Sleep Stages and How to Improve Sleep Quality

Lee A. Surkin, MD, outlines the stages of the sleep cycle and some practices that can lead to a better night’s sleep.

Stages of the Sleep Cycleby Lee A. Surkin, MD, FACC, FCCP, FASNC, FAASM

There’s no doubt that sleep is crucial for optimal health. During sleep, the body gets the chance to repair muscles, manage hormones, grow bones, and arrange memories. But sleep duration isn’t the only factor to consider, as many mistakenly believe. Indeed, sleep quality is just as important. So, you have to focus on how many sleep cycles per night your body goes through.

That said, to get high-quality sleep, your body has to go through four to five healthy sleep cycles, each lasting 90 to 120 minutes and consisting of four individual stages. Precisely speaking, a normal sleep cycle includes three non-rapid eye movement (NREM) sleep stages and one rapid eye movement (REM) sleep stage.

The Four Sleep Stages

NREM sleep normally occurs first in adults and includes three stages of which the last one is when the person is in deep sleep (N3) and the individual is unaware of their surroundings and is more difficult to arouse. On the other hand, REM sleep typically occurs an hour to an hour and a half after falling asleep and it is characterized by having the most vivid dreams. Now, let’s discuss the four stages in detail.

Stage 1 – NREM Sleep (N1)

Stage N1 is the transition from being awake to being asleep and typically lasts for only a few minutes. Stage 1 is the lightest stage in a sleep cycle and the person can be easily awakened.


  • Slow eye movements, heartbeat, and breathing
  • Muscles reduce tension and start to relax
  • The brain produces both alpha and theta waves

Stage 2 – NREM Sleep (N2)

Stage N2 comprises the largest percentage of total sleep time. It is still easy to wake up a person from this stage as it is considered to be a lighter one and precedes the stage of deep sleep.


  • No eye movements
  • Heartbeat and breathing at a much slower rate
  • Body temperature decreases
  • The brain produces sleep spindles (bursts of rapid, rhythmic brain activity)

Stage 3 – NREM Sleep (N3)

The last NREM sleep stage N3 is the deepest sleep stage, also known as delta or slow-wave sleep. When a person enters this stage, it is very difficult to wake them up. Stage N3 is vital for many bodily processes for optimal health such as cell regeneration and tissue repair and growth.


  • Still no eye movements
  • Heartbeat and breathing reach the slowest rate
  • The brain produces delta waves

Stage 4 – REM Sleep (R)

Two divisions of REM sleep include phasic (with bursts of rapid eye movements) and tonic (without those bursts). The REM sleep stage lasts about 10 minutes in the first sleep cycle and increases its duration with each upcoming cycle. There are typically 3-5 REM sleep cycles during the sleep period.


  • Rapid eye movements
  • Accelerated heart rate and breathing
  • Paralyzed skeletal muscles with occasional twitches (breathing is diaphragmatic)
  • Increased brain activity

How to Have Healthier Sleep Quality?

Even though having full control over your sleep cycles isn’t possible, certain steps can help you improve your chances of having a healthier sleep quality. One of the key elements to focus on is following good sleep hygiene practices which include the following:

  • Stick to a strict sleep schedule
  • Increase exposure to natural daylight
  • Avoid alcohol and caffeine several hours before bedtime
  • Remove light and noise disruptions at least 2-3 hours prior to planned bedtime
  • Make your bed sleep-friendly and comfortable

We know you take great care of your patients, but do you get quality sleep? If not, consult your doctor to get the right treatment.

Dr. Surkin’s focus in DSP is to increase the solid foundation between the dentist and the sleep physician, and knowing the stages of the sleep cycle can be the first step in recognizing the connection between sleep and wellness. Read more about Dr. Surkin’s connection with DSP as medical editor in chief here:

Stages of the Sleep CycleLee A. Surkin, MD, is the Chief Medical Officer of Nexus Dental Systems. A private practitioner in cardiology, sleep medicine, and obesity medicine, he is one of a small group of physicians to be triple board certified in cardiology, sleep medicine, and nuclear cardiology. In 2009, he created Carolina Sleep – the only dedicated sleep medicine practice in eastern NC. Dr. Surkin has created a cardiovascular and sleep healthcare model that includes a multi-faceted diagnostic and treatment approach that is enhanced by a network of relationships with physicians, dentists, respiratory therapists, sleep technologists, and public officials who recognize the important role that sleep medicine has in our daily life. In 2012, Dr. Surkin founded the American Academy of Cardiovascular Sleep Medicine which is a not-for-profit academic organization dedicated to educating healthcare providers, supporting research, and increasing public awareness of the convergence between cardiovascular disease and sleep disorders. In 2014, Dr. Surkin created a new multi-specialty practice called Carolina Clinic for Health and Wellness which combines his specialties with primary care, gynecology, behavioral health and a medical spa. Dr. Surkin is married with three daughters and a golden retriever and resides in Greenville, NC.

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