Question 1

What is the 90-minute sleep cycle?

Accepted Answer

The 90-minute sleep cycle (ultradian rhythm) is the natural pattern of sleep. Each complete cycle includes light sleep, deep sleep, and REM (rapid eye movement) sleep. Adults typically experience 4-6 cycles per night. Waking up at the end of a cycle leaves you feeling most refreshed.

Question 2

How many hours of sleep do I need?

Accepted Answer

Most adults need 4-6 complete sleep cycles (6-9 hours). The optimal amount varies by individual. The key is completing full cycles rather than hitting a specific hour count. Start with 5 cycles (7.5 hours) and adjust based on how you feel.

Question 3

Is it really better to wake up at cycle end?

Accepted Answer

Yes. Waking up at the end of a sleep cycle (REM or light sleep phase) when your brain is already near wakefulness leaves you feeling alert and energized. Waking during deep sleep causes sleep inertia - grogginess and slow thinking.

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