Inquisitive.me

Is 4 Hours of Sleep Really Enough?

I’ve been pondering this question for a while—and it comes up a lot in my practice, too. We all know sleep is important. But how important is it really? And is it actually possible to function on just four hours of sleep, like some people claim?

Let’s find out.

What’s the Deal with Sleep, Anyway? 🤔

Let’s start with the basics. While we sleep, our body cycles through two key stages:

1. REM sleep (Rapid Eye Movement – aka dream sleep)
2. Non-REM sleep (dreamless sleep)

Each full sleep cycle lasts about 90 minutes and repeats 4 to 6 times per night—if you’re clocking that golden eight hours. During REM sleep, your eyes dart around beneath closed lids, and your brain activity ramps up. In contrast, Non-REM sleep is deeper and divided into three stages, each with its own purpose:

💤 Stage 1: Sleep Onset (N1)

• Duration: 1–5 minutes
• Makes up ~5% of total sleep
  Your breathing slows, and you hover between wakefulness and sleep. It’s easy to wake you at this stage—your brain hasn’t quite signed off yet.

😌 Stage 2: Light Sleep (N2)

• Duration: Starts around 25 minutes in the first cycle and gets longer as the night goes on
• Makes up ~45% of total sleep
  Heart rate and body temperature drop. If you grind your teeth, this is when it tends to happen. Most importantly, this stage is a powerhouse for neuroplasticity—your brain’s ability to reorganize and form new connections.

That’s when two key types of memory are being shaped:

• Declarative memory (facts, events—you can consciously recall and talk about it)
• Procedural memory (skills and habits—you do it, even if you can’t explain how)
  🧠 Think of it like this: ever tried to teach a new driver how to start on a hill without stalling? You might know how to do it, but explaining it? That’s a whole different story. That’s procedural memory in action.

🦥 Stage 3: Deep Sleep (N3 or SWS)

• Makes up ~25% of total sleep
  This is where the real magic happens. Your brain emits slow, high-amplitude waves. Waking up from this stage feels like being dragged out of a cave—you’re groggy, disoriented, and would love nothing more than to roll back into bed. That’s sleep inertia.

But don’t underestimate it:

Deep sleep is essential for:

• Tissue repair and regeneration
• Muscle and bone growth
• Immune system support

As we age, we get less of this stage and more of N2 instead. That’s part of why older adults often don’t feel as refreshed after a night’s sleep.

So, Is 4 Hours Enough?

Not really.

You might survive on four hours, but you won’t thrive. Skimping on sleep cuts short your REM and deep sleep—the two stages that restore your brain and body. Without them, your memory, focus, emotional regulation, physical recovery, and pain tolerance all take a hit.

A well-rested brain equals a well-rested you—and that makes it way easier to soak up new information, develop lasting habits, and master coordination skills. Whether you’re studying, learning something new, or trying to build better routines, proper sleep is the foundation it all stands on.

Running on too little sleep is like trying to train for a marathon while running on fumes. Possible? Maybe. Sustainable? Definitely not.

4 hours of sleep? Sure, if you want to feel like a zombie! 🧟‍♀️

We spend about one-third of our lives asleep, so it’s worth understanding what sleep actually does for us—and what happens when we don’t get enough of it.

First off: sleep is not a passive state. Our brain doesn’t just switch off while we snooze—it gets to work. Think of it as a night shift for restoration and reset.

Sleep is still a bit of a mystery in research, but we know it plays a huge role in regeneration and learning. During the night, new synaptic connections are formed while unimportant ones get trimmed down—a bit like pruning a tree to help it grow. This keeps our brain from becoming overwhelmed with unnecessary clutter (Patel et al., 2023).

Dr. Lars Dittrich, a German sleep expert, puts it simply: during sleep, your brain is “like cleaning, oiling, and tightening the gears.” Basically, sleep is maintenance time—like the street cleaners tidying up the city overnight.

And speaking of cleanup: we have a built-in waste disposal system in the brain called the glymphatic system. It works independently from our blood and lymph systems, flushing out metabolic waste that builds up throughout the day. Think of it as the brain’s janitorial crew, sweeping up the mess so things stay sharp and functional.

If this waste isn’t cleared out properly, it can interfere with how our brain works. Since most of that cleaning happens during sleep, skimping on it can lead to some nasty side effects—like poor memory, reduced focus, irritability, and even a higher risk of chronic disease.

We live in a world that glorifies late nights and early mornings—as if running on empty is something to be proud of.

But let’s face it: trading sleep for hustle is a bad deal.

What’s the impact of missing out on sleep? 😩

Even mild sleep deprivation can make your brain feel like it’s running on empty. Thinking becomes harder, memory takes a hit, and reaction times slow down—something you can actually test with the Psychomotor Vigilance Task. It also messes with your mood and, in extreme cases, can lead to hallucinations (Patel et al., 2023). Anyone who’s ever pulled an all-nighter knows the feeling: it’s like being drunk without the fun part. In fact, a study by Williamson & Feyer (2000) confirmed that moderate sleep deprivation produces impairments similar to alcohol intoxication.

If you want to see just how wild sleep deprivation can get (without putting your own sanity on the line), check out German YouTuber Techtastisch or the English version by Ethan Fleming, both of whom stayed awake for 100 hours. Techtastisch’s video is super entertaining (though German skills help), while Ethan’s version is especially eye-opening—he shares how the challenge triggered a complete personality shift and left him deeply depressed.

Let’s move beyond the short-term effects and talk long-term. Chronically missing out on sleep messes with your whole body. It can cause blood pressure and blood sugar levels to remain elevated, increasing the risk of obesity, diabetes, and cardiovascular disease (Grandner et al., 2016; Nagai et al., 2010). On a hormonal level, it disrupts sleep homeostasis and activates the hypothalamus-pituitary-adrenal (HPA) axis, leading to increased cortisol—the infamous stress hormone (Nollet et al., 2020). Translation: your immune system takes a hit. On the flip side, consistent, quality sleep boosts your resilience to daily stress and helps regulate your mood (Blaxton et al., 2017).

While a single bad night may just leave you groggy, long-term sleep deprivation can impair your ability to learn, recall, and make sound decisions (Alhola & Polo-Kantola, 2007; Bishir et al., 2020). It also increases the risk of depression—and depression itself often feeds right back into poor sleep, creating a vicious cycle (Roberts & Duong, 2014). Ethan Fleming’s experiment is a chilling real-life example of how this loop can take hold.

Chronic sleep deprivation has even been linked to a Alzheimer’s disease, as well as worsening other neurological disorders like Parkinson’s disease, multiple sclerosis, and Huntington’s chorea (Bishir et al., 2020; Wu et al., 2019).

Still think you don’t need more sleep? It might just be your brain playing tricks on you. For the first few days of sleep restriction, you’ll definitely feel worse. But then something strange happens—your body hits a plateau. You stop feeling quite so tired and start to believe, “Maybe this is fine.” But it’s not. Your brain hasn’t fixed anything—it’s just adapted to survival mode.

That doesn’t mean you suddenly need less sleep. It just means your brain has reluctantly accepted its new baseline. And let’s be honest: after everything we’ve covered, surviving isn’t the same as thriving.

---

📝 Key takeaways

• Sleep cycles last around 90 minutes and alternate between two main types: Non-REM (includes deep sleep) and REM (dream sleep).
• Non-REM sleep is made up of three stages—Sleep Onset (N1), Light Sleep (N2), and Deep Sleep (N3)—each with specific restorative functions.
• While we sleep, the brain carries out vital tasks: consolidating memories, reorganizing synapses, and clearing out waste via the glymphatic system.
• Lack of sleep impairs thinking, reaction time, and memory—on par with being legally intoxicated.
• Chronic sleep deprivation raises the risk of serious conditions like obesity, diabetes, heart disease, and neurodegenerative disorders.
• The “I only need 4 hours of sleep” myth is just that—a myth. Your body might adapt, but the damage still adds up.
• Consistent, quality sleep boosts your immune system, improves your mood, and makes you more resilient to daily stress.

---

I’m truly passionate about this topic because I regularly see the effects of poor sleep in my practice—especially in patients dealing with pain or recovering from injuries, when quality sleep is essential for healing. And I’ve experienced my own fair share of sleep issues too.

Back in my gaming days, all the way through my mid-20s, my sleep routine was completely out of whack. I’d often stay up until 2 a.m., sometimes even 4, and sleep until 9, noon, or later. On top of that, I was working in hospitality to fund my studies, and my schedule—especially on weekends—was all over the place.

Looking back, it’s no surprise my mood was terrible. I was constantly tired, quick to snap, and mentally drained. My habits were chaotic, I lacked energy and focus, and I barely scraped through my studies. Gaming became my escape from adult responsibilities I just wasn’t ready to face.

Today, things are different. My sleep routine is steady, and it’s rare for me to have trouble falling—or staying—asleep. I can feel the difference every day.

Recovering my sleep routine was a game-changer. For a deeper dive into what really helps, I’ve shared more in that post.

---

Thanks for spending this time with me. Keep exploring, stay open to new ideas, and remember—growth is a journey, not a destination.

Take care,

Carina 🦊