Actigraphy

Actigraphy is a method of activity and sleep study achieved by mounting a small actigraph unit on a patient for an extended period of time. The unit itself typically includes a small accelerometer and continually records the movements it undergoes. When the data is later read to a computer it can be analysed and used in the study of circadian rhythm and wake-sleep patterns.

It usually involves subjects to wear an actigraph to measure gross motor activity. Motor activity usually under test is that of the wrist, measured by an actigraph in a wrist-watch-like package. Actigraphs measure day-to-day activity of an individual, recording movement being made during waking and sleeping hours.

Actigraphy is useful for assessing daytime sleepiness in situations where a laboratory sleep latency test is not appropriate. Actigraphy is used to clinically evaluate insomnia, circadian rhythm sleep disorders, excessive sleepiness and restless leg syndrome. It is also used in the assessing of the effectiveness of pharmacologic, behavioural, phototherapeutic or chronotherapeutic treatments for these disorders.

Actigraphy has not traditionally been used in routine diagnosis of sleep disorders but is increasingly being employed in sleep clinics to replace full polysomnography. The technique is much more extensively used in academic research and is being increasingly employed in new drug clinical trials where sleep quality is seen as a good indicator of quality of life.

Models of Actigraphs vary widely in size and features and can be expanded to include sensors which monitor light, sound, temperature, parkinsonian tremor, allow for subjective user input or which allow for the recording of a full EEG data stream.