Fitness trackers, heart rate, and sleep

[nakedfrog]

Now that I've had a fitness tracker for a while (a couple months), I've observed a trend that puzzles me just a bit. My average resting heart rate is 53 BPM, but my average heart rate when sleeping is 61 BPM.
Do any of you have a similar situation? To my knowledge, your heart rate is generally meant to be lower when sleeping. I've alternated wrists, and tried positioning it higher and lower on my wrist, but the data seems fairly consistent. Not an item of concern, just curiosity.
It's a Garmin Vivosmart 4.
It does potentially tie into another peculiarity, I tend to be a hot sleeper (nice for partners during the winter, not so great in the summer).
I'm in good health overall, BMI of 21, good blood pressure, good cholesterol, not diabetic, etc, VO2 Max 42-45, SPO2 readings average 95% while sleeping, some nights it briefly dips into the high 80s.
I do plan to ask my doctor for her thoughts at my next physical in March (obviously my fitness tracker isn't a "real" piece of medical equipment)

 

[nakedfrog]

I did ask my doctor, she also thought it was odd, but mostly thought maybe it was just an accuracy issue of the fitness tracker.
Lately I've pondered whether it's associated with my night-owlish tendencies, and maybe that's also associated with my lower heart rate during the day. I'd like to see more scientific study of "chronotypes" and delayed sleep phase syndrome/disorder. If I had my druthers, I'd probably be going to bed between 2-4AM and waking around 10-11AM.

 

[skyking]

I had an old Fitbit and now a new inspire 2. I too have a resting that has been cruising around in the 55~56 range but have not seen that trend. Mine dips down to ~52 several times a night. On accuracy:
I got an inexpensive arm band to link up to the new treadmill, as the fitbit does not.
They are within a beat of each other when comparing the Ifit workout graph to the fitbit. If they are inaccurate they are both doing it the same amount in the same direction
My bet is they are a pretty good tool. If I had the spare cash to waste I'd do a 3 way shootout with a chest band.

 

[eelw]

Overnight the other day. Yeah it was a SW glitch 🤪

 

[nakedfrog]

I had an old Fitbit and now a new inspire 2. I too have a resting that has been cruising around in the 55~56 range but have not seen that trend. Mine dips down to ~52 several times a night. On accuracy:
I got an inexpensive arm band to link up to the new treadmill, as the fitbit does not.
They are within a beat of each other when comparing the Ifit workout graph to the fitbit. If they are inaccurate they are both doing it the same amount in the same direction
My bet is they are a pretty good tool. If I had the spare cash to waste I'd do a 3 way shootout with a chest band.

Yeah, I'm skeptical that it's just specifically inaccurate when sleeping, especially since I tried wearing it a few different ways with no real change in the results.
I wouldn't necessarily be opposed to trying it against an inexpensive arm band in the future, though.

 

[skyking]

I am betting some software hinkyness myself.

 

[skyking]

my fitbit premium account tracks stats, and my resting HR is 55~56. It measures deep sleep by lower than average HR.
My HR was below the resting number for 82% of last night, for example.