| The accuracy of estimating sleep stages using heart rate and movement metrics is an interesting, and tenuous, subject. WRT to Fitbit and Oura the TLDR is that Fitbit and Oura aren’t accurate for slow wave (Deep Sleep) or REM. However, Fitbit is better at REM detection [1][2] than Oura. While sleep staging can be useful for identifying case sleep disorders, we know that the brain self-optimizes the stages of sleep you go through. So, what’s far more important than worrying about your rem or deep is optimizing getting time in any stage of sleep. Each stage is critical in a different way. If you care about improving your performance the measures you should care about—backed by strong scientific consensus and a plurality of randomized evidence—are sleep debt and where you are in your circadian rhythm. Sleep scientists call this the two factor model This reality drove us to create a sleep improvement app, called Rise ([https://www.risescience.com](https://www.risescience.com/)). We started both our research and company initially for elite athletes. We tell them what to do to improve their sleep tonight based on science. It's currently being used by both professional and collegiate teams across the NFL, MLB, NBA, MLS, and NCAAF. We've been taking what we've learned from athletes and adapting for us regular folk. If you're interested in joining our beta, sign up here: [http://bit.ly/hacker-friends](http://bit.ly/hacker-friends) [1] [https://www.ncbi.nlm.nih.gov/pubmed/28323455](https://www.nc... [2] [https://www.ncbi.nlm.nih.gov/pubmed/29235907](https://www.nc... |