Should You Track Sleep?

man sleeping with sleep tracker deviceTracking certain things makes sense, if you go for that sort of thing. Tracking step count is hard without a device. No one’s going to count every step they take in their head. You’d quickly go mad doing that. Same with pulse rate and heart rate variability—you could count the number of beats for 30 seconds and double it to get BPM, but that gets unwieldy after awhile and HRV requires a special device. But tracking sleep? On the surface, sleep tracking seems futile and pointless. If there’s anything you should know intuitively without having to measure, it should be whether or not you got a good night’s sleep. You wake up and see how you feel.

Are you groggy? Irritable? Did you just crack an egg into the coffee maker, brush your teeth with light roast beans, kiss your dog good morning and let your spouse out to pee? You probably didn’t sleep very well.

Are you rested? Full of vim and vigor? Can you perform basic bodily functions without requiring a mug of coffee first thing? You probably slept fine.

Many people are fine with that much information. I’m one of them, actually. If I slept well, I slept well. But the argument for sleep tracking is more nuanced than that. It’s not just about knowing how well you sleep from night to night (which you can usually tell just from how you feel).

It’s about tracking how your daily actions, behaviors, exercise patterns, light exposure, food timing, and alcohol intake correlate with the quality of your sleep using actual numbers.

It’s about identifying the amount of deep sleep, REM sleep, and non-REM sleep you’re getting every night—and then using that information to make necessary changes.

Yes, with accurate sleep tracking, a person can do lots of things:

You can run experiments.

If you think something you’re doing, eating, taking, or implementing might be affecting your sleep, you can test it out. Eat the food/have the meal at said time/take the supplement/do the workout/etc. and track how you sleep. Remove the stimulus and track sleep again. What happened?

You can reinforce better behavior.

Sometimes it’s not about the accuracy of the device or the specific features of the device. It’s the simple act of measuring your sleep, thinking about your sleep, focusing on your sleep that compels you to get serious. It’s forking over a few hundred bucks on a sleep tracking device that finally gets you committed to a consistent sleep schedule. It’s the sunk cost of both attention and money.

You can discover triggers you weren’t even looking for.

When I asked people on Twitter about their biggest takeaways from using sleep tracking devices, one of the most popular answers was discovering a behavior, food, or exercise pattern that was hurting their sleep. Some named alcohol after 6p.m. Some named eating too large a meal after dark. Others mentioned too much exercise, or too little. The point is that people were using these devices to learn something about their own bodies. About what made them tick. They were gaining actionable information.

If you don’t have a strong intuitive relationship with your sleep, you can learn to develop it.

Many people have lost touch with their bodies. Using accurate trackers (like sleep trackers) can provide solid data that you can use to “sync up” with your subconscious intuition. Biofeedback can really help you become more intuitive, a better “body listener.”

At least, that’s how it’s supposed to work. That’s assuming the device you’re using is accurate. Are they?

A 2017 paper compared the accuracy of an OURA Ring to traditional polysomnography (the gold standard for tracking sleep cycles, waking, and sleep time) in a group of teens and adults.

  • The OURA ring was pretty good at tracking total sleep time (87.8% accuracy) and waking after sleep onset time (85.4% accuracy).
  • It faltered when tracking light sleep (65% accuracy), deep sleep (51% accuracy), and REM sleep (61% accuracy).

Overall, it’s good as a total sleep time tracker, but not as impressive as a sleep cycle tracker.

In teens, researchers compared the accuracy of a FitBit Alta HR and a Philips Respironics ActiWatch2 (two wrist wearables) to traditional polysomnography. Both consumer devices were accurate in tracking sleep duration but not sleep staging, which, “would benefit from further refinement before these methods can be reliably used for adolescents.”

In adults, the FitBit Charge 2 was compared to polysomnography. The FitBit:

  • Showed 96% accuracy to detect sleep, 61% accuracy to detect wake, 81% accuracy in detecting light sleep, 49% accuracy in detecting deep sleep, and 74% accuracy in detecting REM sleep.
  • Overestimated total sleep time by 9 minutes and light sleep by 34 minutes, and underestimated deep sleep sleep by 24 minutes.
  • Accurately estimated REM sleep duration.

Another study had similar findings, concluding that commercial sleep trackers are good enough for tracking sleep time and time in bed.

Some of these devices track more than just sleep duration and cycles (however accurately). For instance, the OURA ring also has a body temperature sensor, a heart rate variability monitor, and a heart rate tracker because all three biomarkers—body temp, HRV, and HR—can give insight into how a person is sleeping.  Are they accurate?

According to a recent study in women, the OURA Ring could detect menstrual shifts with 72–86% accuracy and ovulation periods with 83% accuracy by using nocturnal body temperature readings.

A newish wrist wearable called WHOOP was recently tested against polysomnography and actually did quite well:

  • It tracked deep sleep with 85% accuracy and REM sleep with 74% accuracy.
  • It got breathing rate within 1 breath per minute and pulse rate within 1 BPM of reality.

Plus, the adults using WHOOP reported improved sleep quality.

There are definitely problems with most of the current devices. They’re not as accurate as medical trackers. They rarely muster up to polysomnography. But they’re good for tracking overall sleep duration, and they’re getting better at tracking sleep stages. I imagine at some point in the near future we’ll have consumer devices that rival the medical ones.

And some of the newer ones, like the OURA Ring and WHOOP, can also track respiration rate and heart rate variability, which give insight into not just how you’re sleeping but also general preparedness and stress tolerance. I’ve explained the merits of HRV in the past, and although I’m not a devoted HRV-tracker, I recognize its usefulness. If I were an athlete again, I’d get a lot of use out of tracking my heart rate variability and having a “readiness” number waiting for me upon waking.

But overall, I’m not sold on their necessity

Imagine this: You get the newest, bestest tracker to finally figure out what makes a good night’s sleep. Except things get weird.

On the days you feel exhausted, your tracker reports the previous night’s sleep as having been exemplary.

On the days you feel rested, your tracker reports poor sleep.

Who are you going to believe? The tracker or your own experience?

This mismatch can throw off your ability to derive value and insight from the device. On the day you feel exhausted but should be rested according to the tracker, you ate a large meal at night with a glass of wine. On the day you feel rested but should be exhausted according to the tracker, you ate a small supper and had sparkling water instead of wine. Which nighttime routine will you pursue? Will you trust the numbers of your own intuition?

How you respond to this disagreement—who or what you believe—will have major ramifications for the rest of your day.

If you feel rested but the tracker says you slept terribly, you just might be inclined to believe the tracker. Do that often enough and you could become conditioned to feel dissatisfied with “good sleep.” You could nocebo yourself out of appreciating a good night’s sleep, or worse.

In one sleep study, what the researchers told participants about the quality of the sleep they’d had the night before had a greater influence on cognitive performance than how they actually slept. If they slept well but were told they slept poorly, they performed poorly. If they slept poorly but were told they slept well, they performed better.

Or—and I’ve seen this happen—you could become wedded to the numbers. That if you’re not able to track and validate a good night’s sleep and post the results to your Instagram account, it didn’t happen. I’ve heard from people who end up waking up in the middle of the night, stressing out over the quality of their sleep. Will the dog waking me up to go pee show up in next morning’s report and ruin my record for the week?

I have my leanings. As I said earlier, if I were a competitive athlete again, I’d probably be more inclined to give a sleep tracker a shot, especially if it had great accuracy and HRV capability. But this isn’t about me. It’s about what’s right for you.

Are you an intuitive who likes to feel things out and go with the flow, listen to your body?

Are you a number-cruncher who likes quantifying as much of the human experience as possible?

Most of us are a mix of both. It all depends on you—what makes you tick, what gets you going, what your goals are.

So, tell me, folks: Do you use a sleep tracker?

What do you get out of it?

What don’t you like?

Can you recommend any specific devices or apps?

Sell me on it. Or do the opposite. Make your case!

Thanks for reading, everyone. Take care and be well.


De zambotti M, Rosas L, Colrain IM, Baker FC. The Sleep of the Ring: Comparison of the ?URA Sleep Tracker Against Polysomnography. Behav Sleep Med. 2017;1-15.

Lee XK, Chee NIYN, Ong JL, et al. Validation of a Consumer Sleep Wearable Device With Actigraphy and Polysomnography in Adolescents Across Sleep Opportunity Manipulations. J Clin Sleep Med. 2019;15(9):1337-1346.

De zambotti M, Goldstone A, Claudatos S, Colrain IM, Baker FC. A validation study of Fitbit Charge 2™ compared with polysomnography in adults. Chronobiol Int. 2018;35(4):465-476.

Lee JM, Byun W, Keill A, Dinkel D, Seo Y. Comparison of Wearable Trackers’ Ability to Estimate Sleep. Int J Environ Res Public Health. 2018;15(6).

Maijala A, Kinnunen H, Koskimäki H, Jämsä T, Kangas M. Nocturnal finger skin temperature in menstrual cycle tracking: ambulatory pilot study using a wearable Oura ring. BMC Womens Health. 2019;19(1):150.

Berryhill S, Morton CJ, Dean A, et al. Effect of Wearables on Sleep in Healthy Individuals: A Randomized Cross-Over Trial and Validation Study. J Clin Sleep Med. 2020.

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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16 thoughts on “Should You Track Sleep?”

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  1. Got a Whoop in December. Something about seeing its number for predicted sleep need is convincing to me in a way that feeling tired never has been. I’ve been averaging over an extra hour of sleep since then, and realized I was chronically underslept for years.

    Hope I get to the point where I don’t need to rely on a gizmo to get me to sleep enough, but for now, it’s hugely beneficial.

  2. I use an OURA ring. I often don’t look at it until evening, so I’ve gotten through a lot of my day before I look at how it thinks I slept.

    Last spring and summer I kept getting “you didn’t sleep well” readings despite spending plenty of time in bed and not remembering waking up much. This got markedly worse after a firmware update and I thought the ring was malfunctioning. I was getting pretty tired, to the point that I needed naps, so I went to the GP. It turned out I had folate deficiency anaemia so bad that it was causing irregular heartbeat. I supplemented folate for a while (at the instruction of my GP) and started getting serious about greens and liver, and the numbers and my energy levels improved some after a few weeks. The GP also suggested sleep apnoea, but though I do snore, I didn’t think it was likely, because I was sleeping through the night (or so I thought), with the exception of getting up to pee. Anyway, I got a very bad cold and I started sleeping with a wedge cushion because I was so congested, and the numbers got way better within a week. I also stopped needign to get up to pee in the night (so, maybe the sleep apnoea wasn’t helping with the folate deficiency — maybe I was peeing it all out).

    It’s not perfect, but I probably wouldn’t have realised the wedge cushion made so much difference without it. I genuinely thought I was sleeping enough, and I was so convinced this was the case that I thought the ring was broken.

  3. Nope, I don’t track my sleep. My body tells me when I haven’t gotten enough. That’s sufficient information for me.

    The cutoff point. at least for me, seems to be 5-1/2 to 6 hours. It definitely isn’t optimal but I usually do okay, although I fade around mid-evening. Anything less than that is flat not enough to function on. On those no-sleep days we go out for dinner because I’m too much of a hazard to be in the kitchen.

  4. ..ah yes sleep… the thing I used to get plenty of, until menopause kicked it to the curb! … sigh… 🙁

  5. Well, it’s generally when I don’t kiss the dogs good morning (out of spite) because my wife and I are both clenching onto four inches of mattress at each side of the bed with two animals liberally spread out in between that I know I haven’t slept very well

  6. This article was timely for me as sleep had turned into another workout. Almost first thing I was checking my Oura app and often it was messing with my head because it was obviously wrong (couldn’t distinguish between pre-bed reading time and genuine latency) or telling me something that felt wrong – usually that I didn’t get deep sleep when I felt restored or that I had when I felt janky.

    This post led me to take the Oura off and just go to bed. I didn’t really sleep much differently, but all night and this morning I was just more relaxed.

    My time with the Oura was not a waste. I was able to see the correlations between late eating and alcohol keeping my heart rate up – which was a good reinforcement as to why they are not good ideas for quality sleep. I wish they had a mode where they went all Joe Friday and didn’t try to interpret or gamify the readings but just gave the facts.

    Just like tracking food and monitoring workouts, it’s useful until the tracking becomes the real activity and the activities are done just to get the tracking results. The practice is the prize, not some bogus score in an app.

  7. I’m rockin’ it kinda old-school. I bought a Pebble 2+HR a while back. No, those haven’t been made since 2016. Yes, it still works fine. The community has managed to create a new version of firmware for it and provide up-to-date apps to interface with it.

    The sleep stats are somewhat interesting. I suspected that I was running a sleep debt during the week and trying to make up for it on the weekends. That became pretty apparent, just looking at the relative numbers. If the numbers are anywhere near accurate, I was logging at least 9-10 hours of sleep debt during the week (assuming 8 hours / night is ideal) and not recovering anywhere near that during the weekend. I’ve adjusted my sleep patterns appropriately; no matter what I do, 7.5 hours / night seems to be about the best I can average, long-term. I’ve gotten comfortable with that figure. And I’m not needing excessive amounts of sleep on the weekend, anymore. Like I said, I suspected I was doing this and the metrics from the watch made it clear.

    The biggest benefit for me is the smart alarm. I set an alarm with a 30-minute timeframe. The first time I drop into light sleep, within that timeframe, the alarm goes off. I’m not waking up groggy, so often. All too often, in the past, the alarm went off at the set time and, if I happened to be in a deep sleep cycle, it would take HOURS for me to work off the grogginess. That’s not been so much of a problem, lately.

    I’ve encouraged multiple other smartwatch owners to find an app which does this and they’ve reported being more refreshed in the morning, as well. One of them mentioned that she knew that, if she slept too long, she was groggy all morning. Apparently, that “slept too long” was getting into another deep sleep cycle. Since going with a similar app on her Samsung, she’s reporting less grogginess, as well, because her watch is waking her up when she’s in a light sleep cycle.

  8. I think monitoring my sleep would just stress me out more. I know I don’t sleep when I see every hour tick by. I probably average 10 hours in bed and on a great night I may get 5-6 hours of sleep. The last couple of nights it’s been more like 2-4 hours.

  9. I’ve been using a sleep tracking app on my phone for around 6 years. Sometimes I think I feel tired because it says so! Not good. It has shown that over that time, it’s taking me longer and longer to actually get to sleep, I’m 49, maybe menopause is ramping up. Apparently, I sleep 4% worse when it’s foggy!! Go figure. I’ve not managed to work out why I don’t sleep well but suspect it’s a blue light thing and I can’t see to help myself.

  10. I think it’s too much to worry about. As long as I feel good in the morning (as this article points out) I trust that I slept well. I don’t like tracking my calories for long periods of time either. I think it’s unnecessary for my personal situation but I do it occasionally to get a good overview of what I’m doing – macros and micros as well as overall calories. It would be interesting to see my sleep results but not worth the investment these devices require.

  11. I wonder whether these devices actually disrupt sleep. They certainly disrupt bioenergy fields. As a biodynamic craniosacral therapist I ask clients to remove their devices before a session because they blank the field and I can no longer feel their systems. With, as opposed to without, is clearly discernible.

  12. I often wear my Garmin running watch while sleeping. I have found it useful. I’ve mostly gotten to where I already know alcohol after 5 is a no go, and my cycle affects my sleep. I do still track symptoms and sleep because I’m in peri menopause and I’m not at all regular.

    The watch knew, by the way, that I got zero sleep on that overnight flight to Europe last year. I don’t need the watch but it helps me recognize that 8.5 hours or more is best.

  13. Yeah, I started leaving my Garmin watch on at night as I wanted to test different effects of behaviour. Alcohol, late snacks, late exercise etc. Sleep patterns is not what I get the most out of. I know that if I get 8 hours of sleep I’m usually fine. But Garmin has this body battery measure which is probably not exact, but I see a pattern here. Alcohol, late exercise (cardio) and late snacks affects my ability to ‘recharge’ fully. And this is without exception – when I wake up after days with late snacks/alcohol or late cardio exercise (7pm an on) I do not fully recharge.

  14. I used the Sleep Cycle app on my phone for about 6 years and it was fascinating to see my circadian rhythms. My learning from this was that I was convinced I went to bed at certain times but in reality, my routine drove me to having less sleep than I thought. The correlation with alcohol is stark and direct.
    I’ve recently switched to wearing a Garmin Venu and with the stress monitor and body battery this is really insightful again. It makes me think twice about some of my choices and be conscious about my sleep more than I ever was.

  15. I have a FB Charge 2. To me it seems very accurate. I’ve had it for years. It’s a very reliable little device with great battery life.

  16. We’re so out of touch with ourselves that we need a device to tell us how well we’ve slept… come to think of it, that’s actually sad. But if it helps to reconnect with our body…? why not. I think we should use all the help we can get to improve our lives.