How do fitness trackers monitor your sleep?

How does sleep quality influence longevity, and how can tracking it help us to boost our longevity?

Researchers discovered that individuals with greater longevity had strict and constant sleep-wake schedules and maintained optimal levels of deep (slow-wave) sleep compared with to other adults [1]. 

What are fitness trackers?

fitness tracker is a device usually worn around the wrist or waist that keeps track of specific body parameters like heart rate and motion [2]. Several of the latest fitness trackers available on the market today link up to a smartphone or a laptop.

Most of them have three-axis accelerometers which allow these trackers to monitor how fast individuals move in any direction. This information is then processed with algorithms to analyse the movements.

A fitness tracker is a device usually worn around the wrist or waist and keeps track of specific body parameters like heart rate and motion [

The tracker software uses complex algorithms to sort the data received into helpful information which will make sense to the user. Through this, an individual can track heart rates, daily exercise and even sleep patterns. 

Trends are established based on the history of the individual’s data available. This information becomes available for viewing to help the user make more informed decisions about their fitness regimen.

Four stages of sleep

To better understand the process of how fitness trackers monitor sleep, first we need to get our heads around the four stages of sleep [3]:

  • Stage 1: short and only lasting between five and ten minutes, where sleep is shallow, and an individual can easily be woken up.
  • Stage 2: also known as light sleep, characterised by a slowing down of heart rate and breathing, which consists of about half of the time spent asleep.
  • Stage 3: the deep sleep stage, wherein the body relaxes, and your breathing rate and pulse drop further. This stage is beneficial and critical for growth and recovery, as well as for strengthening the immune system.
  • Stage 4: REM or the final stage, wherein the body is inactive, but the eyes move rapidly. Here, the heart rate increases, and breathing becomes more irregular. In addition, bodily functions like protein synthesis peak in this phase and when the individual is likely to dream.
To better understand the process of how fitness trackers monitor sleep, it would be helpful to include the four stages of sleep [3]:

What do these trackers monitor?

A vast assortment of sleep trackers are available in the market, with more releases coming out regularly [4]. Many are wearable trackers for your wrist, while others clip on your pillow or sit on your bedside table.

The features of these devices differ, but here are some common ones:

  • Environmental factors: some devices record environmental factors such as the temperature or amount of light in your room.
  • Lifestyle factors: other trackers cue you to enter details about actions that can affect sleep, like caffeine intake and food consumption. This also takes note of stress level information. Some devices are able to look into alcohol consumption and how it can affect sleep quality, as consuming alcohol is seen to have the single greatest negative impact on next-day recovery [5].
  • Sleep duration: by looking into the time you’re inactive, devices can note when you fall asleep at night and when you wake up in the morning.
  • Sleep phases: the tracking systems look at the stages of your sleep, and the time your alarm goes off within a period that you’re sleeping less deeply. In hypothesis, that makes it more manageable for you to awaken.
  • Sleep quality: these trackers can detect interrupted sleep, allowing you to know when you’re moving around or waking during the night.

Our recommendation:


Do sleep trackers improve sleep?

Currently, there is no definite information yet, as sleep is different for each individual. Although there are experts who believe tracking sleep could be doing more harm than good for some. 

For some who keep track of their sleeping patterns, it becomes a cause of unwarranted anxiety and worries. There’s even a name for it – orthosomnia, which describes people who obsess over the results of their sleep and fitness trackers. 

Choosing the right sleep tracker for you

Wearable sleep trackers are mainly fitness trackers and smartwatches that also track sleep [6]. There are also gadgets like rings and other devices for wearing on your head.

The non-wearable sleep trackers include smart beds, bedside monitors, smartphone apps and smart mattress pads. 

The primary consideration is whether you’ll feel comfortable wearing something while you sleep. Some people have no issue wearing a watch to bed, while others can’t stand it.

Do you need a fitness tracker to monitor sleep?

Sleep trackers can gather plenty of information about your sleeping habits, though there’s one crucial thing they commonly don’t do – they don’t measure sleep directly. Instead, they usually gauge inactivity as a surrogate for estimating sleep.

For precise data about your sleep habits, you’d have to do a medical sleep study, which observes brain waves to analyse the stages of sleep you cycle through during the night. These studies help diagnose disorders like sleep apnea and other sleep conditions.

Still, tracking devices can help recognise sleep patterns and give the user something to reflect on about their habits. If you’re an otherwise healthy person who wants to acquire some insight into your sleep routine, tracking devices might be a good option.

[1] https://bit.ly/3cdD9Qt
[2] https://bit.ly/3azJdlH
[3] https://www.techradar.com/news/how-does-sleep-tracking-work
[4] https://www.hopkinsmedicine.org/health/wellness-and-prevention/do-sleep-trackers-really-work
[5] https://www.whoop.com/thelocker/alcohol-affects-body-hrv-sleep/
[6] https://www.theverge.com/23013600/best-sleep-tracker-wearables

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The information included in this article is for informational purposes only. The purpose of this webpage is to promote broad consumer understanding and knowledge of various health topics. It is not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of your physician or other qualified health care provider with any questions you may have regarding a medical condition or treatment and before undertaking a new health care regimen, and never disregard professional medical advice or delay in seeking it because of something you have read on this website.