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What Is Actigraphy?

Small Monitor Records Movement to Diagnose Circadian Rhythm Disorders, PLMS


Updated June 17, 2014

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

There are many potential ways to evaluate sleep, and one of the least intrusive, actigraphy monitoring, can be used to assess sleep at home with a device called an actigraph.

What Is Actigraphy?

Actigraphy is the continuous measurement of activity or movement with the use of a small device called an actigraph. With the push of a button, it may also have the ability to mark events such as bedtimes or waketimes.

What Does an Actigraph Look Like?

An actigraph is a small, wristwatch-sized device. It is lightweight and typically worn on a limb, such as at the wrist or ankle.

How Does It Work?

An actigraph monitors movement and can be used to assess sleep-wake cycles, or circadian rhythms, over an extended period of time. It uses something called an accelerometer to record motion. This information is then used to create a graph. Active times result in a peak (or bar) on the graph while quiet times, such as sleep, will be represented by a flat line.

Actigraphs may be worn for weeks or even months. Generally, it can record data for 24 hours per day for about two weeks. Common models can take measurements up to 32 times per second. They are useful to help determine whether disruptions in the sleep-wake cycle exist, as may occur in many different sleep disorders.

Which Sleep Disorders Can Be Assessed with Actigraphy?

There are many sleep disorders that may be better understood by completing actigraphy monitoring. These may include:

What Are the Limitations?

Aside from providing information about whether you are active or inactive, there is not much more that the devices can record. Furthermore, it isn’t very smart, so if you leave your actigraph sitting on your dresser, it may seem like you are sleeping for as long as it sits there. The memory may be limited, so it is necessary to download the information at regular intervals. In addition, often the results must be correlated with a sleep diary.

Formal sleep studies, called polysomnography, provide much more detailed assessments of your sleep, but the simplicity and availability of actigraphy may be an acceptable alternative in some situations. In some cases, it may be a good first step in learning about your sleep.

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