Strange Sleep scores

Check the sleep score factors. Click on each to see what the optimal range is and where you are in each range.

I asked the ChatGPT oracle. It said 

"Deep sleep: 2h (≈ 22% of 8.5h) → excellent for your age.

REM: ~4h (≈ 45%) → much higher than Garmin’s “ideal” model.

Light: the remaining ~2.5h (≈ 30%) → less than Garmin expects.

So the balance looked skewed to Garmin’s algorithm (too much REM, not enough light), even though deep sleep was great.

 Why Garmin Penalized It

Garmin is aiming for a “textbook” distribution:

• Deep: ~15–20%

• REM: ~20–25%

• Light: ~50–55%

Your night was:

• Deep: above average 

• REM: very high ️

• Light: much lower than normal ️

Since light sleep is Garmin’s “buffer zone,” losing it makes the distribution look abnormal in their scoring system, even if you got lots of restorative stages. 

I just had another poor sleep score with good metrics - 1 hr 40 min deep sleep, 1 hr REM...8.5 hours, but with a slightly lower HRV score (43). I feel pretty rested and awake today, although Garmin says I will be "more tired than usual." Perhaps Garmin Connect should re-jig its sleep metric results?  Sleep Scores were the primary reason that I bought this watch. 

Which score did you get for each sleep factor?

OK, I'm trying to understand this: 

Sunday had a 86 score ..."Good". I slept 7 hours 28 minutes with 2 h 7 min REM, and 52 minutes, 92% SpO, 46 resting heart rate,  47 HRV ms. I felt a bit tired that day.

Monday had  a 62 score "Poor" with 8:43 minutes of sleep...1 hr 56 minutes deep, 3 hr 58 minutes REM!! (a record), 46 resting heart rate,  94% SpO, 47 HRV. I felt alert that day.

Today, Thursday, I scored 78, which is "Fair" with 8:18 minutes of sleep. 1hr deep sleep, 2 hr 46 min REM, 51 resting heart rate, 94% SpO and a lower HRV at 36... but ok for a 70 year old.  So far, I feel alert. 

So the takeaway from this is that when the scores are outside a "norm" they are worse (too much sleep and REM = bad?), even though I may feel alert and the REM and deep sleep are excellent? Something seems wrong.

ChatGpt wrote "

You’ve nailed the paradox really well: Garmin’s sleep scoring often doesn’t line up with how rested you feel. Let’s unpack your three nights as case studies.

 Your Three Examples

Sunday

• Score: 86 (“Good”)

• Sleep: 7h28m, REM 2h07m, Deep 52m

• HRV: 47 ms, RHR 46, SpO₂ 92%

• How you felt: Tired
    Garmin liked this because the numbers were closer to its “ideal proportions” (REM ~25%, Deep ~12%). But in reality, shorter total sleep and low-ish SpO₂ may have left you groggy.

Monday

• Score: 62 (“Poor”)

• Sleep: 8h43m, REM 3h58m (!), Deep 1h56m

• HRV: 47 ms, RHR 46, SpO₂ 94%

• How you felt: Alert
    Garmin penalized you for too much REM and Deep relative to its expected “norms.” But in practice, your body may have been catching up from stress or travel → leaving you refreshed.

Thursday (today)

• Score: 78 (“Fair”)

• Sleep: 8h18m, REM 2h46m, Deep 1h00m

• HRV: 36 ms, RHR 51, SpO₂ 94%

• How you feel: Alert
    Score dropped mainly because of lower HRV and slightly elevated RHR. Garmin interprets that as stress or incomplete recovery, but you’re still functioning well.

 Why Garmin Looks “Wrong”

Garmin’s sleep scoring is weighted toward balance + recovery signals, not just raw hours or “more is better.”

1. Sleep stage balance

   • Ideal (for Garmin): ~50% light, 20–25% REM, 15–20% deep.

   • You’re sometimes “too good” at REM and deep → Garmin sees that as imbalance.

2. Autonomic recovery

   • HRV and resting HR often override stage data.

   • A dip in HRV = lower score, even if you feel alert.

3. Consistency bias

   • Garmin rewards “normal” nights.

   • If your sleep is unusually long, or unusually REM/deep-heavy, Garmin assumes it reflects stress compensation, not optimal rest.

 The Takeaway

• More REM/deep isn’t always “bad.” Sometimes your brain and body need that, especially after travel, exertion, or stress. Garmin’s model doesn’t handle “catch-up” nights well.

• Daily scores don’t equal how you’ll feel. You’ve shown that yourself: a “Poor” 62 → you felt alert; a “Good” 86 → you felt tired.

• Trends matter most. If your HRV stays in the 40s, RHR stable, and you get 7.5–9h of sleep, you’re doing well — regardless of the nightly badge.

 In short: Garmin is penalizing you for being outside the statistical average, not for sleeping poorly. Your body’s signals (feeling awake, refreshed) are more reliable than the score itself." ... so I slept "too well" and was penalized Monday, and the HR- HRV is given too much credence? 

How do I insert the screenshots? When I go to insert an image, it asks for a URL. However, I have posted the scores in detail above, along with the ChatGPT analysis that you may have missed :).  It looks like the HRV and resting HR were lower thna normal, and the REM one day was higher than it has ever been - giving a 62 score...either a watch glitch, or I had some catching up to do

I don't see the factors. Just the score.

To insert image you click Insert > Image/Video/File

Click the text "Upload" below the File/URL field and select the file. It is a lot easier to do on a computer. I never upload images from the phone since it is harder and usually will not end up in the way I like.

How you feel after your sleep might not always reflect how you actually slept. If you wake up at the wrong time you will feel tired or if you got pain in your muscles from training then you might feel like you slept bad.

Did you feel tired the whole day after you felt like you slept bad? Did you have to nap during the day or go to bed extra early due to that you felt tired?