Modern sleep science offers several evidence-based explanations for why people often wake during the pre-dawn hours.
### Sleep Cycle Transitions
Human sleep follows repeating **90-minute cycles** that move through stages including:
* Light sleep
* Deep sleep
* REM (dream sleep)
Between **3 and 5 a.m.**, many people naturally transition into **lighter sleep stages**, which makes waking up much more likely—especially if stress or noise interrupts the cycle.
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### Cortisol Rhythm
Your body follows a natural hormone rhythm called the **Circadian Rhythm**.
As part of this rhythm, the hormone **Cortisol** begins rising around **3–4 a.m.**. Cortisol helps prepare the body to wake up and become alert.
