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Sleep Tracking – What You Need to Know

Author imageThe Mattress Warehouse

A couple of months ago I wrote a blog post where I asked the question whether I should track my sleep or not. In this blog post, I didn’t really take an in-depth look at the mechanics of sleep tracking. Instead, I discussed the basic idea behind tracking your sleep since my phone kept asking me when I was asleep. And believe it or not, since then (October last year) my smartphone hasn’t stopped asking me what times I was asleep!

I still haven’t given in though. My phone doesn’t know my sleep routine as of yet! As a rule, my sleep is restorative and I tend to wake up feeling refreshed. Thus I see no reason why I should tell the whole wide world when I was sleeping.

But You Can Track Your Sleep!

The fact that I don’t want to share my sleep patterns with the world doesn’t mean that you shouldn’t. Here are some reasons why you should track your sleep:

  • When you wake up feeling tired, day after day.
  • If you spend more than 7 hours in bed every night… And for some reason you still feel tired and drained when you get up in the mornings.
  • You toss and turn, but just can’t seem to fall asleep.
  • If tend to wake up a lot at night.
  • When you have a hectic weekly schedule and you go to bed at different times every night.

If you have a perfectly healthy sleep routine, sleep tracking is not necessarily for you. Unless, of course, you want to be able to tell other people why you feel so refreshed every day. On the other hand, if you spend enough time in bed but you stay tired, then I suggest you start tracking your sleep. Either in the form of keeping a sleep diary (discussed in my previous post on keeping track of your sleep). Or by smart device. A bit more on devices later on.

The Use of Sleep Tracking

Sleep tracking in the flesh.
Fitbit sleep tracking Android app interface.

So by now you should know whether sleep tracking is for you or not. Let’s assume that you fall into one of the above mentioned categories and you need to keep track of your nocturnal habits. You are probably wondering what good can come of it, right? Why do you need to go through all the rigmarole to keep track of when you are asleep?

Well, it is simple, really. If you can gather information about your apparently broken sleeping pattern, you can start to fix it. However, this is not a short term project. Most sleep experts agree that you need week’s if not months’ sleep data in order to properly identify what is wrong with your sleeping habits. So, if you wake up feeling exhausted and drained, start tracking your sleep tonight! Once you’ve built up a big enough database, you can take it to your doctor so that he/she can try to figure out why you’re not getting enough restorative sleep.

Be warned though, sleep tracking is not infallible. In other words, the data produced by your sleep tracker or sleep diary might be incorrect. Let’s take look at the different types of commercial sleep trackers out there.

  • Physical sleep diary – As you can see from the name, this is when you just write down when you go to bed and when you get up again.
  • Smartphone – You can download all sorts of sleep tracking of apps to your smartphone.
  • Smartwatch – Modern smartwatches can keep track of when you are awake or asleep.
  • Fitness tracker – A lot of wristband fitness trackers can monitor your sleep/wake cycle.
  • Smart bed – There are beds and bedding out there that can track your nighttime temperature and sleep habits.
  • Bedside sleep tracker – Put this on your nightstand to monitor heart rate, breathing and movement while you sleep.

How Do Sleep Trackers Work?

Sleep tracking - stages of sleep.
Tracking the different stages of sleep…

As you have seen, there is a variety of sleep tracking devices on the market. From the good ol’ handwritten diary, to a bed that gives you your sleep data. Obviously, most of these devices function on a different level. Moreover, some of them are more accurate than others. Some of these devices even claim to be able to tell you how much time you spent in each sleep stage every night! So, how does it work? How on earth does a watch or a phone map the time you spend in Dreamland? Let’s take a look!

Sleep Diary

The only way that a sleep diary can track your sleep is if you manually input the data. Every time before you switch off the light, jot down the time. Did you get up to go to the toilet? Jot down the time. Is it time to get out of bed? Jot down the time. Obviously, this method is tedious and it won’t give you any data on the time you spent in REM sleep.


Nowadays most smartphones come out with an accelerometer. This is a device that monitors your body movement. Do you have an app on your phone that counts the number of steps you take every day? That app is made possible because of the accelerometer. In order for you to properly track your sleep with your smartphone, it needs to be in bed with you.

Smartwatch/Fitness tracker

These watches and trackers also come with built-in accelerometers. They are quite a bit more effective than those in your phone (for sleep tracking purposes, anyhow). Seeing as the tracker/watch is coupled to your wrist, it will pick up movement a lot better than a phone can. And it also won’t pick up if your partner or pet moves around on the mattress at night, something that your phone might pick up.

More recent models of these trackers/watches also capture your heart rate, which improves the accuracy of the device.

Smart Beds

Smart beds have built-in movement sensors that monitor your movement. Some of them also measure your temperature. Having your regular sleeping temperatures at hand can be quite useful. Especially if you struggle to fall asleep or stay asleep. Nighttime temperatures play an important role in how well we sleep. If you are too warm or cold, the odds are that you won’t get enough deep sleep. So, with a smart bed that measures your temperature, you can easily make small adjustments to reach optimum sleeping temperatures.

Bedside Sleep Tracker

These sleep trackers do not make contact with your body at night, so some people believe that it can’t be as accurate as wrist-bound fitness trackers, for instance. However, some of these trackers have really cool extra’s! The ResMed S+ sleep sensor monitors noise levels, light intensity and ambient sound.

With this kind of information at your fingertips, you can quickly find solutions to possible sleeping problems. For instance, if your room is too light at night, it can hinder the quality of your sleep! If your sleep monitor tells you that it is too light, you can put up darker curtains and thus get a better night’s rest. The same goes for ambient sound and room temperature.

Is Sleep Tracking an Accurate Science?

Sleep tracking
Apparently smartwatches can’t be trusted when it comes to discerning between sleep stages.

There are mixed feelings about this question. Sure, some sleep trackers perform better than others. But do they give 100% accurate data? Unfortunately, it seems that they don’t. There is quite a bit of controversy about this matter in the scientific world. However, since the inception of wrist-bound sleep trackers, technology has improved dramatically. So not all of the critiques can be justified in 2019.

“Heart rate is not the same as brain waves. And brain waves tell us what stage of sleep we’re in.”

Dr. Lisa Meltzer, sleep researcher

Most sleep experts agree that smartphones, smart beds and smartwatches can track whether you are asleep or awake quite accurately. However, the science community is adamant about the fact that these devices cannot track the different stages of sleep that you may find yourself in. Sure, these modern trackers can monitor heart rate, but heart rate can’t tell you which stage of sleep you are in. The most scientific (and correct) way to determine sleep stages is through the use of Electroencephalography (EEG).

EEG monitors the transfer of electrical currents in the brain, i.e. brainwaves. Moreover, the most accurate way to determine sleep stages is through monitoring brainwave and eye activity. For instance, one can easily determine whether someone is undergoing REM sleep by looking at that person’s eyes. No smartphone or fitness tracker has that capability (shall I say… yet?).

Wrist Actigraphy and Accelerometry

Two different kinds of motion detectors, both bound to the wrist. Accelerometers are what you will find in most smartwatches and fitness trackers. Whereas actigraphy is a more scientific method of monitoring one’s sleeping patterns through attaching heart rate monitors and motion detectors to the wrist. Dr’s Jennifer L. Martin and Alex D Hakim proved in 2011 that monitoring sleeping patterns via actigraphy is quite useful. In their research paper they specify that it should’t take the place of more sophisticated sleep tests, but it is useful nontheless.

Even though wrist sleep trackers have been bashed by the science community in the recent past, more recent studies show that these devices are quite useful. A 2016 study compared the Jawbone UP fitness tracker to polysomnography (sleep monitoring). The researchers found that the Jawbone was quite accurate with detecting the onset of sleep. However, the fitness tracker was a bit unresponsive when it was supposed to detect waking up. Overall the study found that the fitness tracker overestimated total sleep time by up to 35 minutes per night.

The Verdict?

Apart from the sleep stage problem, most modern sleep tracking devices can give you valuable information about your sleep patterns. So if you struggle to sleep properly at night, give sleep tracking a go!

PS. My wife allowed me to use her sleep data. She clearly needs to sleep some more!

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