# Learn

Short, practical guides distilled from the episode and the literature. Every claim links to the study behind it.



- [Beware of health anxiety](anxiety) — Over-fixation on sleep scores can hurt more than it helps.

- [Resilience beats optimisation](resilience) — The endgame is performing well after a bad night — not a perfect sleep score.

- [How you feel is the primary metric](subjective) — "You felt worse" is the only directional signal you need.

- [Run one-variable self-experiments](experiments) — Trackers tell you how you slept, not why. Finding the why is your quest.

- [Sleep apnea: the hidden epidemic](apnea) — 70–80% undiagnosed. 90–95% among women. ~1 billion people.

- [Insomnia, RLS and circadian disorders](otherdisorders) — Apnea is only one variant. Free validated questionnaires exist for the rest.

- [From 'how do you feel' to a sleep study](ladder) — Subjective → free questionnaire → wearable ($100–600) → sleep hospital.

- [What to trust on your wearable](wearables) — Total sleep time: yes. Deep/REM and 'sleep scores': no.

- [Resting heart rate: the canary in the coal mine](rhr) — In 1,200 nights of one client's data, every 1 bpm drop in RHR = ~6 more minutes of sleep.

- [Light: the world is physically brighter](light) — Skyglow, screens and 24-hour business — but morning light offsets evening light.

- [Sound: aim for ~35 dB, and hate inconsistency](sound) — Urban bedrooms sit at 60–70 dB. It's the *change* in sound that wakes you.

- [Temperature and air](temperature) — 64–68 °F (18–20 °C). Don't crank the AC into a noisy on/off cycle.

- [Other beings: the sleep divorce](partner) — People sleep worse sharing a bed. Separate sheets are the realistic fix.

- [New places: the first-night effect](travel) — Recreate home — sound, light, feel, temperature, smell.

- [Caffeine: timing is the lever](caffeine) — Rested + caffeinated > deprived + caffeinated. A coffee needs ~8–9 h before bed.

- [Alcohol: sedative first, saboteur second](alcohol) — Falls you asleep faster, then fragments the second half of the night and suppresses REM.

- [Screens: it's the arousal, not the blue light](screens) — The search for novelty is what disrupts sleep. Boring content is fine.

- [Sleep and fat loss](fatloss) — Same diet, 5.5 h vs 8.5 h sleep: 55% less fat lost. Sleep is a fat-loss tool.

- [Cook or baker? Measure first, then use concepts](cookbaker) — Two weeks of weighing everything, then 1–3 airtight rules.

- [Meal timing and sleep](mealtiming) — Big late meals hurt sleep efficiency; finish ≥ 3 h before bed.

- [Evidence tiers for sleep aids](tiers) — Level 1: magnesium, chamomile/apigenin, melatonin. Level 2–3: kiwis, tart cherry, omega-3.

- [Melatonin done right](melatonin) — 0.3–0.5 mg, ~1 h before bed, only to reset circadian rhythm. Never at 2 am.

- [Energy: the #1 complaint](energy) — Hidden vs visible stressors. Exercise gives energy; under-fuelling and stimulant loops take it.

- [The 5-4-3-2-1 fat-loss rule](54321) — 5 days active · 4 structured sessions · 3 sweaty · 2 strength · 1 very-high heart rate.

- [Exercise timing and sleep](exercise) — Evening training is fine — unless it's vigorous and ends within an hour of bed.

- [Naps and the afternoon dip](naps) — The dip is normal. Short early naps help; long late naps steal from the night.

- [Regularity beats duration](regularity) — In 60,000 people, sleep regularity predicted mortality better than sleep length.

- [How much sleep, really?](howmuch) — ≥7 h for adults per the AASM/SRS consensus; 7–9 h is the range. Less with age is normal.

- [Children and postpartum sleep](postpartum) — One of the largest causes of sleep disorders in women — and it can persist for years.

- [Aging and sleep](aging) — You'll sleep a little less as you age — resist the rest.

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Educational summary of published research, not medical advice. Screening scores are not diagnoses. If a score is elevated or you feel unwell, talk to a clinician.

SleepShred for iPhone: https://apps.apple.com/app/id6802040541