aktigraphy

Aktigraphy is a non-invasive method for monitoring human rest-activity cycles using a motion sensor, typically worn on the wrist. The device records objective movement data (accelerometer counts) over time, which are translated into activity levels by software. By applying validated algorithms, actigraphy estimates sleep parameters and circadian patterns outside a laboratory setting.

Common outputs include total sleep time, sleep onset latency, wake after sleep onset, and sleep efficiency. In addition, activity rhythm measures such as interdaily stability and intradaily variability describe the regularity and fragmentation of daily patterns, while circadian phase estimates (such as acrophase) provide a sense of peak activity timing. Epoch lengths commonly range from 30 to 60 seconds.

Data collection usually spans several days to weeks, enabling assessment of habitual sleep and rhythms. Sleep diaries or event markers may be used to improve interpretation and to help identify periods of non-wear or atypical activity.

Validation and limitations: actigraphy has been validated against polysomnography for many populations, making it useful for estimating sleep in real-world settings. However, it cannot measure sleep stages and may misclassify quiet wakefulness as sleep or movement as wake, depending on the algorithm, epoch length, and device. Compliance and device wear issues, as well as differences between commercial and research-grade devices, can affect accuracy and comparability.

Applications include clinical sleep medicine, circadian rhythm research, pediatrics, geriatrics, and occupational health, where long-term, home-based monitoring informs diagnosis, treatment evaluation, and understanding of daily activity patterns.