Actigraphy: The Wrist Sleep Test Worn at Home

Actigraphy is a sleep test you do at home with a small device worn on the wrist like a watch. It records your movement day and night, usually for several days up to two weeks, while you keep a sleep diary.^[1] Sleep doctors use it to see your real sleep schedule, especially for insomnia, body clock problems and before daytime nap testing.

What an actigraph is and how it works

An actigraph is a small, light device with a motion sensor inside. Most are worn on the wrist of your non-dominant arm. Some also have a light sensor and an event button you press when you get into bed or get up.

• Movement — the device counts how much you move, minute by minute.
• Software — long stretches of stillness are scored as likely sleep, and activity as likely wake.
• Sleep diary — your notes on bedtimes, wake times, naps and times the device was off help the sleep specialist read the data correctly.

What to expect while you wear it

• Wear it all the time — day and night, from at least 72 hours up to 14 days, as your sleep clinic directs.^[1]
• Keep your normal routine — the goal is to see your usual sleep, not your best sleep.
• Fill in the diary daily — write down bedtimes, wake times, naps, and when you took the device off.
• Return the device — the data is downloaded and reviewed by a sleep specialist.

What actigraphy estimates

• Sleep and wake times — about when you fall asleep and when you wake up each day.
• Total sleep time — how much you sleep across the day and night, including naps.
• Time awake in the night — how long you are awake after first falling asleep.
• Your rhythm over time — whether your schedule is regular, shifted late or early, or scattered across the day.

These are estimates. Actigraphy cannot see brain waves, so it cannot tell sleep stages apart. But because it runs for many days instead of one night, it can show patterns a single overnight test would miss, such as sleeping in on weekends or long naps during the day.

When sleep doctors use actigraphy

A 2018 American Academy of Sleep Medicine (AASM) guideline suggests actigraphy for these uses, in adults and children where noted:^[1]

• Insomnia — to measure sleep in adults and to help assess children and teens. It can guide treatment such as CBT-I.
• Circadian rhythm disorders — in adults and children, to show a body clock that runs late, early or irregular. See circadian rhythm sleep disorders.
• Before an MSLT — to check that you slept enough in the weeks before a Multiple Sleep Latency Test for narcolepsy or other causes of heavy sleepiness. AASM guidance for adults recommends a sleep diary, with actigraphy when available, for two weeks before the test.^[2]
• Not enough sleep — to estimate total sleep time in adults who may simply be sleeping too little.
• With a home sleep apnea test — some home tests include an activity sensor to estimate how long you slept during the test.

Actigraphy is especially useful for children and some teens, who may not be able to keep an accurate sleep diary. The guideline's suggestions for children also cover children with developmental disorders.^[1]

Limits compared with an in-lab sleep study

An overnight in-lab sleep study, or polysomnography (PSG), records brain waves, breathing, oxygen, heart rhythm and leg movements. Actigraphy records only movement, but over many days at home.

• Lying still awake can look like sleep — so actigraphy may miss some time awake in bed.
• No breathing data — it cannot diagnose sleep apnea on its own.
• Not for leg movement disorders — the AASM recommends against using actigraphy in place of sensors on the legs to diagnose periodic limb movement disorder.^[1]
• Not a substitute for PSG — when an in-lab study is needed, actigraphy does not replace it.^[1]

Learn what happens during a full study in what happens during a sleep study.

Actigraphy vs. a consumer smartwatch

Smartwatches and rings use similar motion sensors, and some track sleep fairly well.^[3] The difference is in how the data is collected and used:

• Medical device — the AASM guideline applies only to FDA-cleared actigraphs, not consumer wearables.^[1]
• Set protocol — a clinical actigraph is worn on a planned schedule with a sleep diary.
• Expert review — a sleep specialist reads the raw pattern, not just an app score.
• Wellness vs. testing — most consumer sleep features are not meant to diagnose sleep problems.^[4]

Some watches now have FDA-authorized sleep apnea alerts. Read about them in can a smartwatch detect sleep apnea.

When to see a sleep specialist

• You can't fall asleep or stay asleep — most nights, for weeks, and it affects your day.
• Your body clock feels off — you can't fall asleep until very late, or you wake much earlier than you want.
• You are very sleepy in the day — even after what seems like enough sleep.
• Your child's sleep schedule is a struggle — trouble falling asleep, frequent night waking, or a teen who can't get up for school.

Sleep care in Cedar Park

Dr. Minal Patel is board-certified in pediatrics and sleep medicine. Our practice cares for insomnia (including CBT-I), narcolepsy and MSLT testing, and sleep problems in children and adults, and offers in-lab and home sleep studies. We are accepting new patients. Office hours are Monday through Friday, 8:30 to 5:00. We accept Medicaid and CHIP for sleep patients. We do not take walk-ins.