Stages of Sleep

Sleep is essential for physical health, mental clarity, and emotional balance. Most sleep experts agree that sleep occurs in four stages of sleep, and your body cycles through these stages multiple times each night. Understanding the stages of sleep can help improve sleep quality and overall well-being.

According to the National Library of Medicine, the sleep cycle includes both non-REM sleep and REM sleep, and each stage plays a vital role in rest and recovery.

Stage 1: Light Sleep

The lightest of the stages of sleep occurs as you begin to fall asleep. Brain activity slows, muscles relax, and breathing remains steady. You can wake up easily during this stage. It can lasts 1 to 5 minutes and makes up about 5% of total sleep.

Stage 2: Deeper Sleep (Non-REM)

It is not deep sleep yet. During this stage, heart rate slows and body temperature drops. This stage is essential for memory consolidation and brain health. The first cycle lasts about 25 minutes, and later cycles become longer. Stage 2 accounts for approximately 45% of total sleep.

Stage 3: Deepest Sleep (Non-REM)

It is difficult to wake from deepest sleep, and waking during this stage often causes grogginess that can last 30 minutes to one hour. Deep sleep supports muscle repair, immune function, and brain recovery. It is also the stage linked to sleepwalking, teeth grinding, and night terrors. Stage 3 makes up about 25% of sleep.

Stage 4: REM Sleep

Know as rapid eye movement sleep, is the stage when most dreaming occurs. Brain activity increases, and breathing becomes irregular. It usually begins about 90 minutes after falling asleep. The first REM cycle lasts around 10 minutes, while the final cycle can last up to one hour. REM sleep supports learning, memory, and emotional regulation and accounts for roughly 25% of total sleep.

Why the Stages of Sleep Matter

Each of the stages of sleep serves a unique purpose. Together, they support physical repair, cognitive function, and emotional health. Disruptions to the sleep cycle can reduce sleep quality and impact long-term health.

Learning how the sleep cycle works can help you build healthier sleep habits and improve overall wellness.

RESOURCES:

National Library of Medicine, Physiology, Sleep Stages, Aakash K Patel, Vamsi Reddy, Karlie R Shumway, John F Araujo, January 26, 2024
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Kaiser Permanente, Stages of Sleep, Ignite Healthwise, LLC Staff, July 31, 2024
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Sleep Foundation, Stages of Sleep: What Happens in a Sleep Cycle, Eric Suni, Medically Reviewed Dr. Abhinar Singh, December 8, 2023
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Last viewed: 20250309