropriate validation and regulatory clearance and should not replace a medical evaluation 4.
Frequently asked questions
Does actigraphy record sound, video, or my location?
Standard clinical actigraphy is based on movement, and some devices also record light. Features vary, so ask the clinic exactly what your assigned device collects. Do not infer its sensors from a smartwatch that looks similar.
Can actigraphy tell whether I was awake but lying still?
Not reliably. Quiet wakefulness can be scored as sleep. Your diary and event button can add context, but they do not turn movement sensing into a direct measure of brain-defined sleep.
Can actigraphy diagnose sleep apnea?
No. It may be integrated into a home sleep apnea test to estimate sleep time, but the breathing and oxygen sensors in the apnea test provide the relevant diagnostic information 1.
How long will I wear the device?
Many studies last several days to two weeks. Monitoring before an MSLT is commonly two weeks, while evaluation for insufficient sleep may last two to three weeks or longer. Follow the period set by your clinic because duration depends on the clinical question 1 2.
Is actigraphy the same as a fitness tracker?
No. Both may contain accelerometers, but clinical actigraphy uses a selected device, placement, recording plan, and analysis process for a defined medical question. A consumer device may still provide useful context, but its sleep score is not interchangeable with a clinical report 4.
