I’ve been fascinated by sleep tracking for a couple of years now. I’m a metric nerd, so if something can be quantified, I want to see it quantified. While I’ve been tracking my sleep for years, I’ve been testing and comparing three different trackers for the last several weeks. Here’s what I’ve learned.
Sleep tracking allows you to pinpoint the difference between a good night’s rest and a poor one. On a longer timeline, you can extrapolate the difference between the two—what you ate, what your stress levels were that day, and all the other little factors that can affect your sleep quality.
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To start, you might be wondering if you should track your sleep. Or why anyone would want to. Or if there’s even any value in doing so in the first place. And the simple answer is, well, not so simple. It depends on the person! You don’t need a gadget to tell you that you slept like crap. Likewise, you probably don’t need one that tells you when you’re well-rested either.
But that’s not what sleep trackers really do. They don’t tell you that you slept like crap—they tell you why you slept like crap. Or, well, they help you figure out why you slept like crap.
As with most things, it’s all in the details. You can learn a lot about yourself (and your body) by tracking your sleep. Rest and recovery are important for literally everyone—the more well-rested you are, the better you can perform at everything you do.
The devices I’ve been using range from very specific (Whoop) to general fitness use (Garmin) and the absolutely casual (Google Nest Hub 2nd Gen). These three devices should be able to cover what most people are looking for.
Before we really start to get into the weeds, however, I want to point out that my results are subjective. I’m not a doctor, no medical team performed any tests, and no one academically reviewed this data. This isn’t meant to be a scientific analysis of sleep data, nor should it be interpreted as such.
These are just my thoughts and experiences while using these devices. Your mileage may vary—and likely will. That said, I hope to shed some light on why you might want to track your sleep and offer some non-specific guidance on which device might work best for you.
Now that the table is set, it’s time for dinner.
I don’t consider sleep stats to be the be-all-end-all for how I’ll feel on a given day, but I’m always optimistically curious to see what each device spits out every morning. And while I’ve been tracking my sleep for years, this testing period has taught me that devices can differ wildly in their interpretations of your sleep cycles.
You’ll never get identical results from different devices. Or, in many cases, even similar results. Because sleep is weird, and it (mostly) hinges on the heart rate accuracy of wearables. Of course, not all of the devices I’ve been testing are wearables, which really muddies the waters. But we’ll get to that in just a bit.
First, let’s talk about sleep stages, how they’re defined, and how wearable trackers are supposed to discern one stage from another.
There are four stages of sleep, which can be divided into two categories: REM (rapid eye movement) and NREM (non-rapid eye movement).
- Stage 1 (NREM) happens immediately after falling asleep and lasts for about 10-15 minutes. During this stage, your brain activity slows, and breathing, heart rate, and eye movement all drop as your body prepares for Stage 2.
- Stage 2 (NREM) is more commonly known as Light Sleep. During this stage, your body temperature drops, your eye movement stops, and your breathing and heart rate normalize. This is also thought to be when your body catalogs memories. Stage 2 generally lasts for about 20 minutes but makes up most of your sleep as you flow between stages.
- Stage 3 (NREM) is Deep Sleep, and the heaviest sleep stage. Your breathing, heart rate, and blood pressure all drop to their lowest points, and your muscles are fully relaxed. Stage 3 is when your body enters its restorative phase for muscles and tendons; it’s also when bone repair and growth happens in children. People in deep sleep are hard to wake and will often be groggy for several minutes if woken from this stage.
- Stage 4 (REM) is Rapid Eye Movement. This is when the brain is most active during the night and when the most vivid and/or memorable dreams occur. As a result, the mind is active, but the body is essentially “paralyzed”—the body effectively shuts down arm and leg muscles, so you don’t act out your dreams in the physical world. It’s a failsafe. Your breathing and heart rate become irregular and hit their peaks during REM sleep. This is the stage when the brain’s restorative functions take place.
You’ll flow through the stages throughout the night, with Stage 2 commonly taking place immediately after Stage 4. Rinse and repeat. Of course, not every night is the same, and various factors can break this cycle. But that’s where sleep trackers can shine some light on what’s happening as you snooze.
As noted, each sleep stage is mostly defined by three variables: brain activity, heart rate, and breathing rate. While most wearables can’t record brain activity, they can hit the other two pretty easily. And that’s where products like Garmin, Fitbit, Whoop, and many others come in.
The thing is, wrist-based heart rate tracking is generally less than ideal, and you’ll often get very different results from different watches (or Whoop). And that’s really the first hurdle when it comes to sleep tracking. But as with most things when it comes to wearables, consistency really matters more than accuracy.
Garmin and Whoop seldom agree on anything when it comes to my sleep. Sleep stage data is always different. Respiratory rates, average heart rate, and time awake are also different. So, which one is more accurate?
I’m really not sure it matters. Getting in the ballpark is generally good enough—I know that I slept like crap, I just need my wearable to give me a bit of insight as to why. What sleep stage was lacking? While Garmin and Whoop never have the same numbers for each stage, they’re generally close enough that I can see where I’m lacking.
For example, if I sleep poorly and wake up feeling physically fatigued, there’s a good chance both trackers will show that I didn’t get enough deep sleep. Maybe Garmin spits out 22 minutes of deep sleep, while Whoop says I got 37. The odds are, both of these numbers will be low relative to the other sleep stages (especially REM). That tells me what I need to know.
Or, on the other hand, Garmin says I got 12 minutes of REM and Whoop says 32, and I’m having a hard time focusing at work that day, I’ll know the culprit.
At that point, it’s up to me to reflect on the previous day to figure out why my sleep may have been poor. Did I eat late? Was I especially stressed? Did I consume alcohol? Did I stay up too late? These are all things that can help me pinpoint a potential issue. And on a longer timeline, I can start to note the consistencies.
Of course, that’s just for wearables. When you get into devices like the Nest Hub, which isn’t a wearable at all, things get even murkier (read: less useful).
Okay, so we’ve established how sleep tracking works with wearables. But what about bedside trackers, like many apps or Google 2nd generation Nest Hub?
The Nest Hub (2nd Gen) uses a radar chip to detect movement, thus monitoring your sleep and restlessness (it doesn’t have a camera). You don’t get clear heart rate or sleep phase data from Nest Hub, but rather a focus on movement, snoring, coughing, and light changes. Interestingly, it still detects your respiratory rate with pretty decent accuracy. Because of this, it should theoretically be able to detect REM sleep at the very least, though it’s unlikely Google will add such a feature at any point. Getting data for only one sleep stage would be almost useless.
Still, this is a very different take on sleep tracking—or Sleep Sensing as Google calls it. Google’s goal with the Nest Hub is to help users learn more about how restless they are and offer tips on fixing these issues. For example, if you snore, the Nest Hub (or Google Fit, where the data is shared) might suggest elevating your head while you sleep.
Of course, this is the most simplistic form of sleep tracking, which means it’s the least accurate and most problematic. As noted earlier, the Nest Hub uses a radar chip to detect movement. That means if you share the bed with someone else, there’s a good chance it’ll get them in the mix, too. It does a decent job of detecting one person when you’re both in bed, but if you get up before your bedmate, all bets are off.
These days, I’m a fairly earlier riser—I’m usually out of bed around 6:00 AM every day, so I can work out before I start my workday. My wife, however, sleeps till 8:00 or so. When I get out of bed, she generally rolls into my spot and sleeps on my pillow. You know what the Nest Hub detects? Someone sleeping. For all it knows, it’s me.
Therefore, my sleep data from the Nest Hub is generally skewed in a bad way every day. If I go to bed around 10:00 PM and get up at 6:00 AM, but my wife comes to bed at 11:30 PM and gets up at 8:00 AM, all the Nest Hub “sees” is that someone was in bed from 10:00 PM to 8:00 AM and gives me the sleep data for those hours. It’s never comparable to the other sleep trackers I’ve been using (which are rarely comparable with each other but are still more similar than what Nest Hub provides).
Does that mean it’s useless? For me, yeah. But for someone who A) sleeps alone and 2) wants a birds-eye view of their restlessness and respiratory rates, maybe not so much. Google does a decent job of offering tips for getting better sleep if Nest Hub detects poor sleep hygiene—like setting a regular schedule, for example—which might make this a decent choice for some people. Personally, I find little to no value in how it tracks or the advice it offers, as most of the time, this is info I’m already privy to.
It’s also worth pointing out that Sleep Sensing on the Nest Hub is considered a “preview” and is “free until next year.” It’s unclear if Google plans to monetize this feature, though that’s how the verbiage reads. In case it’s not clear, this is not a service I would pay for.
Here’s the most important thing I’ve learned about sleep tracking: It only works with consistency and longevity. You’re not going to change your life in a night, a week, or even a month. True changes come in small increments over a long period of time.
If you want to know why you sleep poorly, you track your sleep and make note of changes. On a longer timeline, you’ll learn a shocking amount about your sleep hygiene that should help you figure out how to get better sleep.
Of course, sleep trackers can’t tell you everything. They won’t tell you if your pillow is causing issues. Or your mattress. Or if your spouse tosses and turns, preventing you from getting fully into deep sleep or REM. Or if the room is too hot. Or too cold. It’s up to you to experiment with these things to figure out what’s best.
You should start by tracking your sleep for several weeks on a normal basis—I’d say a month at least. Don’t make any changes for the first month so you’ll have an idea of how you normally sleep. Then start making changes to address what you might be lacking. Try a new pillow. Sleep with white noise. Wear an eye mask. Elevate your head (of feet!). Eat dinner earlier. Don’t snack before bed. Don’t wait until you’re totally exhausted to get in bed. Shower before you sleep.
There is a multitude of things you can try. But here’s the key: this takes time. Finding what works for you is trial and error, and with most forms of trial and error, you have to do things one at a time. You’ll also want to test things for multiple nights—a sample size of one isn’t really that helpful.
Sleep is the key that unlocks mental and physical performance for me (well, and nutrition). I want to know more than “I slept like crap.” And maybe you do, too. If so, then you should look into some form of detailed sleep tracking through a wearable, whether that’s from Garmin, Fitbit, or even Apple Watch.
The info that a wearable can provide, paired with a bit of trial and error, should help you better understand how you sleep and the things that affect your sleep patterns. If you’re willing to put in the work, it can be valuable.