REM stages and one REM stage. Ideally, you repeatedly cycle through each stage. Learn how long each stage lasts.

Is sleep tracking actually useful in daily life, or is it just data overload distracting you from what matters? After ...

However, data shows that more than 1 in 3 American ... and the same goes for REM sleep. Older adults require less, while babies need much more — in fact, infants can spend about 50% of their ...

Get a deeper understanding of the health metrics your smartwatch measures for you, so you can make full use of them.

On an Apple Watch, "core sleep" is another name for light sleep, which scientists also call stages N1-N2. It is not a type of ...

Need another reason to prioritize your sleep? Not spending enough time in the two deep stages of sleep may hasten the ...

Oxygen re-saturation during sleep is significantly affected by sleep stage and by cardiovascular and pulmonary comorbidities.

Can poor sleep raise your risk of Alzheimer’s? A new study links reduced sleep stages to brain shrinkage in areas prone to ...

While subjective data suggests prior mTBI leads to poorer sleep, there is little objective data to support this association.

Numerous components beyond length of sleep have important ties to cardiometabolic disease and related risk factors.