How Much Deep Sleep Do You Actually Need?
Deep sleep makes up roughly 13 to 23 percent of a healthy adult’s night, and it declines with age. Here is what that means for the number on your tracker.
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How Caffeine Affects Sleep (And When to Stop Drinking It)
Caffeine does not just keep you awake longer. It reduces deep sleep, and the effect is measurable eight hours after your last cup. Here is what the research shows and how to work out your own cut-off time.
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Why You Wake Up at 3 AM (And What to Do About It)
Waking in the small hours is usually not a sleep disorder. It is what happens when a normal light sleep phase meets a body that has been primed to wake — by alcohol, blood sugar, temperature or worry.
