ACTIGRAPHY LIMITATIONS | SleepTech

Clinical Actigraphy Overview

Actigraphy involves continuous recording of movement, usually via a wrist-worn accelerometer, over several days or weeks. It is used in clinical sleep medicine primarily to evaluate circadian rhythm sleep-wake disorders (CRSWD) and to confirm sufficient sleep duration prior to an MSLT.

Methodological Constraints vs. PSG

Actigraphy algorithms infer sleep based on the *absence of movement*. Therefore, they are highly prone to:

• Overestimating Sleep Time (TST): In individuals who lie motionless awake in bed (common in chronic insomnia), actigraphy will incorrectly score this quiet wakefulness as sleep, inflating sleep efficiency metrics.
• Underestimating Sleep Time: Conversely, in conditions with high nocturnal motor activity (e.g., severe OSA, RLS/PLMD, or pediatric patients), actigraphy may incorrectly score restless sleep as wakefulness.
• Inability to Stage Sleep: Actigraphy cannot differentiate between N1, N2, N3, and REM sleep. It only provides a binary Sleep/Wake output.

Technical review of the capabilities and limitations of this methodology in clinical sleep medicine.