Actigraphy

The Actigraphy is a noninvasive method to study human activity and rest cycles. Over a longer period data on the movements of a subject and some additional parameters such as brightness and ambient temperature are recorded and evaluated. The process is in sleep medicine and sleep research to application.

Referred to as actigraph or actometer measuring device itself resembles a wristwatch is also so worn on the wrist and has little influence on the behavior of the subjects during the measurement period. In the measurement at fixed time intervals ( typically one minute ) documented the movements of a subject over a period of two to four weeks. In the analysis it is possible to indirectly and quite reliably detect sleep duration and sleep-wake rhythm of the person examined as the lower incidence of movements during sleep compared with the waking state to draw conclusions about sleep and sleep duration.

The method is reliable and valid for the detection of sleep in normal healthy populations, but less reliable in detecting sleep disorders.

Measurement in the actigraphy

The actigraphy is what is used to estimate the duration of sleep and the time of falling asleep and waking up, but is retained in the recording only the detected movement of a limb of the respective age and depending on the device additional information, such as brightness and temperatures. These additional data are also used to support the evaluating algorithms.

Even though the devices for highly sensitive and sophisticated algorithms are not being measured, which is generally defined under sleep (see Sleep stage, non-REM sleep and non-REM sleep) and detected by the electroencephalography is. It is not recorded what constitutes the subjective experience of sleep and is entered in sleep diaries and questionnaires of subjects.

Many volunteers have a while before going to sleep electroencephalographic defined inactive and awake. The actigraphy tends to underestimate the sleep onset. Studies show that a written record of their own sleep duration overestimate them regularly. On the other hand, underestimate insomnia patients, the duration of sleep in their own records often considerable.

The actigraphy shows the result of a sleep pattern in terms of a circadian pattern of sleep and wakefulness across multiple sleep cycles.

Use in sleep medicine

In the actigraphy in sleep medicine is an aid in the study of chronic sleep-wake rhythm disorders, parasomnias, sleep-related movement disorders and insomnia.

It is often used next to one of the subjects individually managed sleep diary to complement and objectification in the detection of sleep-wake times.

The differentiation of sleep regarding sleep stages or Aufwachstörungen is not possible and with respect to the time awake in bed, there is greater uncertainty. Standards for evaluation of actigraphy does not exist and in the evaluation have situations such as the dropping of the appliance in the shower or fewer movements in front of the TV or while driving are considered. The actigraphy can show behavioral sleep deprivation.

Use in sleep research

Even in sleep research that actigraphy is employed. The levying of the data takes place not bound and is possible in the familiar environment of the subjects. The evaluation is performed with computer assistance and little is labor intensive and therefore cost. The investigation of larger groups and studies over a longer period are feasible with reasonable effort. As far as the parameters to be measured and the achievable accuracy for the problem in hand sufficient can thus be dispensed with the environment of a sleep laboratory.

It also studies are possible that would otherwise fail because of the costs. One example was a comparative study regarding various sleep parameters for sleep in a hammock in contrast to sleep in bed. After sleeping a medical point of a small group of students in middle age of 18 years was examined without chronic insomnia using actigraphy to, with no significant difference between the sleep in the hammock and sleep has been found in a conventional bed in the result.