Actigraphy
The actigraphy is a noninvasive method to study human activity and resting cycles. Over a longer period of time, data on the movements of a test person and, in some cases, additional parameters such as brightness and ambient temperature are recorded and evaluated. The method is used in sleep medicine and sleep research .
The measuring device, known as an actigraph or actometer , is similar to a wristwatch, is worn on the wrist and has little influence on the behavior of the test person during the measurement period. During the measurement, the movements of a subject over a period of two to four weeks are documented at fixed time intervals (typically one minute). In the evaluation, it is possible, indirectly and yet quite reliably , to identify the duration of sleep and sleep-wake rhythm of the examined person, since the lower frequency of movements during sleep compared to the waking state allows conclusions to be drawn about the time and duration of sleep.
The method is reliable and valid for detecting sleep in normal, healthy populations, but is less reliable for detecting sleep disorders .
Measurement in actigraphy
Actigraphy is used to estimate the duration of sleep and the time of falling asleep and waking up, but only the recorded movement of an extremity for the respective epoch and, depending on the device, other data such as brightness and temperatures are recorded. This additional information also serves to support the evaluating algorithms.
Even if the devices are highly sensitive and the algorithms are sophisticated, what is generally defined under sleep (see sleep stages , REM sleep and non-REM sleep ) and is recorded by electroencephalography is not measured. Nor is it recorded what constitutes the subjective experience of sleep and is entered in sleep diaries and questionnaires by test persons.
Many subjects are inactive and awake for a while before the electroencephalographically defined sleep. Actigraphy tends to underestimate sleep latency. Studies show that written records of one's own sleep time regularly overestimate it. On the other hand, insomnia patients often significantly underestimate the length of their sleep in their records.
The actigraphy shows a sleep pattern in the sense of a circadian pattern of sleep and wakefulness over several sleep cycles.
Use in sleep medicine
In sleep medicine the actigraphy is an aid in the study of chronic sleep-wake rhythm disorders , parasomnias , sleep-related movement disorders and insomnia .
It is often used in addition to a sleep diary kept individually by the test persons to supplement and objectify the recording of sleep-wake times.
The differentiation in terms of sleep sleep stages or Aufwachstörungen is not possible and respect waking hours in bed it comes to greater inaccuracy. There are no uniform standards for the evaluation of actigraphy and situations such as putting down the device while showering or less movements in front of the television or driving a car must be taken into account. Actigraphy can reveal behavior-related lack of sleep.
Use in sleep research
Actigraphy is also used in sleep research. The collection of the resulting data does not take place locally and is possible in the familiar surroundings of the test subjects. The evaluation is computer-aided and requires little personnel and is therefore inexpensive. The examination of larger groups and examinations over a longer period of time are also feasible with reasonable effort. As long as the parameters to be recorded and the achievable accuracy are sufficient for the respective question, the environment of a sleep laboratory can be dispensed with.
This also enables investigations that would otherwise fail due to the costs. One example was a comparative study of different sleep parameters for sleeping in a hammock as opposed to sleeping in bed. From a sleep-medical point of view, a small group of middle-aged schoolchildren of 18 years of age without chronic sleep disorders was examined using actigraphy, whereby no significant difference was found between sleep in a hammock and sleep in a conventional bed.
Individual evidence
- ↑ a b Michael Littner, Clete A. Kushida et al .: Practice Parameters for the Role of Actigraphy in the Study of Sleep and Circadian Rhythms: An Update for 2002 . In: Sleep . tape 26 , no. 3 , 2003, p. 337-341 , PMID 12749556 (English).
- ↑ Timothy Morgenthaler et al., Standards of Practice Committee, American Academy of Sleep Medicine: Practice Parameters for the Use of Actigraphy in the Assessment of Sleep and Sleep Disorders: An Update for 2007 . In: Sleep . tape 30 , no. 4 , 2007, p. 519-529 , PMID 17520797 (English).
- ↑ S3 guideline for non-restful sleep / sleep disorders of the German Society for Sleep Research and Sleep Medicine (DGSM). In: AWMF online (as of 2009).
- ↑ Henrik Hein, Jana Abt, Holger Hein: Sleep in a hammock compared to sleep in bed . In: Somnology . tape 16 , no. 4 , 2012, p. 271-274 , doi : 10.1007 / s11818-012-0578-5 .
