Actimeter: definition, operation, benefit for sleep

2024-03-02 09:54:25

« The most obvious indicator of sleep is immobility », recalls an article from the French Society for Sleep Research and Medicine (SFRMS) (source 1). And even if the latter is not absolute, “the detection of this relative immobility therefore constitutes a good indicator of sleep”.

Actimetry is a medical technology ” which serves to record motor symptoms, such as abnormal uncontrolled movements (dyskinesia), tremors, slowness,” explains the Toulouse University Hospital (source 2). This is why it is often used in patients who have Parkinson’s, in order to better monitor their disease. But it is also used in sleep medicine.

What is an activity meter used for?

The activity meter is used to determine the rest/activity rhythm of a subject which gives indications on the sleep/wake rhythm of this subject over periods of several days. Indeed, to sleep better, it can be useful to better understand our biological clock. This is what the activity meter is for: record our sleep data and analyze the information via a computer or smartphone. Purpose ? Use the information collected to improve our sleep.

An accelerometer that measures movements during sleep

The activity meter contains an accelerometer, i.e. a sensor that records the number of movements and their intensity. However, when you sleep deeply, you are perfectly still because of a phenomenon of muscular inhibition, explains Claude Gronfier, researcher in chonobiology.

These devices can therefore highlight very restless and unrefreshing sleep.

What does an activity monitor look like?

The activity monitor has a recording system in a small box usually worn on the wrist of the non-dominant hand. It exists in the form of a watch, bracelet or even connected sensors, indicates the Toulouse University Hospital. Some models require you to start recording, others do it automatically.

« The choice of activity meter will be oriented by the size and weight of the recorder (they are the size of a large watch), any associated functions (light detection, temperature detection, etc.) and software for configuring the recorder and data analysis,” explains the SFRMS.

But activity meters all have in common: the use of a piezoelectric type sensor which makes it possible to detect accelerations linked to movements”.

How does an activity meter work?

The device is generally worn eight to fifteen consecutive nights to produce an accurate picture of sleep. It can be combined with a sleep diary. “Disorders of sleep-wake rhythm (phase advance or delay, irregular rhythms) are very well objectivized by actimetric recording on 1 to 3 weeks », Reports the SFRMS.

Data is transmitted to a computer or smartphone via wifi or bluetooth. The software that accompanies the activity meter transforms the information into curves. Deep sleep episodes result in a flat curve.

The activity meter captures body movements and micro-awakenings which occur during light sleep phases: these are the peaks of the curve.

What are the disadvantages of the activity monitor?

The only problem with this non-invasive technique: the quality of the sensors. It is not always sufficient and the calculation of sleep cycles is therefore imprecise.

Actimetry: what are the results used for?

In case of sleep problems, these recordings may be useful to a specialist. The data saved in the computer or smartphone is transmitted, in the form of an actogram (graph) which will give access to information on the quality of your sleep and its organization over 24 hours.

The results will allow in particular, indicates an article published in the journal Sleep medicine (source 3) :

Of determine the degree of phase shift in getting up and/or going to bed time compared to usual times of everyday life; To determine the irregularity of the number of episodes of the number of wakefulness or sleep for 24 hours; objectively measure the rest/activity cycle over very long periods.