How does sleep work ?

What is the sleep cycle?

Imagine sleep as a journey through a series of rhythmic stages, each with its own role in recovering our bodies. Here’s a simple table to break down these stages and the approximate time it takes to reach each:

Stage	Time to reach	Description
Light Sleep	5-10 minutes	The entry point into sleep, easy to awaken
Deep Sleep	35-45 minutes	The restorative sleep, hard to be awakened
REM Sleep	70-90 minutes	The dream stage, where brain activity peaks

As we cycle through these stages, our body performs critical maintenance to repair muscle, consolidate memory, and release growth hormones.

What is Non-REM sleep?

Non-REM sleep comprises about 75% of our nightly sleep cycle and is divided into three stages:

• Stage 1: This initial phase is the gateway between wakefulness and sleep, lasting just a few minutes. It's the lightest phase, where we can be easily disturbed.
• Stage 2: We begin to disengage from our surroundings, our body temperature drops, and our heart rates slow. This stage prepares us for deep sleep.
• Stage 3: The deep, restorative sleep that helps recover our body, heal tissues, and boost immune functions.

Each of these stages serves as a building block for our overall health, supporting everything from mental clarity to physical vitality.

Deep sleep

What is deep sleep?

Deep sleep, also known as slow-wave sleep, is the stage where our body and brain waves slow down dramatically. It's like the calm at the center of a storm, where external noises and disturbances become less likely to wake us. This stage is characterized by delta waves, which are the slowest and highest amplitude brain waves. During deep sleep, our brain is less responsive to external stimuli, making it the most recovering phase for physical and mental recovery.

When is deep sleep?

Deep sleep generally occurs in longer periods during the first half of the night, as part of the earlier sleep cycles. Typically, we enter deep sleep about 35 to 45 minutes after falling asleep. As the night goes on, periods of deep sleep shorten, and then comes the REM (rapid eye movement) sleep. This distribution means that disruptions in early night sleep can significantly reduce the quality of deep sleep, impacting overall restfulness and recovery.

Why is deep sleep important?

Deep sleep is crucial for multiple reasons, serving as the core of our nightly recovery by supporting intense physical and mental restoration. Here's why it's essential:

• Physical health: Deep sleep facilitates the repair of tissues, and the building of bone and muscle. It also strengthens the immune system and is the prime time for releasing growth hormones, essential for daily recovery.
• Mental health: This stage is vital for memory consolidation and information processing, supporting key cognitive functions like learning and memory. Adequate deep sleep is necessary for brain readiness for the next day's challenges.
• Emotional well-being: Deep sleep significantly influences emotional stability. Insufficient deep sleep is linked to mood fluctuations and increased anxiety, playing a key role in emotion regulation and stress management.
• Detoxification: During deep sleep, the brain's glymphatic system is more active, efficiently clearing out neurotoxic waste that accumulates during the day, including beta-amyloid, thus helping prevent neurodegenerative diseases.

Sleep's longest stage

Interestingly, the stage that lasts the longest overall during the night is usually the stage 2 of sleep, especially in the first sleep cycles. As the night progresses, REM sleep periods lengthen, making up a significant portion of the late sleep hours. Each stage has its symphony to play, ensuring that by morning, you're refreshed and ready to wake up.

As we move deeper into the night, the dynamic shifts from stage 2 to longer periods of REM sleep. This stage, rich in dreams, plays a crucial role in mental health by facilitating brain processes involved in learning and memory. Imagine REM sleep as the night's grand finale—vivid, intense, and memorable, setting the stage for a refreshing morning. This complex balance ensures we don’t only rest but also restore and recover our minds and bodies effectively.