Sleep Science Guide

The Four Stages of Sleep

A complete sleep cycle is about 90 minutes: N1 (light) → N2 (medium) → N3 (deep) → REM (rapid eye movement). Deep sleep repairs the body; REM consolidates memory. You need 4-6 complete cycles per night.

Why 8 Hours May Not Be Enough?

Sleep needs vary. Some are "short sleepers" (6 hours is enough), others need 9 hours. Quality matters more than quantity — do you wake naturally at the end of a cycle?

How to Assess Sleep Quality?

• Fall asleep speed — within 30 minutes is normal
• Night awakenings — no more than once per night
• Morning feeling — wake naturally without alarm
• Daytime energy — no drowsiness during the day

Science-Based Sleep Tips

Maintain regular sleep schedule, control light exposure (sunlight during day, avoid blue light at night), optimize bedroom environment (18-22°C), avoid intense exercise and heavy meals before bed.

FAQ

Deep sleep vs REM?

Deep sleep handles physical recovery; REM handles memory and emotional regulation.