The data shows a correlation between heart rate and sleep length. That's the length of actual sleep as opposed to the time spent in bed. This correlation could mean that 6.5 to 8 hours of sleep may be optimal for health. That's because resting heart rate is generally considered a signpost of wellness.

Of course, how those hours slept are broken down into REM and Deep Sleep is a factor. With 250 million nights of sleep analyzed powered by machine learning with Polysomnography-grade accuracy we are learning more every day and happy to share some of that knowledge with the community.