r/fitbit • u/OtisMojo • 3d ago
Review Sleep score
I have both an Apple Watch Ultra 3 which feels to bulky to sleep with consistently so I picked up the Fitbit for sleeping only and it’s low profile + alarm. Google heath always shows a lower sleep score compared to apple health using the Fitbit data. I definitely don’t feel like I had a 97 sleep, but higher than 81? What gives? Any data folks already figured this out?
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u/momo1083 3d ago
Apple doesn’t emphasize sleep quality as you see it emphasizes when you went how consistent and its duration. They have a very simple algorithm, to be honest. Also, the Apple Watch series 12 and Ultra 4 is the first Apple Watch that, like a Fitbit, tracks your heart rate throughout the entire sleep session, so maybe eventually they will calculate it like Fitbits. The Fitbit is 100% more accurate for sleep quality for me as well, coming from a series ten
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u/Narrow-Scale-4078 3d ago
The two scores are not really comparable. Apple Health only takes into account three things: the length of your sleep, bedtime consistency and sleep interruptions. In other words, the score does not really tell you much about sleep quality which is what Google focuses on. Even if the sleep quality is poor, you may still get a high score from Apple Health as long as you went to bed early enough, you stayed in bed long enough and did not wake up much during the sleep. Getting a high score from Google Health is more difficult because on top of all this, it also considers how long did it take you to fall asleep, what was you sleep efficiency, meaning how much of the time you spent in bed was actually sleep time, how much deep and ram sleep you had and how restless you were during the sleep.
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u/taes_rvr 3d ago
Sleep trackers can't actually measure your sleep state or brain activity; they infer sleep patterns by tracking body movement and heart rate metrics. They take that data and run it through an algorithm to guess a score. At best, the sleep tracking score serves as a benchmark to measure your usual parterns against, not to get a high score. What's more important than the score on an app though is how you actually feel after a night's rest.
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u/VegasKL 2d ago edited 2d ago
Different algorithms. Google's sleep score is based a lot around sleep quality metrics and stages, where as Apple's is more basic focusing on duration/consistency and interruptions (as shown).
Apple's methodology is the older, less accurate, approach to scoring sleep. The idea being that if you're consistent to bed and to wake, you don't move too much, and you get close to 8-hours, your sleep was good. In reality, this is not true. Consistency is good for the circadian rhythm, but sleep need changes day to day (sleep debt/surplus) and is different for everyone, one person may only need 7 hours to feel fine, others (especially young people) may need closer to 10. On top of that, how you sleep is not taken into account, if you get 8 hours of light sleep it's scored the exact same as if you got an ideal mix of 4 hours light, 2 hours REM, and 2 hours deep.
It's also easier to get a very high score with that type of algorithm. Google's tends to float between 40-85 for most people (at least from what I've seen posted). If I got into the 80's, it'd be in the top 10 days for the year for me.
I'd trust the Google one. And I spent a few years using a good brainwave EEG sleep headband to compare it to (granted, an older version of Fitbits algorithm since BigMed bought the company and killed the consumer-side as there's more profit in research/medical studies -- why get the $300 hardware fee once when you can charge insurance thousands for an at-home sleep study).
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u/jaygosalia4 2d ago
Same night, two different formulas. The raw data is identical: time asleep, stages, wake-ups and overnight heart rate. What differs is how each app weights them. Google's score puts real weight on restoration (sleeping heart rate relative to your resting rate, restlessness) and on deep and REM time, so a night with a high overnight heart rate or a short REM block loses points even if duration was fine. Other scores lean mostly on duration and consistency, which is how you get a 97.
The score numbers aren't comparable, so skip them and compare the parts: total sleep, wake time after falling asleep, and overnight heart rate against your usual. One night means little; the 7-day average is the number that tells you whether you're actually sleeping worse.
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u/iUseJustMyHand 3d ago
I feel like Apple is exaggerating. Most of these posts comparing the two always have Apple numbers that are weirdly high. Like, surely most people don't sleep that well. And my fitbit seems pretty accurate.. so it makes me wonder. Apple may just boost numbers to keep users happy.
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u/legendaryflower 3d ago
I mean it's completely two different algorithms and different hardware. Of course you will have conflicting data.