How Does Fitness Band Track/Measure your Sleep?

By | August 7, 2019

I got up today morning with a slight vibration on my wrist from my fitness band and soon after that, I got a notification that I had slept a total of 7 hours. It made me think, have you ever wondered how does fitness tracker keep count of the number of hours you have slept and analyze your sleep? Upon spending some time over the web I found sleep tracking feature of fitness band make use of the sensor which measures the movement of the wrist while you sleep.

The fitness bands will track your sleep by measuring movement made by you throughout your sleep. An accelerometer embedded in the Fitness bands will track your movements in sleep and will sync these movements to Fitness band app installed on your device to convert these movements into sleep data such as deep sleep and light sleep. This method of tracking sleep is called as Actigraphy.

Whats is Actigraphy?

Actigraphy is tracking of the continuous activity or movement with the help of a little device known as actigraph. These devices are used in the medical field for research and observation of sleep patterns and habits.

Whereas actimetry sensors are used for clinical research purposes in actigraph devices which are more expensive, Fitness tracker’s ability to measure sleep often comes from sensors called accelerometers, which detect a wearer’s motion, along with the speed and direction of that motion. Fitness bands permit the 3 axis measuring system on the wearable fitness device to record all big and small movements made by the individual. if the fitness tracker has gyroscope built-in, gyroscope movement data will be fed to the app for the sleep analysis. 

Although skilled devices which integrate actimetry sensors are priced over $800, trendy fitness trackers also has ability to track your activity and provide a rough estimate of sleep within the price bracket of $100 to $300.

How does Fitness Band know You are Asleep?

The principle way Fitness band realize when you’re snoozing is through detecting body movements. Even though we switch positions and may jerk a little sometimes during our sleep, we’re a lot more still when we’re at sleep than when we’re awake. These body movements are a valuable marker for estimating if you are at rest or if you are awake.

Depending upon the sort of Fitness band you have, it will detect your body Movement through either actigraphy or accelerometry. However modern sleep trackers may use additional parameters to determine if you are asleep or awake.

Sound: Fitness trackers may also include a Microphone to listen to the ambient noise in the environment you sleep in to deliver a report on the quality of sleep.

Heart Rate: When you go to sleep your heart rate reduces, Heart rate monitors can be used to measure if you are asleep or awake. HRM can also be used in detailed REM sleep (Rapid Eye Movement sleep).

How accurately Fitness Trackers will Track your sleep?

Polysomnography (PSG) is known to be the most accurate type of sleep diagnostic study known to sleep researchers. The PSG test is carried out monitoring many body functions, such as the activity of the brain (EEG), movements of eye (EOG), activity of muscle (EMG), and rhythm of the heart (ECG), during sleep. Whereas Fitness bands track sleep based on movement made by you during sleep. 

Studies have found that most of the fitness tracker are not a very accurate way of determining the sleep pattern and since the data available for the sleep analysis has to heavily rely on the movement of the wrist and heart rate and sound monitors.

Study results have varied, but for the most part, the consensus is that actigraphy is generally accurate enough to track sleep in healthy adults with “normal” sleep patterns. Problems arise when your sleep is disrupted for instance, if you have a sleep disorder or you just have disrupted sleep regularly. The more disrupted your sleep, the less accurate actigraphy will be at tracking it also there is no way a fitness tracker can distinguish between regular sleep and deep sleep.

Should you buy it?

Fitness trackers can provide a near to approximate value for the quantity of sleep but when it comes to the quality of the sleep fitness trackers doesn’t provide the complete picture.

Depending upon the results of the accuracy of the fitness trackers it is acceptable to rely on it for the quantity of sleep if you are healthy adult with normal sleep. But when it comes to detecting sleep disorders fitness tracker which use actigraphy is not reliable.

If you are the kind of person who benefits from knowing you are meeting the goals of your sleep and keep day to day track of your physical activity fitness trackers are worth it.