Sleep Architecture — What a Good Night Looks Like

Sleep is not uniform. A normal night cycles through 4-6 complete cycles of ~90 minutes each: NREM STAGE 1 (5-10 min): Light sleep. Hypnic jerks. Easy to wake. NREM STAGE 2 (20 min): Sleep spindles. Memory consolidation begins. Body temperature drops. NREM STAGE 3 — DEEP SLEEP (20-40 min): Delta waves. Hardest to wake. Physical restoration. Growth hormone release. Most deep sleep occurs in the FIRST HALF of the night. REM SLEEP (10-60 min): Brain active, body paralysed. Dreaming. Emotional regulation, creativity, memory integration. Most REM occurs in the SECOND HALF of the night. IMPLICATION: An alarm that wakes you 6 hours in cuts your REM sleep. Two glasses of wine before bed reduces REM by 20-24%. Both actions have measurable cognitive costs the next day.

ALCOHOL: Widely misunderstood. Alcohol is sedating but it's not sleep. It fragments sleep, suppresses REM, and causes early-morning waking as it metabolises. Even 1-2 drinks measurably degrades sleep quality. CAFFEINE: Has a half-life of 5-7 hours. A 3pm coffee still has 50% caffeine in your system at 10pm. Caffeine doesn't eliminate sleep drive — it masks it. The sleep pressure keeps building, but you can't feel it. BLUE LIGHT: Suppresses melatonin for up to 3 hours. Screens at 10pm shift your sleep clock to 1am. TEMPERATURE: The most underrated sleep lever. Your bedroom at 22°C (72°F) vs 18°C (65°F) can reduce deep sleep by 20%. The optimal sleep temperature for most people is 18-19°C.