Healthy sleep is more important than you may think. In fact, an ongoing lack of quality sleep can affect a person’s ability to function day to day and perform well at work or school. Low quality sleep is also linked with chronic diseases and conditions that threaten overall health – such as type 2 diabetes, heart disease, obesity, and depression.

To avoid unfavorable health consequences, the Centers for Disease Control and Prevention (CDC) recommends that adults receive 7-9 hours of sleep per night. Despite the importance of quality sleep, one in three adults report that they usually get less than the daily-recommended amount. While sleep duration is important, it is also essential to consider sleep quality. To get sleep that is restorative, you want to smoothly progress through sleep cycles, so you are not left feeling tired the next day, regardless of how many hours you slept.

The sleep cycle is composed of four individual stages and in a typical night, you will experience 4-6 sleep cycles that last on average, 90 minutes each. The four stages of sleep are determined by specific brain wave activity and there are two basic types of sleep: rapid eye movement (REM) sleep and non-REM sleep (which has three different stages).

Stage 1 / N1 non-REM sleep is the changeover from wakefulness to sleep – think of this as the dozing off period. This stage lasts only a few minutes, in which your heartbeat, breathing, eye movements, and brain activity begin to slow down and transition from daytime wakefulness.

Stage 2 / N2 non-REM sleep lasts between 10-25 minutes during the first sleep cycle but gradually extends as you progress through your nightly sleep. As the body temperature drops and eye movements stop, you enter a deeper sleep. During N2 sleep, brain activity slows overall but there are brief bursts of electrical activity. You will spend more time in stage 2 sleep than any other stage collectively throughout the night.

Stage 3 / N3 non-REM sleep is an important period of deep sleep that your body requires to feel refreshed in the morning. During N3 sleep, your heartbeat and breathing slow to their lowest levels during the night and it is more difficult to wake someone up during this phase. Sleep experts believe that this stage is vital for restorative sleep, allowing for bodily recovery, immune system support and growth.

REM sleep occurs approximately 90 minutes after falling asleep and is marked by rapid eye movements from side to side (hence the name, rapid eye movement sleep). Brain activity increases, nearing waketime levels and the heartrate and breathing accelerate. Arm and leg muscles enter temporary paralysis to keep you from acting out vivid dreams that occur during this phase. Experts believe that REM sleep is an important component for learning, memory, and creativity.

Sleep stages are important because they have a profound effect on sleep quality. If you are waking frequently through the night, have a sleep disorder such as sleep apnea or restless leg syndrome, or have an uncomfortable sleeping environment, you may experience excessive daytime sleepiness. It is important that you take steps to improve underlying issues so you can achieve restorative sleep. If you find that you are struggling to get healthy sleep, do not hesitate to speak with your doctor about factors that influence the amount of sleep you get each night so you can stay in good physical and mental health.


The Sleep Wellness Center at Island Hospital is devoted to helping adult and pediatric patients achieve the sleep they need to improve their lives and health. For more information, call (360) 299-8676.

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Published on March 18, 2021