Understanding Sleep Cycles
Sleep isn't uniform—it progresses through distinct stages in approximately 90-minute cycles. Aligning your sleep schedule with these cycles helps you wake feeling refreshed rather than groggy.
The Sleep Cycle Stages
- Stage 1 (Light Sleep): Transition phase, easily awakened (5-10 min)
- Stage 2 (Light Sleep): Heart rate slows, body temperature drops (20 min)
- Stage 3 (Deep Sleep): Restorative sleep, hardest to wake from (20-40 min)
- REM Sleep: Dreams occur, brain is active, muscles paralyzed (10-60 min)
Why Timing Matters
Waking during deep sleep (Stage 3) causes "sleep inertia"—that groggy, disoriented feeling. By timing your alarm to the end of a sleep cycle, you wake during lighter sleep stages and feel more alert.
Recommended Sleep Duration
| Age Group | Recommended Hours |
|---|---|
| Adults (18-64) | 7-9 hours (5-6 cycles) |
| Older Adults (65+) | 7-8 hours |
| Teenagers (14-17) | 8-10 hours |
| Children (6-13) | 9-11 hours |
Sleep Hygiene Tips
- Keep a consistent sleep schedule, even on weekends
- Avoid screens 1 hour before bed (blue light suppresses melatonin)
- Keep your bedroom cool (65-68°F / 18-20°C)
- Avoid caffeine 6+ hours before bedtime
- Get sunlight exposure during the day to regulate circadian rhythm