What Is Core Sleep? (Does it Matter?)

Written by Mattress Nerd, Certified Sleep Science Coaches

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In This Article

More and more people are talking about core sleep, but how does it related to REM and deep sleep? Find out here. 

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Sleep is central to good health, yet many people don’t realize how each sleep stage contributes to our mental and physical well-being. Among these stages, “core sleep” stands out as one of the most essential. It encompasses both deep (slow-wave) sleep and REM sleep—the two phases when your body and brain engage in critical tasks such as tissue repair, memory consolidation, and hormone regulation.

What is Core Sleep?

Core sleep is considered the most vital portion of the night, including both the deep sleep stage (where the body focuses on physical restoration) and REM sleep (where the brain processes memories and emotions).

Although deep sleep is part of core sleep, the two terms aren’t interchangeable. Deep sleep primarily addresses physical recovery, whereas core sleep covers both physical and cognitive benefits.

Why Core Sleep Is Important

• Physical Recovery: When you enter deep sleep, your body repairs tissue, strengthens the immune system, and releases growth hormone. This is especially helpful if you’re physically active or an athlete, since it aids muscle recovery.
• Cognitive Function: During REM sleep (the other half of core sleep) your brain consolidates memories, processes information, and boosts problem-solving skills. Without enough REM, mental clarity and decision-making often suffer.
• Emotional Stability: Core sleep also helps regulate mood. Insufficient REM has been linked to stress, anxiety, and a greater risk of depression.

How Much Core Sleep Do You Need?

Most adults need around 7 to 9 hours of sleep each night, aiming for about 3 to 5 hours of core sleep within that window. Several factors can influence how much core sleep you get, including your age, lifestyle, and whether you have any underlying sleep disorders. If you’re consistently waking up feeling unrefreshed, struggling to focus during the day, or noticing more frequent illnesses, it may be a sign of poor core sleep.

How to Improve Core Sleep

• Create an Optimal Environment: Keep the bedroom cool, dark, and quiet to ease the transition into deeper sleep.
• Set a Consistent Routine: Go to bed and wake up at the same time every day, and minimize screen time or bright lights before bedtime.
• Mind Your Diet and Exercise: Limit caffeine and alcohol in the evenings. Stay active, but try not to exercise too close to bedtime. Foods rich in magnesium, such as leafy greens and nuts, can help promote relaxation.
• Track Your Sleep: Wearables like Fitbit, Apple Watch, or Oura Ring can track sleep phases. Various apps can also offer insights and recommendations based on your nightly patterns.

Core Sleep in Polyphasic Schedules

Some people opt for a polyphasic sleep schedule, meaning they break their sleep into several shorter periods throughout the day. However, even these alternate patterns require adequate core sleep. Because some polyphasic approaches significantly reduce core sleep they can lead to insufficient rest and harm overall health.

Final Thoughts

Core sleep underpins much of what makes sleep restorative, encompassing both the body’s deep recovery process and the brain’s memory and emotional regulation.

By making a few small adjustments, like improving your bedroom’s aura and having a consistent bedtime, you can improve your core sleep.

Want to get a better night’s rest? Consider browsing our picks for the best mattresses of 2025.