I’ve stumbled upon a very good write-up about the accuracy of Oura sleep tracking measurements and why it is a problem, with links to proper research including the one that Oura team themselves are using as reference: https://nutritionalrevolution.org/2019/07/20/why-the-oura-ring-sucks-for-tracking-sleep-and-might-be-harming-your-health/ (cached).
Apparently, they have done a well designed scientific study on how well Oura tracking was compared to other professional lab methods of sleep tracking.
“From EBE analysis, ŌURA ring had a 96% sensitivity to detect sleep, and agreement of 65%, 51%, and 61%, in detecting “light sleep” (N1), “deep sleep” (N2 + N3), and REM sleep, respectively. Specificity in detecting wake was 48%.”
Specificity in detecting wake was 48%! If this was a medical test, it would never be approved by FDA.
A specificity of 48% means that there is a 48% chance that someone is awake when the device says they are asleep.
That is horrible.
This is very surprising and alarming. As the author later goes on to describe, this has real implications and possible negative effects, this is not just a benign error here and there. Users are apparently supposed to use the Oura data to change or at least adjust and improve their sleep habits, and of course if they will do it based on faulty information, the adjustments themselves are going to be faulty and it can lead to worse or sub-optimal sleep!
Apparently you can still use Oura to track heart rate and HRV, but their own proprietary markers like “readiness” are probably based on all of their data including sleep, so they are not going be that accurate either.