Counting Sand Dust

Counting Sand Dust
Photo by Madhu Shesharam / Unsplash
"All intelligent beings spend one-third of their lives living within The Dreaming, entering my realm every night when they go to sleep..." Morpheus in the Sandman

I'm going to guess that you probably feel "slightly offended" by Morpheus' words, and not because you don't frequent his realm as much as he (or you) would like...

But this is not a post about the importance of sleep (here's one for that), this post is about how to interpret and use the sleep data gathered by your Smartwatch or SmartBand.

Wearables & Sleep

Modern SmartWatches and SmartBands track sleep metrics by using algorithms that analyse your Heart Rate and movement data to estimate sleep duration & quality.

Sure, these are no medical grade devices, and are not as accurate as one, but for us mere mortals the quality and depth of information obtained from these devices is more than enough to understand where we are at, and see improvements when we try so (if we are so inclined).

Wearable Sleep Quantity & Quality Metrics

Most wearables will provide you with information about your Sleep Duration and Sleep Quality.

Sleep duration needs no explanation, Sleep Quality metrics are another history...

The typical wearable will provide you with information about the different stages of sleep, how long you spend on them, and your nightly sleep patterns. Looking at the details you will faced with names like Light Sleep, Deep Sleep, Awake Time & REM (and no, that's not the band). Most, will also provide you with a sleep quality score or indicator, see example from Xiaomi's app below:


Let's quickly go through the Sleep Quality metrics normally found on your wearable's app:

Light Sleep

Is understood as a sleep stage where you are easily awaken, you are still moving a bit and your heart rate is still close to your waking resting heart rate.

Deep Sleep

Is when your heart rate drops down, you start moving less and is harder to be awaken.

Rapid-Eye Movement (a.k.a. REM)

Detected by your wearable when there is no perceptible movement but your heart rate has increased to closer to your resting heart rate (and your eyes are moving like you are watching pin-ball in perpetual motion).

Sleep quality score or indicator

Is a way to put together all variables and giving you and indication if your sleep quality & quantity are close to the recommendations. Not scientifically valid but can be used as an indicator of where you are, and can be an easy way of tracking if you are going in the right direction.

Awake Time

Duh! The neighbours dog did it again!

All this said, be aware that the way wearables generally describes sleep is a bit different to the way the latest science describes it (material for another post). for now lets keep to how you can use the data we get.

Don't Sleep on Recommendations

The recommendations for sleep duration are quite simple: 7-9 hours per night. Now, if you believe that's 7-9 hours of wasted time, then I invite you to read this post.

As you probably have grasped by now, Sleep Quality is a bit of a beast to define, and scientists are still trying to figure-out the shape of the beast. What is now clear is that quality is at least as important as quantity, and definitely more important if the quality is rubbish!

New research is linking deficiencies in the different sleep quality metrics, from not enough deep sleep, to lack of REM, to issues with memory & cognitive performance, metabolic issues, inflammation, etc... all pretty bad stuff...

The good news is that scientist are also beginning to understand the patterns of good quality sleep.

Sleep Metrics vs Recommendations

Looking at the recommendations, the Science of Sleep, and the sleep metrics available on modern wearables you should be aiming at:

  • Sleeping between 7-9 hours per night;
  • Achieving 3-4 full sleep cycles of 90 minutes each, with each including both Light & Deep Sleep.
  • Falling into Deep Sleep or a REM within the 1st 90 minutes;
  • Experience longer REM periods as sleep progresses;
  • Little or no Awake time (not impacting the 7-9h sleep recommended);
  • Quickly falling into sleep if awaken (max 20 min).

The value of Subjectivity

Generally speaking sleep quality is one of those that is easier felt than described, the list above will help you gage the quality of sleep in factual terms, and if it is improving, but, in the end, you will know if you had a good "shuteye", or not!

Trying to define how something feels is never easy, but here goes some characteristic of good sleep:

  • Falling asleep within 30 minutes, or less, of going to bed;
  • Sleeping throughout the night, or waking up no more than once per night;
  • Falling back asleep within 20 minutes of a nightly loo trip (or that sneaky trip to the fridge);
  • Feeling rested and energised in the morning.

How to spend more "Quality Time" with Morpheus

Here are some tips on how to make the Lord of The Dreaming happy, and feel great yourself:

  1. Prioritise sleep: sleep between 7-9h, but no longer than you need to feel rested;
  2. Consistent bed time, even at weekends;
  3. Be serious about sleep hygiene: optimise your bedroom for sleep, invest in  good and comfortable mattress, pillows & bedding (best you can afford), minimise exposure to bright lights, and ingestion of caffein & alcohol 2-3h before sleep, and ensure you mentally unwind before bedtime (you won't sleep if your brain is switched to max).

At Kognitas we know Sleep is foundational for good health and incentivise you to spend a good amount of quality time with Lord Morpheus. If you would like to start improving your sleep, your way and at your own pace join Kognitas today!


  1. Modern SmartWatches and SmartBands track sleep metrics by using algorithms that analyse your Heart Rate and movement data to estimate sleep duration & quality;
  2. Wearables are not as accurate as medical grade sensors but provide enough data to measure sleep quality & duration, detect areas for improving, and track progress;
  3. Adults are recommended to sleep between 7-9 hours per night;
  4. Sleep quality is more difficult to define but sleep stages duration & frequency can be used to determine it, but, ultimately each of us know if we had a good night's sleep;
  5. General recommendations to a good trip to The Dreaming: Prioritise sleep, Consistent bed time & Be serious about sleep hygiene.


  1. What is a Wearable Fitness Tracker? | link
  2. Analyzing Sleep with Wearables | link
  3. Do Sleep Trackers Really Work? | link
  4. Are sleep trackers accurate? Here’s what researchers currently know | link
  5. National Sleep Foundation's sleep time duration recommendations: methodology and results summary | link
  6. Brain Basics: Understanding Sleep | link
  7. Sleep Basics | link
  8. The 4 Stages of Sleep | link
  9. The 4 Stages Of Sleep — Cycles, Phases, and Improvement | link
  10. How To Determine Poor Sleep Quality | link
  11. What Is Sleep Quality? | link
  12. Sleep quality: An evolutionary concept analysis | link