How accurate is the sleep measurement?

[Mardi50]

I'd like your thoughts on how accurate the sleep measurements are.  There are days that I feel like I slept terribly and have a sleep score in the 80s and times I feel like I slept great and have a sleep score in the 70s.  I'm very skeptical about data that fitness monitors collect, yet I still wear my Fitbit religiously.  Thanks!

[LZeeW]

@Mardi50   Fitbit's sleep tracking has a very good reputation.  Premium users get more detailed sleep analysis.  This detailed information can explain a lot, compared to non-Premium sleep stages and score.  There are three section in the breakdown, with a possible 100:

• Time Asleep:  This is 50% of the score - highest possible 50/50 points.  Your time asleep is your total time in bed, minus the time you're awake.
• Deep and REM sleep:  This is 25% of the score - possible 25/25.  This is what you see in your sleep stages graph, but this is only 25% of the score.  Sometimes I'll get a lower score than I expect, then I look at the graph and benchmark data and see that I had very little deep and REM sleep.  You get benchmark data that compares you to others in your age group.
• Restoration:  This is 25%of the score - possible 25/25.  It includes how restless you were and looks at your sleeping heart rate.  Your heart rate usually slows in your sleep.

I found out things about myself by using this sleep data and making changes.  I feel like I'm the textbook example of a human circadian rhythm.  I really need to be in bed by a certain time or I get a crappy score.  I can eat chocolate in the daytime, but evening chocolate is bad for sleep for me.  Alcohol makes you feel sleepy, but it really messes with your deep and REM sleep.  Sometimes my score is lower than I expect to see because my heart rate didn't go as low as usual, most commonly because of food or certain wines too close to bedtime.

I hope this gives you some insight.  I have Premium and my husband doesn't.  I keep trying to explain to him why he gets the scores that he gets.  Fitbit has a two week Guided Program called Habits for Restful Sleep.  Please take a look at it.  I personally don't recommend buying Premium just for this feature.

[Mardi50]

Wow! Thanks for such a detailed explanation! I’ll have to take a deep dive into the data that I’ve collected.

[LZeeW]

@Mardi50   Glad I could help.  I'm moving your post to the Sleep Well forum.  It will help others with the same question.