Actigraphy is a non-invasive method of monitoring human rest/activity cycles. A small actigraph unit, also called an actimetry sensor,is worn by a patient to measure gross motor activity. Motor activity often under test is that of the wrist, measured by an actigraph in a wrist-watch-like package. The unit continually records the movements it undergoes. The data can be later read to a computer and analysed offline. In some applications, such as the Smart OneHealth Band the data is transmitted and analysed using the software.
Sleep actigraphs are generally watch-shaped and worn on the wrist of the non-dominant arm. They are useful for determining sleep patterns and circadian rhythms and may be worn for several weeks at a time.
Contrary to polysomnography, the patient remains movable and does not necessarily need to be located in a laboratory while the required data is being recorded. This permits the patient to stay in his or her natural sleep environment which may render the measured data more generally applicable. Sleep actigraphs are also more affordable than performing a polysomnography and can therefore be advantageous as well, particularly when conducting large field tests.
Actigraphy is useful for assessing daytime sleepiness in situations where a laboratory sleep latency test is not appropriate. It is used to clinically evaluate insomnia, circadian rhythm sleep disorders, excessive sleepiness and restless legs syndrome. It is also used in assessing the effectiveness of pharmacologic, behavioural, phototherapeutic or chronotherapeutic treatments for such disorders.
Actigraphy has been actively used in sleep-related studies since the early 1990s. However, it has not traditionally been used in routine diagnosis of sleep disorders but is increasingly being employed in sleep clinics to replace full polysomnography.
The main reason for this development is the fact that, while retaining mobility, actigraphy offers reliable results with an accuracy that is close to those of polysomnography (above 90%).
The technique is 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.