1# Why We Sleep: Key Findings23Sleep is the single most effective thing we can do to reset our brain and body.45## Sleep Architecture6- NREM Stage 3 (deep sleep): physical restoration, immune function7- REM: emotional processing, creativity, memory consolidation8- Each cycle ~90 min, 4-5 cycles per night ideal910## The Cost of Sleep Debt11- After 1 week of 6h/night: cognitive performance equals 0.05% BAC12- Chronic sleep debt linked to Alzheimer’s — glymphatic clearance drops 60%13- 5h sleep → testosterone drops 10–15% in healthy young men1415## Practical Sleep Hygiene16- Optimal bedroom temperature: 18–19°C17- No blue light 90 min before bed — melanopsin sensitivity peaks at 480nm18- Caffeine half-life 6h: last intake before 2pm19- Wake-time consistency matters more than bedtime consistency2021## Open Questions22- Do naps compensate for night debt? Evidence mixed23- Melatonin: 0.3mg as effective as 3mg. Most supplements are overdosed.
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