Sleep
Cycles
90-Min Cycles · Optimal Bedtimes · Wake Refreshed
Sleep Cycle Science
| Stage | Duration | What Happens |
|---|
| Stage 1 (Light) | 5-10 min | Drifting off, easily awakened |
| Stage 2 (Light) | 20 min | Heart rate slows, temp drops |
| Stage 3 (Deep) | 20-40 min | Body repair, growth hormone |
| REM Sleep | 10-60 min | Dreaming, memory consolidation |
One full cycle = ~90 minutes. Waking between cycles (not during deep sleep) is key to feeling refreshed.
Sleep by Age
| Age | Recommended | Cycles |
|---|
| Newborn (0-3 mo) | 14-17 hours | Irregular |
| Toddler (1-2 yr) | 11-14 hours | 7-9 cycles |
| School age (6-13) | 9-11 hours | 6-7 cycles |
| Teen (14-17) | 8-10 hours | 5-6 cycles |
| Adult (18-64) | 7-9 hours | 5-6 cycles |
| Senior (65+) | 7-8 hours | 5 cycles |
Tips to Fall Asleep Faster
| Tip | Why |
|---|
| No screens 30 min before bed | Blue light suppresses melatonin |
| Cool room (65-68°F / 18-20°C) | Core temp drop signals sleep |
| Same time every day (weekends too) | Trains circadian rhythm |
| No caffeine after 2 PM | Half-life is 5-6 hours |
| 4-7-8 breathing technique | Activates parasympathetic system |