Actigraphy

Actigraphy is a method of estimating sleep and wake patterns over days or weeks by recording body movement with a small wrist-worn sensor.

The device contains an accelerometer that samples motion continuously; software then applies validated algorithms that classify still periods as sleep and active periods as wake. From that record, clinicians derive estimates of bedtime, sleep onset latency, total sleep time, wake after sleep onset, sleep efficiency and the regularity of the sleep-wake rhythm. Because it is worn at home during ordinary life, actigraphy captures habits that a single night in a sleep laboratory cannot, and it is especially useful for insomnia, circadian rhythm disorders, shift work and checking whether a person is getting enough sleep before a daytime sleepiness test.

Its limits are important: it cannot identify sleep stages such as REM or deep sleep, it tends to overestimate sleep in people who lie still while awake, and it does not measure breathing, so it cannot diagnose sleep apnea. Polysomnography remains the reference standard for those questions. Consumer fitness trackers use similar sensors but their algorithms are generally not validated for clinical use. In cannabinoid sleep research, actigraphy is a common objective outcome alongside questionnaires such as the ISI and PSQI; studies using it have been small and short, and no cannabinoid has an approved use for any sleep disorder.