Fitbit’s New Sleep Tracking: Testing The Alta HR

screenshot of the sleep stage graph on the fitbit smartphone App

2019 update

I originally wrote this article back in 2017. Rather than changing it all, I wanted to keep the original content for those interested in my earlier impressions, and to be able to see how Fitbit has changed if you’re interested.

However, there are some important points worth noting as you read the article:

  • I refer to the Sense and Jawbone trackers, but they were both discontinued. However, Jawbone Health is being worked on and will hopefully mark a return to wearable trackers.
  • I no longer use the Alta HR myself, preferring the Versa. You can also see how that performs in my multiple sleep tracker test.
  • I now prefer devices with a color screen rather than the thinner bands I used to.
  • In 2019, Fitbit introduced a paywall for some sleep tracking data, which has not gone down well with some users (see the Fitbit community forums for some heated debates!). I don’t know if it will last, but at the time of writing you need to pay a monthly subscription for Fitbit premium to get personalised sleep insights and some more complex data. However, the sleep data I wrote about in the original article is still available for free.

The original article

my fitbit alta

In 2017, Fitbit made some major changes to its sleep tracking. The Charge 2 HR, Blaze, Alta HR and Ionic now provide sleep stage tracking, better sleep insights and other helpful extras like sleep schedule reminders.

Like all home sleep trackers, however, Fitbit devices have historically struggled with accuracy problems, both with activity and sleep tracking.

But while some, like the Jawbone and Sense for example, appear to have fallen by the wayside under the strain of constant criticism, Fitbit appear keener than ever to improve both the accuracy and helpfulness of their devices and App.

So to find out more about the new sleep tracking, I decided to wear an Alta HR for a month to see just how accurate and useful the sleep data on the App, reminders and insights proved to be.

What I was looking for

I regularly test new activity and sleep trackers, but I also like to have one for real personal use, rather than just being a part of my ongoing tests.

And for me personally, there are a few things that make it more likely I’ll stick with one, rather than leave it in a drawer after I’ve finished reviewing it:

  • It looks good – this matters if you wear it constantly and have to take it to bed with you!
  • It feels comfortable to wear during the day and in bed.
  • It appears accurate on measurements I can test myself, such as heart rate and steps. And to a certain extent, the time I probably fell asleep, times I woke up during the night and in the morning.
  • The App is easy to use, understand and interpret.
  • The App provides useful, actionable tips to help me sleep better.
  • If there are useful reminders to take action, such as do some exercise or get ready for bed.

Some of these points apply to the specific device, of course. And others apply to all of the new Fitbit devices, such as the sleep data on the App.

Since this is intended to be a look at the new sleep tracking, rather than a detailed review of the Alta HR itself, I’ll cover it only briefly before looking at the Fitbit sleep tracking that’s the same for other devices.

Why I chose the Alta HR for the month

Having worn many different trackers on my wrist at night, I know that I prefer them to be as comfortable and unobtrusive as possible.

The Alta HR ticks all of those boxes. With a similar look to the Charge 2, it’s considerably thinner. And it’s not far off the previous champion of lightweight wearables – the Jawbone UP3.

And like the Charge 2, it also looks great on the wrist. Many devices look a bit ugly, are too bulky or worse still, both. And that doesn’t inspire long-term use. But I thought I’d be happy keeping the slim and sleek Alta HR on for a month, and I was right.

Another key point is that it has a fantastic battery life – one week with a single charge. And that means less risk of not using it because you can’t find the charging cable or you forget to put it back on again!

photo of the alta HR and jawbone uP 3 both on my wrist
The Alta HR compared to the lightweight Jawbone Up 3

First tests – basic accuracy

The sleep stage breakdown is largely possible because of the ability to combine data from both the movement and constant heart rate sensors. So to trust the sleep data, it would be helpful if the movement and heart rate appear accurate during the daytime too.

Where heart rate is concerned, the resting heart rate appears very accurate. I tested it against my pulse and stopwatch many times during the month, and it was pretty much always spot on.

When it came to heavy exercise, however, it was a whole other story. The Alta really struggles to keep up when I’m at the gym – possibly because of the constant wrist bending when lifting weights and rowing, which Fitbit themselves admit can cause problems.

But during the night, that shouldn’t be an issue. So I’m reasonably satisfied that when I’m not moving, the heart rate reading can be trusted (as long as I don’t lie in an awkward position!).

As for less vigorous movement, again it seems pretty good. It counts my steps well during the day, and reacts automatically to exercise such as walking or cycling. And importantly, when I get up in the night to use the toilet or get a drink, it hasn’t missed it once (more on that later).

An important point here is that this is the kind of initial testing the average person might do with a new device. And if a device passes these tests, it’s more likely the owner will trust the more complex data like sleep stages.

Setting a sleep schedule and reminders to stick to it

One of the things I really liked during the month is the option to set a sleep goal / schedule and then get reminders to stick to it.

In the App settings, you can input your target sleep schedule. Since I’m a bit of a night owl, I went with bedtime at 12:30 a.m. and wake up at 8:30 a.m.

You can limit the days for your schedule if you like, but I know I personally benefit from a regular 7 day a week pattern.

Following that, you can ask for a reminder to help you wind down for sleep, which I set an hour before at 11:30 p.m.

Every night I then received both a notification on my phone and a vibrating reminder on my wrist to encourage me to stick to that bedtime. And in theory, start winding down by putting aside any late night work, and reading a book or relaxing rather than watching the next episode of my favorite TV series.

I found this a very helpful tool, and one which I can see actually benefiting people. And to help motivate you even more, if you manage to hit your target you’ll get a green star on the App the next morning.

So let’s take a look at the App data and how useful it might be.

App page 1 – the dashboard

fitbit app page 1 screenshot

The above screenshot shows the summary on the dashboard on the Fitbit phone App. It’s Monday morning and I’m working from home, so there’s not much activity logged as yet (wait till my gym session this afternoon!)

The important part, for now though, is the sleep section. It shows 8 hours 12 minutes total sleep time and 69 minutes awake during the night. I did have a bit of a restless night, so that makes sense.

To find out more about my sleep, you then click on the sleep section to get more detail.

App page 2 – a closer look at my total sleep

screenshot of my fitbit app sleep data for the last week

The second page of the App shows you two main things: a visual representation of how much total sleep you had in the last week on top.

And below there’s a scrollable list of all your previous night’s sleep – mine goes back over a year, even registering my Charge 2 and Blaze data.

What’s immediately clear is that I got a green star last night for hitting my personal total asleep goal of 7 hr 30 min. Great!

I can also see that it’s only the second time I’ve hit it in the past week, falling behind on the other 5 days. Not so great, so perhaps I need to think about why that is and pay more attention to my sleep schedule.

App page 2 continued…

screenshot showing the fitbit app previous week

When I scroll further down the main sleep page on the App, I can see some problems with the past week. For one, I’m regularly going to sleep later than my target time of 12:30 a.m.

Secondly, I’m really not doing very well at waking up at the same time and getting out of bed! My wake up time has a 2 hour range, and something I really need to improve.

The good news is that I did actually got to bed much earlier than the times recorded, but was just in bed reading. The fact that it hasn’t recorded that as sleep is very important, and a relief to see.

Capturing a bad night’s sleep

An interesting point in this last week though is what happened on Friday. I was ill that night and slept badly. I took the morning off, and tried to get some more sleep to recover. And the Fitbit was very accurate in recording those 2 separate phases of sleep.

It doesn’t record stages if the sleep is less than 3 hours, so the 1 hr 37 min sleep is just a total time. Nevertheless, I was impressed that it picked up the total time for both phases.

I do think the first phase is a bit inaccurate, however, as I felt like I slept less and was awake in bed resting. A classic sleep tracker problem which unfortunately still crops up from time to time. But it still highlights well the general idea that it was a bad night’s sleep.

Overall, I like the way you can see the total sleep time for each day, an average for each week and stars for when you hit your sleep goal. It looks good visually, is easy to read and understand. And the patterns make you think about how well you’re meeting your goal or not.

App page 3 – the sleep stages

fitbit app sleep stages

When you click on any of the days in the previous page, you’ll find the sleep stages for that night. This is where you start to see your sleep in more detail, and also potentially get a little confused. So it’s interesting to see how Fitbit decided to present the data.

First of all you can see your stages all together, presented in a pretty chart. Even though there are technically more stages, Fitbit chooses to group them into awake, REM, light and deep.

Unless you have a good understanding of the science behind sleep stages, the chart is kind of meaningless though. So it’s good to see the total for each stage broken down into times and percentages below.

But what does 49% of the time spent in Light sleep mean though? Is 1 hr 50 min of deep sleep the right amount or do I have a sleep disorder? These are the kind of questions I wanted to see answers to, as I imagine most people would.

And to get some answers, it seems you have to look in 3 different places.

Information about each stage

deep sleep stage screenshot

When you click on the main sleep stage graph, you can access 4 more pages – one for each of the stages. That way you can visually see when you were in that stage during the night, as well as the exact times (if you click the bars). And underneath are a couple of key notes about that stage.

In the above screenshot, I’m told I was in deep sleep for 19% of the night. I did wake up feeling refreshed, so going by the key notes, logically I can assume 19% might be a solid time.

But that’s assuming the total time was enough that 19% of that total time can be considered solid. More on that point later.

The notes are brief, but all useful. I like that you’re told it’s typical to wake 10-30 times per night. That’s a helpful bit of information that might stop you feeling anxious about your sleep data.

And it’s good you’re told REM sleep typically occurs later in the night. Again, that might stop you worrying when you realize it’s missing from the first part of the night.

Benchmark against your gender and age

fitbit app benchmark data screenshot

The screenshot above shows perhaps my favorite part of the new Fitbit sleep tracking data: the benchmark against people your age and gender, and also against your own 30 day average.

Assuming it’s accurate, to me this is a fantastic way to help people feel less anxious about their sleep. And of course, it’s actually telling you something useful about the sleep stages, rather than just leaving you to work out what all those graphs mean.

For last night’s sleep, the App tells me that my sleep is surprisingly average for men my age. I’m almost exactly in the middle for awake, REM and light. And I even got more than average deep sleep, which is the stage that leaves you feeling refreshed.

So going by these results, I might assume I have nothing to complain about. But before I start editing my status as an insomniac, there’s a small caveat.

These are benchmarks regarding percentage time in each stage. They don’t take into account whether you actually slept for long enough for those percentages to be enough in total.

At the end of the day, how you actually feel in the morning will still tell you more about whether you got enough sleep than graphs, percentages and benchmarks on an App.

That’s not to take away from the potential usefulness of the comparison though. If you regularly get much more or less of a sleep stage than the average person, it might be a good idea to mention it to your doctor to see if they think it needs to be looked into.

More information about sleep stages

I mentioned that there were 3 sources of answers about the meaning of your sleep stages. We’ve seen the individual breakdowns and key notes, and also the benchmarks.

The third is the Fitbit sleep tracking page on their website, which you’re taken to if you click ‘learn more’, which appears next to the sleep stages. There you’ll find further clarification of the sleep stages, though it still doesn’t clarify points like how much time in deep sleep could be considered ‘solid’.

I think that’s partly because we’re all different, and our sleep will vary from one night to the next naturally. So again, the importance of knowing how much sleep you need to be at your best can’t be understated.

Once you know how much total sleep you need to feel good, you can enter that as your sleep goal. Then hopefully the sleep stages will fall into the average range in the long-term, helping you feel good about your sleep pattern and motivated to stick to a good sleep schedule.

Sleep insights / coaching

Either my sleep is better than I thought, or I just haven’t worn the Alta HR for long enough yet, because I haven’t received any useful sleep insights so far. I know they will eventually come as the device gets to know me better, so hopefully by the next article I’ll have some to discuss.

What I did receive though is a couple of emails reminding me of all the different sleep features I can and should be making use of. I like that Fitbit follow you up this way, gently motivating you to do important things like set sleep goals and reminders.

Update note: for some reason, the insights never arrived when I had the Alta HR. But they do now with my Versa, even though they are general and would only be personalized if you go premium.

How accurate was the Alta HR overall?

Overall sleep and wakings

I kept a close eye on the things I could objectively record over the month. On most days, I was happy with the falling asleep time and waking time. However, there were 3 days when I felt it was off by more than 5-10 minutes and so changed the data manually.

On the day I was ill, I deleted 40 mins sleep when I was definitely awake in the night and not moving much. And on two other days I deleted 20 in the morning when I woke up and stayed in bed, unable to fall asleep again.

Impressively, there were no mistakes when I got up to use the bathroom or get a drink from the kitchen.

So I think there were 3 days in the month where the accuracy was off by enough for me to feel the need to adjust it manually. Personally, I’m quite happy with that as it’s not as bad as many other sleep trackers, and it’s accurate enough for me to feel like it’s useful.

Sleep stages

photo of my phone with the fitbit sleep app on the screen

The problem with judging the accuracy of the sleep stages is that, well, you can’t. Not unless you wear the device in a sleep center and compare it to a polysomnogram.

To a certain extent you can use the benchmark with your past 30 days and other people, combined with how you feel, to get a very rough idea of the accuracy. But really, you’re left to trust the claims of the manufacturer where accuracy is concerned.

Fitbit have never claimed to be 100% accurate, using words like ‘estimate’ carefully. But in April 2017, some interesting research was published in the journal sleep, in which wearables were in fact compared with proper sleep lab tests.

The researchers apparently demonstrated that wearable devices which track both movement and heart rate are more accurate than previously, concluding:

These results suggest that a wrist worn device with movement and cardiac sensors can be used to determine sleep stages with a reasonable degree of accuracy in normal adult sleepers, but without the cost and artificial sleep environment of a sleep laboratory. The reported performance figures are similar or better than previously reported results from non-EEG based sleep staging using combinations of cardiac, respiratory and movement information.

This research was supported by Fitbit (make your own judgment on that!). But it does suggest home sleep trackers might be entering a new era where reliability is concerned.


Personally, I like Fitbit’s new and improved sleep tracking. Even though it’s impossible to say just how accurate it really is yourself, it does seem more accurate than it used to be at least.

A year ago, my Blaze and Charge 2 sometimes added up to an extra hour to my sleep if I was awake and motionless. And although there were a few mistakes during the past month, there was nothing that wildly inaccurate.

I’ve found the sleep goal setting very useful, even if I’m struggling to meet it. But it’s constantly on my mind now, so I’ll be trying to get more of those green stars!

I like the idea of the sleep stage benchmarks. Again, I can’t be sure if it’s completely accurate, but I can be sure it makes me feel better about my sleep. I almost always fall under the ‘normal range’ for men my age, and even though I take it with a pinch of salt, it’s still kind of a relief to know.

As for the Alta HR, this wasn’t meant to be a review of the device itself. But I should end by saying it’s grown on me over the weeks. It’s like the smaller sibling of the Charge 2, and although I first missed the mindfulness App and the more accurate exercise tracking, I really like the thin design and great battery life.

You might also like

For more information about the accuracy and reliability of sleep trackers in general, you might like to read about the way sleep trackers work.

Your thoughts

If you use a Fitbit, how have you found the new sleep tracking so far? Which features do you find more or less useful? And does it seem accurate to you? Feel free to leave a comment below with your thoughts.

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