Why Do We Sleep? What Happens During Sleep?

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Why Do We Sleep? What Happens During Sleep?

The Importance of Sleep

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Sleep gives your body, including your brain, time to repair itself and carry out important functions, like clearing out waste and releasing hormones. It is essential for good health. In fact, we need sleep to survive — just like we need food and water. So, it’s no wonder we spend about one-third of our lives sleeping.

Many Biological Processes Happen During Sleep

The brain stores new information and gets rid of toxic waste. Nerve cells communicate and reorganize, which supports healthy brain function. The body repairs cells, restores energy, and releases molecules like hormones and proteins. These processes are critical for our overall health. Without them, our bodies can’t function correctly.

What Happens During Sleep

During sleep, your body cycles through four stages of sleep. This cycle occurs multiple times throughout the night for different lengths of time, varying from 70 to 120 minutes each. The stages generally repeat about four to five times during a 7- to 9-hour sleep period.

The pattern includes two major phases of sleep: non-rapid eye movement (non-REM) sleep and rapid eye movement (REM) sleep. The four stages of sleep include three stages of non-REM sleep and one stage of REM sleep.

• Stage 1: Non-REM Sleep: This stage occurs when you first fall asleep. As your body enters light sleep, your brain waves, heart rate, and eye movements slow down.
• Stage 2: Non-REM Sleep: This stage involves the light sleep just before deep sleep. Your body temperature decreases, your eye movements stop, and your heart rate and muscles continue to relax.
• Stage 3: Non-REM Sleep: In stages 3 and 4, deep sleep begins. Your eyes and muscles don’t move, and your brain waves slow down even further. Deep sleep is restorative. Your body replenishes its energy and repairs cells, tissues, and muscles.
• Stage 4: REM Sleep: This stage first happens about 90 minutes after you fall asleep. Your eyes move quickly from side to side during REM sleep. In REM sleep, your brain waves and eye movements increase. Your heart rate and breathing also speed up.

Recommended Amount of Sleep

The recommended amount of sleep depends on your age. The CDC suggests the following durations based on age:

• Birth to 3 months: 14 to 17 hours
• 4 to 12 months: 12 to 16 hours per 24 hours, including naps
• 1 to 2 years: 11 to 14 hours per 24 hours, including naps
• 3 to 5 years: 10 to 13 hours per 24 hours, including naps
• 6 to 12 years: 9 to 12 hours
• 13 to 18 years: 8 to 10 hours
• 18 to 60 years: 7 or more hours
• 61 to 64 years: 7 to 9 hours
• 65 years and older: 7 to 8 hours

Consequences of Sleep Deprivation

Without enough sleep, your body has a hard time functioning properly. Sleep deficiency is linked to chronic health problems affecting the heart, kidneys, blood, brain, and mental health. Lack of sleep is also associated with an increased risk of injury for both adults and children.

Specific consequences of sleep deprivation can include:

• Poor memory and focus
• Weakened immunity
• Mood changes
• Driver drowsiness, which can contribute to serious car accidents and even death
• Increased risk of falls and broken bones in older adults

Why We Sleep

Sleep is still not fully understood, but scientists think it serves many purposes. One theory is that sleep helps the body conserve energy. Sleeping allows us to reduce our caloric needs by spending part of our time functioning at a lower metabolism. The way our metabolic rate drops during sleep is backed by research.

Another theory is that sleep helps the body restore itself. The idea is that sleep allows cells to repair and regrow. This is supported by many important processes that happen during sleep, including:

• The brain plasticity theory says sleep is required for brain function. It allows your neurons, or nerve cells, to reorganize.
• The restorative theory says the body needs sleep to repair itself.

FAQs

Q: How much sleep do I need?

A: The recommended amount of sleep varies by age, but most adults need 7 to 9 hours of sleep each night.

Q: What happens during sleep?

A: Your body cycles through four stages of sleep, including non-REM sleep and REM sleep.

Q: What are the consequences of sleep deprivation?

A: Sleep deprivation is linked to chronic health problems and an increased risk of injury for both adults and children.

Q: Why do we sleep?

A: While the exact causes aren’t clear, scientists think sleep helps the body conserve energy and restore itself.