Learn about the sleep cycle stages

Ever wonder what your body does when you’re sleeping?

While you’re asleep, your body typically goes through several sleep cycles that lasts on average 90 minutes. The typical cycle has two phases: Non-Rapid Eye Movement Sleep (NREM Sleep) which includes Light Sleep and Deep Sleep, as well as Rapid Eye Movement Sleep (REM Sleep).

Light Sleep (N1 and N2)

Light sleep serves as the entry point into sleep each night as your body unwinds and slows down. This stage typically begins within minutes of falling asleep. During the early part of light sleep, you may drift between being awake and asleep. You may be somewhat alert and can be easily awoken. Breathing and heart rate typically decrease slightly during this stage. Light sleep promotes mental and physical recovery.

Deep Sleep (N3)

When you wake up feeling refreshed in the morning, you’re likely to have experienced solid periods of deep sleep. During deep sleep, it becomes harder to be awakened since your body becomes less responsive to outside stimuli. Breathing becomes slower and muscles relax while heart rate usually becomes more regular. Deep sleep promotes physical recovery, memory and learning. This stage has also been shown to support your immune system.

How many hours of deep sleep do you need?

Most adults should aim for seven to nine hours of sleep each night. Between 13-23% of that time should be spent in deep sleep. If you get seven hours of sleep each night, then you spend approximately 55 to 97 minutes each night in deep sleep. Scientists agree that while stages 1 to 4 and REM sleep are all important, deep sleep is the most essential of all for feeling rested and staying healthy.

REM Sleep (N4)

The first phase of REM sleep typically occurs after you’ve had an initial stage of deep sleep. You generally stay in REM sleep for a longer period of time during sleep cycles occurring in the second half of the night. During this final stage of sleep, your brain becomes more active. Dreams mainly occur during REM sleep, and your eyes move quickly in different directions. Heart rate increases and breathing becomes more irregular. REM sleep has been shown to play an important role in mood regulation, learning, and memory as your brain processes and consolidates information from the previous day so that it can be stored in your long-term memory. For healthy adults, spending 20-25% of your time asleep in the REM stage is a good goal.

Wrapping up, it’s crucial to recognize sleep as a complex, dynamic process, rather than merely a passive period of rest. During a sleep cycle, it’s most common to go from light sleep to deep sleep, back to light sleep, and then into REM sleep. Then the cycle generally repeats, but sleep patterns vary naturally. Understanding and achieving a balance of these stages is a key to not just more sleep, but better quality sleep, underpinning our overall health.