Why is it that some mornings are more difficult to get up from than others? If you’ve ever felt this way, know you are not alone. The reality is our sleep cycles may actually play a role in this phenomenon.
Although sleep seems to pass quickly and your body appears to be at rest, quite a bit of activity occurs during the night. When we sleep, our bodies cycle between four different stages of sleep, which fall under either non-rapid eye movement (NREM) sleep or rapid eye movement (REM).
Let's take a look at what these sleep cycles are, what occurs during each one, and why they're important.
What are sleep cycles?
Sleep cycles are fluctuations between the NREM and REM phases of sleep – also referred to as the ultradian sleep cycle, sleep-dream cycle, and REM-NREM cycle. During each cycle, we experience three stages of NREM sleep and one stage of REM sleep, and each cycle lasts around 90 minutes.
Let's jump into what each stage of our sleep looks like.
Stage 1
Stage 1 or N1, is the first stage of NREM sleep we experience. This first stage is essentially when we begin to fall asleep and can last anywhere from one to five minutes.
During stage 1, our body winds down as we get ready to move through the sleep cycles. This stage of sleep is the lightest sleep we experience. If you wake up during this stage, you may feel as if you haven't slept at all.
Stage 2
Stage 2 sleep cycles are characterized by a drop in body temperature, breathing, and heart rate as our body and muscles begin to relax.
As brain activity slows down in stage 2, we experience short bursts of rapid waves, called sleep spindles, which help us from being woken up by external stimuli.
Stage 2 lasts between 10-25 minutes and each stage 2 cycle lasts longer after its first initial cycle.
Stage 3
The final stage of NREM sleep we experience is stage 3. Our body falls deeper into sleep and will not be as easily woken during this stage. As we relax into sleep, our muscle tone, pulse, and breathing rate slow down, and no eye movement or muscle activity is experienced.
This stage plays a key role in experiencing restorative sleep, which is critical for recovery and growth. Evidence suggests that deep sleep, like the sleep we experience in stage 3, strengthens our ability to think critically, and creatively, and helps support our memory.
Stage 4
Stage 4 is when we enter REM sleep, brain activity increases and results in lighter sleep cycles than stage 3. If you’ve ever experienced intensely vivid dreams, you most likely experienced them during this stage of sleep. Our brain activity level resembles levels we experience while we’re awake, which is what contributes to vivid dreams.
REM sleep usually begins around 60-90 minutes after falling asleep. The first REM period is usually around 10 minutes, with each stage getting longer after the first cycle.
Notably, the amount of REM sleep we experience is highest during our infancy. It begins to decline in adolescence and young adulthood and then takes another decline later into adulthood.
Why are sleep cycles important?
Simply put, sleep cycles and their stages are important because they offer the brain and body the necessary time it needs to recover and develop. We may not be able to directly control our sleep cycles, but we can take steps to enhance them by ensuring our sleep environment is conducive to a comfortable night's sleep. This includes having the best mattresses, pillows, sheets, and sleep routine possible.
At MLILY, we’re here for you during every stage of life and every cycle of sleep. We've devoted time and research to crafting industry-leading proprietary foams and materials to ensure you achieve the most restorative night’s sleep possible. Shop MLILY for better sleep and a better life.