Sleep goes through 4 stages N1, N2, N3 and REM, each with its own function, supporting memory consolidation, helping to sleep well, and restore physical and mental health.
Each night’s sleep goes through different cycles, which can last 90-120 minutes, including 4 stages. In which, REM is rapid eye movement sleep, N1, N2 and N3 are three non-rapid eye movement stages (non-REM sleep, also known as NREM).
MSc. Hoang Chau Bao Dinh, specialist in Neurology, Tam Anh General Clinic, District 7, Tam Anh General Hospital, Ho Chi Minh City, said each stage of sleep has its own function. NREM usually accounts for about 75% of sleep time each night, playing a role in consolidating memory and supporting physical health recovery. REM accounts for about 25% of nighttime sleep, helping to improve cognitive and emotional health.
Stage N1: Light sleep appears in the first 1-5 minutes, up to 10 minutes in people with insomnia or difficulty sleeping, accounting for 5% of sleep time each night. At this time, the body is in a sleepy, dreamy state, eye movements and breathing gradually slow down, blood pressure and blood flow to the brain begin to decrease, and muscles relax more. People in N1 light sleep are still aware of some things going on around them, so they are easily startled or awakened.
Stage N2: Deep sleep usually lasts 10-25 minutes during the first cycle and after each sleep cycle. This stage usually accounts for more than 45% of a normal person’s total sleep time. In stage N2, the body moves into a more relaxed and relaxed state. Brain waves begin to slow down, body temperature decreases, muscles relax, breathing and heart rate slow down.
Stage N3: Sleep is very deep and most difficult to awaken. A normal person will spend about 20-40 minutes for an N3 stage. In the first cycle of the night, the N3 phase lasts the longest, and in the following cycles it will become increasingly shorter. At this time, the body is almost completely relaxed and relaxed, muscle tone, pulse, and breathing rate decrease more. This is the time for the body to recover, repair damaged cells, strengthen the immune system, and regenerate energy. The end of N3 is also the end of the three non-REM (NREM) periods.
REM stage: The rapid eye movement stage, also known as the dream sleep stage, usually accounts for about 25% of sleep in adults, appearing after about 90 minutes of sleep. The REM stage of the first sleep cycle may only last a few minutes, but later cycles are longer, up to 60 minutes.
At this time, brain wave activities are similar to when awake. This may be the reason for the formation of dreams. At this time, heart rate, blood pressure and breathing increase again. Muscle activity is minimally inhibited, except for the eyes and the muscles that control breathing. The important role of REM is to improve the brain’s ability to learn and remember because at this time the brain processes, consolidates, and remembers information.
Doctor Bao Dinh said that when the sleep cycle goes through all 4 stages, it will automatically repeat a new cycle until the end of the sleep period. The average nightly sleep time of adults is about 7-9 hours. Children under one year old should sleep 12-16 hours a day, children 1-5 years old should sleep 11-14 hours. From 6-12 years old, children can reduce it to 9-12 hours. Teenagers 13-18 years old need 8-10 hours of sleep every night.
People with symptoms of sleep disorders such as poor sleep, loud snoring, frequent difficulty sleeping, insomnia, fatigue… should be examined and treated promptly at a Neurology department. Patients can have polysomnography to check and support the diagnosis of related diseases and timely treatment.
To have quality sleep stages, do not drink alcohol or use psychoactive substances, and avoid eating and drinking two hours before bedtime. Work and rest in moderation and scientifically to reduce stress and relax. Maintain good sleep hygiene and exercise regularly.
Doctor Dinh said children 12 years and older and adults can use natural essences from blueberry and ginkgo biloba. They contribute to increasing blood flow to the brain, improving nerve function, helping reduce stress, headaches, and improving sleep quality.