: Why is it recommended to have 8 hours of sleep when sleep cycles happen every 90 minutes, wouldn’t waking up at 8 hours be in the middle of your cycle?

Question

I’ve learnt a little about sleep cycles and remember that every 90 minutes is when we move through the 5 stages of sleep, but I’ve also heard it’s recommended to have 8 hours of sleep. Wouldn’t that make you feel drowsy if you’re interrupting the sleep cycle when you wake up after 8 hours?

In: Other

Answer 1

The eli5 is that *all* of these numbers are vague, rounded approximations. Human biology doesn’t happen to run exactly in sync with round units of time.