Inspire HR: HRV data missing

[tesb]

In the last few weeks my FitBit app has updated with a Health Metrics tile. Resting HR and Breathing Rate measurements are updated regularly, but HRV data has so far only shown 2 data points across the multiple weeks. 

Is HRV measurement restricted literally to the nighttime? All other sleep measurements adjust for whenever a person might sleep (e.g  a shift worker sleeping for 8 hours in the daytime), but not this one? How is nighttime defined? 

Or is there another reason for the missing data? 

[ManuFitbit]

Hi @tesb. Thanks for getting back to us, and for sharing your HRV inquiry.

Fitbit uses the common formula called RMSSD to determine HRV from your recent heart-rate data. In the graph, your latest HRV measurement is from the longest sleep period over the past 24 hours. Only sleep periods greater than 3 hours are considered.

Can you please let me know how many weeks are you calculating the data?

[tesb]

hello

That didn't answer the question. The question was specifically, is HRV only calculated for periods of sleep during the "night time"? I've been mainly sleeping in daytime hours and have only 2 measurements since the tile appeared on 14th March. I'd guess these were the rare occasions I got some sleep at night.

This seems a regressive step. Before i got a FitBit i had a cheap, generic tracker that only tracked sleep at night time. Is FitBit now no better than cheap, generic trackers? 

Moderator edit: format.

[ManuFitbit]

Hi @tesb. It’s nice to see you again.

Thanks for your answer and for the question regarding the HRV. 

To responded your question: No. HRV will not be measure during the night time only.  As mentioned earlier, keep in mind that your latest HRV measurement is from the longest sleep period over the past 24 hours. Only sleep periods greater than 3 hours are considered.

If you still aren't receiving HRV, I recommend that you try restarting the device. In addition, please follow the instructions in this article to improve the accuracy of heart rate information and check the information mentioned here about other factors that could affect your heart rate reading, this has been useful to other users who have experienced something similar.