I don't trust mine at all. Often I get up to feed the dogs/let them out at 4am, and then go back to bed for 2-3 hours... and Garmin misses those hours. Very often I'll take a 1-2 hour nap in the afternoon, and Garmin never picks that up. So I don't really trust whatever is does say.

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Athlinks / Strava

Same basic idea with me. I try to stay well hydrated, and drink a bit before bed = a couple of bathroom trips in the night. Often my watch doesn't have me going to bed until after my first trip to the bathroom or sometimes has me waking up after one of these trips. I'd say it's about as accurate as optical HR (which ain't that accruate!).

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I can't evaluate how it's working for you, but mine works pretty well MOST of the time. Sometimes, if misses the start of my sleep (late) by an hour or so. Otherwise, it seems pretty good. I actually sleep better because it is tracking my sleep. I don't think about it during the night anymore.

I find the sleep data on its own is not very helpful, I wish it would give some high-level takeaway percentage ala the Pillow app for the Apple Watch.

But, I do think the "Body Battery" usage of the sleep data is pretty good.

I think it is pretty good. The idea of using motion to detect sleep is relatively mature, and most of the new wearables do it well. I wear a Fitbit to capture sleep, but I have compared to my Garmin in the past, and I think the Garmin does it a tiny bit better.

What I look for is total sleep time and then my awake time. What I find is that if I eat poorly or drink, my sleep will get more restless and more awake time. Also, I know that if I get 6 hours of wearable sleep time and less than 45 minutes of awake time, I will generally be rested. So, if I have multiple days that are low, I will alter my behavior to bring my net sleep time up to 6 hours.

Thank you for the info

What is your average REM?

Deep sleep?

Thank you for the info

What is your average REM?

Average deep sleep?

They vary, of course. But my recent averages are 6 hours total sleep, 1:52 REM, 0:18 Deep. REM is usually about 1/3 of total sleep for me. Deep is always less than an hour.

My 30 day averages from Fitbit:

• 13% Awake
• 17% REM
• 56% Light
• 14% Deep

I this is based against 7 to 8 total hours measured (the counter starts when it thinks I first fell asleep, and ends when I get out of bed). So, it will count awake time in the middle of the night, and if I am restless and wake up before my alarm, it will count that as awake time.

basically... all the trackers just guess. They are generally good at telling if you are asleep (or at least, if you aren't moving watching tv/etc) but for insight into what's happening when you are actually asleep... all the studies I've ever seen say no.

If you are really interested in sleep cycle / tracking... there are some new head units that seem promising (DREEM looks pretty good) but they are expensive.

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Yep, the studies and abstracts I have seen have generally argued that actigraphy is almost dead-on with polysomnography in measuring total sleep and awake time. They deviate when it comes to precision around specific types of sleep (deep, REM, light). But, it is not a total guess either, just not as precise & true. My take is that the sleep breakdowns are in the right direction from the actigraphy devices. Also, the other caveat to consider when googling all the studies is whether they are studying "normal" subjects or people with an already diagnosed condition. When they get into usefulness for one of actigraphy vs. polysomnography for measuring subjects with a specific condition (insomnia, apnea, drug affects, schizophrenia, etc.) the conclusions may be very different from usefulness of the device for someone else.

My garmin regularly says I’m asleep when I’m not. It’s garbage.

It may be interesting to see what a Garmin 945 would say about Blood O2 saturation for someone with sleep apnea.

Mines stuck on 96 to 99% all of the time I'm sleeping. If you stop breathing it may show it.