Sleep is a naturally reoccurring altered state of consciousness and a periodic state of rest for mind and body characterised by decreased awareness, decreased bodily movements and responsiveness to external stimuli.
Stages of Sleep
• Stages 1 to 3 – rapid eye movement (NREM) sleep or quiet sleep.
• Stage 4 – rapid eye movement (REM) sleep, or active sleep or paradoxical sleep.
NREM Stage 1
It is a ‘dozing off’ stage. It is a transition period between wakefulness and sleep which normally lasts for just 1-5 minutes.
If someone is awaken during this stage, they might report that they were not asleep.
During stage 1 sleep:
• The body hasn’t fully relaxed, hence if you awake someone during this stage, they may report they were not asleep.
• Brain activities slow down.
• Heartbeat, eye movements, and breathing slow with it.
It is easy to wake someone up during this stage as in this stage body and brain hasn’t fully relaxed, but if a person isn’t disturbed during this stage they can move quickly into stage 2
NREM Stage 2
People spend approximately half of their total sleep time in NREM stage 2. It lasts for about 20 minutes per cycle.
As per the American Sleep Foundation, individuals spend around half of their total sleep time during NREM stage 2, which goes on for around 20 minutes for each cycle.
During stage 2 sleep,
• The body enters into a subdued state and becomes less aware of the surroundings.
• Body temperature drops
• Eye movements stop
• Heart rate and breathing becomes regular
• In this stage, the brain activity slows down, but the presence of short bursts of activity help oppose being woken up by external stimuli.
NREM Stage 3
This stage is also known as deep sleep, delta sleep or short wave sleep (SWS) in which body starts its physical repairs and meanwhile, brain consolidates declarative memories like personal experiences, facts, general knowledge and other learned things. It is harder to wake someone up if they are in this phase as any noises or activity in the environment fail to wake the sleeping person.
Getting enough sleep in this stage allows us to feel refreshed the next day.
During NREM stage 3 sleep:
• Body and muscles are completely relaxed
• Blood pressure drops and breathing slows
• Progress into your deepest sleep
Importance of stage 3
• Allows bodily recovery and growth
• Boosts immunity
• Contributes to thoughtful thinking, creativity and memory.
The most time spend in deep sleep is during the first half of the night. During the early sleep cycles, it probably lasts for 20-40 minutes. As the sleep progresses, these stages get shorter, and more time gets spent in REM sleep.
REM Sleep
In REM sleep
• Brain lights up with activity
• Body is relaxed and immobilized
• Breathing is faster and irregular
• Eyes move rapidly
• Dream
During REM sleep, brain activity picks up, approaching levels seen when we’re awake. Simultaneously, the body encounters atonia, which is a temporary paralysis of the muscles (except 2 muscles – the eyes and the muscles that control ). Despite the fact that the eyes are closed, they can be seen moving quickly, which is how this stage gets its name.
Importance of REM sleep
• Essential for memory, learning, and creativity.
• Known for the most vivid dreams.
Normally we don’t enter a REM sleep stage until we’ve been asleep for about 90 minutes. As the night progresses, REM stages get longer, particularly in the second half of the night. The first REM stage last only a few minutes, while later stages can last for around an hour. REM , in total make up around 25% of sleep in adults.
Sequence of sleep stages
Sleep does not advance through the 4 stages in perfect sequence.
When we have a full night of uninterrupted sleep, the stages progress as follows:
1. Sleep begins with NREM stage 1 sleep which progresses into NREM stage 2 followed by NREM stage 3, then NREM stage 2 is repeated and then the finally, we’re in REM sleep
Once REM sleep is finished, the body normally gets back to NREM stage 2 before starting the cycle all over again.
Recommended amount of sleep for children
The American Academy of Pediatrics recommends:
| Child’s age | Recommended sleep time in 24 hours |
| Infants 4 to 12 months | 12 to 16 hours including naps |
| Children 1 to 2 years | 11 to 14 hours including naps |
| Children 3 to 5 years | 10 to 13 hours including naps |
| Children 6 to 12 years | 9 to 12 hours |
| Teenagers 13 to 18 years | 8 to 10 hours |
Sleeping time according to age of child
| Age ( in years ) | Sleeping time |
| 5 | 6:45 p.m. – 8:15 p.m. |
| 6 | 7:00 p.m. – 8:30 p.m. |
| 7 | 7:15 p.m. – 8:45 p.m.. |
| 8. | 7:30 p.m. – 9:00 p.m. |
| 9 | 7:30 p.m. – 9:15 p.m. |
| 10 | 8:00 p.m. – 9:30 p.m. |
| 11 | 8:15 p.m. – 9:45 p.m. |
| 12 | 8:15 p.m. – 9:45 p.m. |
Importance of sleep
• Sleep promotes growth
• Increases child’s attention span
• Boosts learning and memory
• Kids become more creative
• Child have better problem-solving abilities
• They have more energy during the day.
How does sleep affect brain development?
•Most of child’s brain development happens during sleep as it is when the connections between the left and right hemispheres of their brains are being formed.
•Brain synapses are formed during sleep. More than 1,000,000 million neural connections are formed per second during their initial 3 years.
•Memories are formed and stored: Baby’s brain stores what they’ve discovered and learned in the day during their sleep.
•Lack of sleep can cause cognitive issues, developmental delays, etc.
•Besides the impact sleep has on child’s growing brain, it likewise impacts child’s mood, eating, behaviour, etc.
Sleep hygiene
It refers to our sleep environment and sleep-related habits.
1. Routine – Try achieving a more consistent sleep schedule
• A routine can start 30 minutes to an hour before bedtime, and can include activities like a warm shower or reading a story.
• Going to the toilet should be the last task before getting into bed.
2. Environment – Pleasant and relaxing sleep environment ( mattress, pillow, sheets, etc. )
• It should be a place where they feel safe and secure.
3. Exercise – Children may face difficulty in falling asleep if they have been inactive throughout the day.
• Encouraging them to play outside or just go for a walk in the fresh air.
• Avoid exercise directly before bedtime.
4. Food – Avoid large meal before bedtime and have a glass of warm milk before sleep.
• avoiding stimulants ( caffeine – tea, coffee ) before bedtime
• Prefer to eat early.
5. Technology – Avoid use of electronic devices such as TV, mobile phones etc. before bedtime.
6. Get enough natural daylight exposure.
7. Eliminating noise and light disruptions.
Dr C P Ravikumar
CONSULTANT – PEDIATRIC NEUROLOGY
Aster CMI Hospital, Bangalore