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Many wearable devices now have sleep monitoring functions, and clinics often encounter parents who bring in recorded data on apps for consultation. However, can these devices really be applied to children? Or which of the recorded values are reliable? Which are unreliable? This really requires more research to confirm. Today we will introduce the longest-used wearable device in sleep medicine: the actiwatch (activity tracker).
Appearance and Principle
The appearance of the actiwatch may vary slightly depending on the manufacturer, but it generally looks like a watch. Brands with more functions may have a larger size and more buttons, but comfort will be compromised when worn (Note 1).
Inside the activity tracker are an activity recorder and a light sensor, which evaluate the intensity of activity and the strength of received light at regular intervals (Note 2). Therefore, in theory, during sleep at night, both activity and light should decrease. When they fall below the set threshold, the analysis software will determine that this time point is in a sleep state, and the doctor/technician can refer to the sleep diary for further adjustment.
When to Use
Because the activity tracker can record long-term activity status, it is often used clinically in the following two situations:
To understand the day-night cycle changes: late sleep and late waking? Early sleep and early waking? Or an irregular schedule?
In attempting to identify the cause of "feeling very sleepy during the day", such as narcolepsy/hypersomnia, which is characterized by long total sleep time, or sleep deprivation syndrome, which finds that the total sleep time at night is reduced.
Difference from Sleep Diary
If the sleep diary written by the parent/patient has a high level of credibility, there is no need for additional testing.
However, sometimes the child is lying in bed with their eyes closed, and the parent may think they are asleep. Or the child may already be awake and playing, but the parent may not know because they are in a different bed (room) or the parent is still asleep, which can lead to an incorrect estimation of the child's sleep duration. In this case, the activity tracker can evaluate whether the activity level at that time point is below the threshold, which provides a more objective evaluation.
Or if a teenager gets up to play on their phone in the middle of the night, they may not want to write it in their sleep diary! In this case, the activity tracker has a light sensor, which can detect changes in light and know that the child is not actually sleeping.
Difference from Polysomnography (PSG)
The two tests diagnose different diseases! Polysomnography mainly targets respiratory/movement disorders, such as sleep apnea syndrome, periodic limb movement disorder, etc.
It is important to note that while actiwatch can provide some information about a person's awake-sleep patterns, they can not provide more information as a full polysomnography test. Therefore, if a person has suspected sleep disorders, they should seek professional medical advice and undergo a full sleep study.
What can you see on an activity tracker?
Different brands of activity trackers may display different numbers, but they generally include the following: Bedtime ,Wake-up time ,Time spent in bed, Total sleep time ,Sleep latency (time it takes to fall asleep), Sleep efficiency, Wake after sleep onset (duration and frequency of awakenings)
The software will calculate the daily values and the average values during the time the tracker is worn. However, it is important to note that the tracker cannot tell you why you are not sleeping well, like a polysomnography (PSG) test can.
Although some models are waterproof, it is recommended to remove the tracker during activities such as bathing or swimming to avoid damage.
Wear the tracker on your non-dominant hand; sometimes it can also be worn on a baby's ankle.
Try to avoid clothing covering the tracker during normal activity, as the light sensor may be blocked and mistakenly interpreted as sleep.
It is important to keep a simple record of your activity, including bedtime, wake-up time, and times when the tracker was not worn, to help doctors analyze the results accurately.
Lastly, do not lose or damage the device as most hospitals require users to sign a disclaimer for any potential damage to the device.
Actiwataches are a useful tool for monitoring daily activity levels and sleep patterns in certain situations, such as identifying changes in sleep-wake cycles or investigating excessive daytime sleepiness. However, their accuracy and reliability may vary, and they should not be used as a substitute for professional medical advice and diagnosis.