[Free content] 💫 8 Hours of Sleep: The Big Lie

What if the 8-hour sleep rule is a myth? 💫 In this article, I debunk that belief using history, neuroscience, and longevity science.

For decades, we've been told that "8 hours of sleep per night" is the gold standard for good health. But... is it really true? And where does this fixed idea come from?

If you're a biohacker, you already know: one-size-fits-all rules don’t work for everyone.

In this article, I break down the myth, explore the history of sleep, its different phases, why some people thrive on less, and — most importantly — why deep sleep is in free fall, to the detriment of our longevity and brain health (hello, neurodegenerative diseases).

🔬 Disturbed Sleep: The Serious Consequences You May Be Ignoring

Did you know? Chronic sleep deprivation or frequent interruptions (night shifts, healthcare workers, police, firefighters, on-call doctors, etc.) have dramatic health consequences. Expect another article soon on that subject.

🌙 What Is Sleep?

Sleep isn’t a passive state. It’s an active process, during which your brain and body perform vital tasks: repair, memory consolidation, brain detoxification, hormone regeneration, and more.

The Stages of Sleep

There are 2 main types of sleep:

• Non-REM sleep (light and deep)

• REM sleep (Rapid Eye Movement)

A full sleep cycle lasts 90 to 110 minutes and repeats several times per night:

• Light sleep (Stage 1 & 2): transition to sleep, heart rate and body temp drop

• Deep sleep (Stage 3): cellular repair, growth hormone release, brain cleaning via the glymphatic system

• REM sleep: vivid dreams, emotional memory processing, brain activation

Key study: Deep sleep is essential for cognitive longevity. Its decline is linked to faster brain aging (PMID: 30814454)

📜 A Short History of Sleep

The "8 hours of sleep" concept is relatively modern.

Before the industrial era…

Before electricity, humans practiced biphasic sleep:

• First phase: from nightfall to around midnight

• Night awakening: to meditate, pray, write, or chat

• Second phase: until dawn

This model was documented in medieval texts, monastic journals, and among isolated tribes — more in sync with natural circadian rhythms.

It was artificial lighting and industrial work schedules in the 19th century that imposed a single 8-hour block of sleep — ideal for productivity, not biology.

🤜 Why Some People Don’t Need 8 Hours

The “Sleepless Elite”

Some people have genetic mutations (like on the DEC2 gene) that allow them to function perfectly with just 4–6 hours of sleep and no cognitive decline.

Study: DEC2 mutation identified in functional short sleepers (PMID: 19679818)

But caution: that’s a rare exception. Most people who sleep very little are actually missing deep or REM sleep — even if the total duration looks decent.

📉 The Fall of Deep Sleep: A Silent Danger

Since the 1960s, deep sleep has been decreasing in the general population, especially after age 40.

Why?

• Blue light exposure at night

• Chronic stress and high cortisol

• Poor diet

• Lack of physical activity

• Noise pollution

Less deep sleep = less hormonal regeneration, more inflammation, weaker brain plasticity

What science says:

• Deep sleep starts to decline in your 30s, especially with poor lifestyle habits

• Chronic deep sleep loss is linked to increased dementia and mortality risk (PMID: 34657062)

🧬 Why Deep Sleep Is Non-Negotiable

Unlike REM sleep, deep sleep is essential:

• Your body produces growth hormone during this stage

• It activates the glymphatic system, cleaning out beta-amyloid plaques linked to Alzheimer’s

• It regulates inflammatory cytokines

• It consolidates declarative memory

And no — it’s not just about total sleep time. You can sleep 9 hours and only get 40 minutes of deep sleep if your habits are poor.

🔎 What’s the Optimal Amount of Deep Sleep?

It depends on age and lifestyle, but on average:

🔹 Healthy adults (18–65 years):

• Aim for 1.5 to 2 hours of deep sleep per night (20–25% of total sleep)

• I personally sleep only 6h30 most nights (maybe 7h three times a year!)

• But my deep sleep is consistently 1h23 — oddly precise, but it’s my sweet spot

• With less, my emotions and energy drop sharply

👶 Children & teens:

• Can get 3–4 hours of deep sleep, due to rapid growth and brain development

👵 After 65:

• Deep sleep naturally declines, sometimes to just 30 minutes per night

• This is linked to less growth hormone, slower recovery, and cognitive decline

• BUT: it can be optimized with targeted strategies (coming in a future article!)

⚠️ If Your Deep Sleep Is Under 60 Minutes:

It could be due to:

• Excess stress or high cortisol

• Late-night screen time or blue light

• Deficiencies in magnesium, glycine, or zinc

• Lack of movement or sunlight

• Sleep disorders (micro-awakenings, apnea)

🧰 If You’re a Biohacker…

Use tools like Oura Ring, Whoop, or Dreem to track your deep sleep precisely. I never sleep without my Oura!

Your goal: at least 90 minutes of deep sleep per night to support:

• Growth hormone & testosterone production

• Brain detox via the glymphatic system

• Memory consolidation

• Cellular longevity

📌 So… Are 8 Hours a Myth?

👉 They’re a useful guideline, but not a biological law.

Some people thrive on 6.5 hours (like me). Others may need 9 depending on age, stress, or constitution. But 10+ is usually too much!

What matters most: deep and REM sleep quality — not just total time.

⏳ What’s Next?

In a future article, I’ll dive into real strategies to improve your deep sleep: from nutrition to advanced biohacks (red light, peptides, glycine, targeted supplementation…)

But for now, remember:

• ⛔ 8 hours is not an absolute truth

• ✅ Deep sleep is your #1 priority

• 🕯️ And looking to the past might help you realign with your biology

Valérie Orsoni
Founder – ValBiohacker.com | Longevity Explorer | Biohacker since 1998
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