My Apple Watch says I'm getting 90 minutes of deep sleep — is that enough?

Two sleep doctors explain what deep sleep is, how much we need and the real number you should be looking for on your Apple Watch sleep tracker.
CNET

A Ring and a Smart Bed Tracked My Sleep for 30 Nights. Here's What I Learned

How does a sleep tracker on your finger compare to one in a bed? I tested Sleep Number and Oura for a month to find out. Plus, expert sleep-tracking tips. Aly Lopez Former Writer I Aly Lopez was a ...