Deep sleep accuracy?

The entire sleep tracking is sadly very disappointing.  It tends to record me as falling asleep before I even go to bed, or in REM sleep after I wake up in the morning. It misses times I wake up in the middle of the night, even when those times include me getting out of bed, even though it does record the steps I took during that time.

As for deep sleeping in the "11h and 34m" it supposedly record of me sleeping last night only 9m were deep, and only 13m were awake. I woke up several times last night, each time for longer than 13 minutes. Granted I also physically went to bed over three hours after it had me already a sleep (it claimed in I was asleep at 12:13am, but I didn't go to bed until after 3am and there were steps recorded in those hours.)  Though while last night with the supposedly over 11 hours of sleep had 9m record, the previous night with supposedly almost 8 hours of sleep had 50m, other nights over an hour and a half and some nights listed as -- (none).  

So for me it is kind of a nice idea, but really isn't all I hoped for, not that Fitbit is really any better.  My favorite wrist device was the Basis B1 which was discontinued years ago and replace with another model that was recalled after Intel bought the company and shut it down.  It is sad that years ago a company could do this really well and now with no other company has come close since. 

I have a lot of problems with sleeping, so yes I think it helps to understand the reasons why I sleep bad and what I can do about it. It monitors the progress I'm making.

There is an interesting article from DC Rainmaker about new sleep metrics in the latest Fenix 6 beta firmware. According to him it is going to come to the 945 late(r) this year.
https://www.dcrainmaker.com/2020/06/garmin-shows-off-new-on-device-sleep-tracking-widgets.html

If you have problems sleeping, go talk to a doctor!

Don’t take sleepmonitor on your watch to serious (or better yet, not at all)

Experts say it is not realistic to measure different sleep faces with a watch. And if it could it means not very much. There isn’t much you can do about it (except skip alcohol)

The thing experts do find interesting is the amount of sleep and wether you are awake at night. That is something you can do something about.

unfortunately garmin watches are not very good at detecting start and end time of your sleep or detect that you lay awake in the middle of the night.

I usually  don’t drink alcohol and when I sometimes do I look back. It should show more deep sleep. But none of it.

Again, if you have sleepproblems, don’t look at you watch, look at a doctor.

I have researched the limited information online about how Garmin and others, like Oura, track and report on sleep.  I have also had two conversations with Garmin about the sleep tracking on my watch.  The whole wearable sleep tracking world is really entertainment rather than true sleep analysis. Sleep tracking and reporting on the world of wearables is somewhat inaccurate and highly variable person to person.  What I have come to conclude about my sleep is this:

I feel I sleep well, although I do move around and reposition quite a bit. I have no trouble breathing and do not snore.  At times during the night, almost nothing will wake me up.  At other times I remember that I was sleeping lightly.  And at still other times I recall dreaming vividly.  My watch consistently reports zero to 10 minutes of deep sleep per night. I have no way to be 100% sure, but I believe that is likely inaccurate.  Someone further down in these comments reports over 4 hours of deep sleep.  That is also likely inaccurate.  Garmin analyzes heart rate and movement to determine sleep stages.  I move myself and my wrist quite a bit during sleep so the watch cannot really detect when I am in deep sleep.  Some people may move less so Garmin thinks they are in deep sleep even when they are not.

I feel like the reported REM sleep is more accurate for some reason. My watch consistently reports about 2 to 3 hours of REM, spread across several periods throughout the night. On the occasion that I wake up from a dream and notice the time, the next morning Garmin does report that sleep time as having been REM.

The light sleep reporting for me is probably too high because of the difficulty the watch has determining when I am in deep sleep.

Also, because the watch depends so heavily on the accelerator to determine sleep time and sleep stages, it is often inaccurate knowing exactly when I fall asleep.  If I am reading in bed before going to sleep the watch often reports that time as sleeping.  So because I do fall asleep pretty quickly, I am in the habit of looking at the time when I turn out the light so that I can adjust the sleep start time in the morning. In the morning, if I wake and then lay still in bed for several minutes before getting up – the watch shows me awaking, but then thinks I have gone back to sleep for those few still minutes before I get out of bed.

Most mornings I look at what the watch has reported and adjust the sleep and wake times accordingly.  There is nothing I can do to adjust or more accurately know my actual deep and light sleep times.

Maybe Garmin will become better with all this with future updates to software?  But likely it will take not only new software, but new hardware before at home sleep analysis becomes accurate.  Hopefully some real effort will be put into improving this feature.  Garmin recently make a big deal about bringing an on device sleep widget to some watches. They are now using the company Firstbeat for sleep tracking and analysis. Firstbeat adds a bit more detail to the analysis of the date and also adds a "coaching" aspect.  But as the actual hardware/software detection component has not changed significantly, all this really does is being the inaccurate information on Connect to the watch. It then adds some analysis and recommendations based on that inaccurate data but does nothing to improve the accuracy of the detection process itself.

I've gone from a Fitbit Versa to a Garmin Vivoactive and they're very different on sleep. I don't miss the Fitbit sleep score (which seemed to be one more thing to worry about), but I think the sleep tracking was better. OTOH, the Versa said I got about an hour of deep sleep at night, but hardly any REM while the Vivoactive says I barely get deep sleep (last night was an hour, probably the longest so far) but dream slightly less than half the night. I suspect the truth is somewhere in between the two.

My 735XT tells me I get 1-3 hours deep sleep a night.  It does correlate to what feels like a good night.

"Accuracy" is pretty relative here. This is from the study: "The matrix shows that that the classifier predicts deep, light, and REM sleep stages at roughly the same 69% accuracy rate. Wake is slightly more accurate at 73%. The most common mis-classifications are classifying true deep sleep as light sleep and classifying true REM sleep as light sleep." 

I started looking into this because this morning I woke up while dreaming, yet no REM sleep on my profile the last few hours of my sleep.  

Yeah you are right it even if you believe Garmin's %s.  I am on my 2nd FR245, 1st replaced under warranty.  I have never had anywhere near Garmin's published % in sleep time, wake time, or sleep stages. Another long thread on this is here: 

Sleep Tracking Issues - Forerunner 245 Series - Running/Multisport - Garmin Forums