Sleep isn't one thing — it's four stages cycled every 90 minutes. Cut it short and you lose the good stuff first.
Each sleep cycle is roughly 90 minutes and contains light sleep, deep sleep and REM sleep. Deep sleep does most of the physical recovery. REM is where memory and mood consolidate.
REM concentrates in the second half of the night — so cutting sleep from 7–8 hours to 5–6 hours doesn't just lose 25% of sleep, it loses ~60% of your REM. That's why short-sleepers often feel emotionally 'off'.
Simple wins: fix a wake-up time (matters more than bedtime), 30 minutes of morning sunlight, no caffeine after 2 pm, and a slightly cool bedroom (18–22°C).
This article is educational and general. Your situation has its own context — for symptoms that are severe, sudden, persistent or worrying, consult a qualified medical practitioner.
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