When you first look at your sleep tracker data, all those numbers and graphs can feel dizzying ... categories of sleep: REM, deep and light, although you actually cycle through five stages ...

More sleep! Better sleep! Deeper sleep! It's what we all want, right? If your New Year's resolution is to get better at—well—sleeping, your problem might be core sleep. While some people may find it ...

Yet for many of us, waking frequently throughout the night is perfectly normal ... that an adult sleep cycle usually lasts around 90 minutes. “During this time we dip into deep sleep and ...