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Sweet Dreams and Rejuvenation: What Actually Happens During the Sleep Cycle

March 11, 2019Jennifer Roszkowski

Do you ever wonder why you wake up feeling well-rested some mornings, and others like you’re in a fog? It may have to do with what stage of the sleep cycle you awoke from, or how many cycles you completed throughout the night.

In support of Sleep Awareness Week, Jennifer Roszkowski, DO, explains the stages of the sleep cycle and why they’re so important.

The sleep cycle, which lasts for about 90 minutes, is comprised of four unique stages: N1, N2, N3 (all non-rapid eye movement stages) and REM (rapid eye movement).

N1, the lightest stage, accounts for around 5 percent of the sleep cycle.

“During this stage, your body starts to slow down, including your heart rate, your breathing and eye movement,” Dr.Roszkowski said. “Your muscles are not yet relaxed, so it’s normal to experience minor twitching.”

N2 is the longest stage in the sleep cycle, accounting for about 50 percent of the time. This is the onset of sleep.

“This is when you disengage from your surroundings,” explained Dr. Roszkowski. “Your body temperature drops, your breathing and heart rate regulate, your eye movement stops, and your brain activity slows.”

N3, which is the deepest stage of the cycle and accounts for about 15 to 20 percent of the time, is the most restorative stage. Muscle and tissue growth and repair occurs, energy is restored and the immune system is strengthened.

“Have you ever had someone wake you up in your sleep, and you started swatting at them, because you’re scared and disoriented,” asked Dr. Roszkowski. “This means you were in stage N3. You’re much less responsive to the environment, your blood pressure lowers, and your muscles relax.”

“Also important in this stage is the regulation of the hunger hormone, leptin, which suppresses appetite,” Dr. Roszkowski continued.

REM sleep, which accounts for about 20 to 25 percent of the sleep cycle, is commonly known for its vivid dreams. However, REM sleep also plays an important role in learning and memory retention, and, like N3, is highly energizing.

“The only two muscles that are really alert during this stage are your eyes and your diaphragm,” said Dr. Roszkowski. “Your body is immobile, but your heart rate, breathing, and blood pressure actually all increase.”

According to Dr. Roszkowski and many other experts, the ideal, healthy night’s sleep is to complete the sleep cycle 4 to 5 times. When we are deprived of this, whether it is from health conditions or external factors, we suffer.

“It’s common to feel unfocused, get headaches and even experience muscle aches (because the repair never occurred during N3),” Dr. Roskowski explained. “Patients describe their mindset as clouded. It’s extremely hard to function this way.”

“Patients with sleep apnea or insomnia have difficulty reaching those deeper, restorative stages,” said Dr. Roskowski. “They may not even dream at all during the night.”

Of course, consuming anything high in caffeine or sugar close to your bedtime is not going to allow you to have quality sleep. Drinking alcohol is also detrimental, because it causes a lot of awakenings during the second half of the sleep cycle, resulting in very little REM sleep.

Everyone experiences a unique sleep, so one environment might work for somebody else but not for you. If you’re experiencing difficulty sleeping, try a nice, quiet, dark environment, and turn off the screens. Darkness activates the hormone melatonin, which will increase your drive to want to sleep. If changing these external factors does not help, be sure to tell your doctor.

To learn more about Pulmonary & Sleep Medicine services offered at Jefferson Health in New Jersey, click here.