😴 Throw out your Casper mattress. Really.

Rosa Hamalainen
😴 Throw out your Casper mattress. Really.

I’ve been obsessed by a question lately.

What if we could sleep the same amount of time, but be MUCH more rested? What if we could dial up our sleep “effectiveness”?


Let me tell you how I got here.👇

I slept 10+ hours each night last weekend. And felt exhausted.😭


Not just “need a few more hours” tired. But completely, overwhelmingly, “I SHOULD FEEL GREAT BUT I DON’T”, exhausted.

Here’s what that looks like from my Nokia sleep tracker:


This is what inefficient sleep looks like.
10+ hours in bed. Barely any deep sleep, especially in 1st half of the night, with multiple interruptions.

In fact, I’ve spent 2 weekends with 10+ hours each night and 7+ hours on the weekdays. And I’m continually waking up exhausted and crashing in the afternoon.

I haven’t felt rested in months. And I’ve been getting the same amount of sleep as I always have (if not more). So…what’s going on?!

You’re probably aware that we go through different sleep stages through the night, with REM being the most well known and researched. But there’s a stage before REM called N3.

If we’re not getting enough N3 sleep, we will wake up feeling completely exhausted even if we’re getting our 8 hours.

We need deep N3 sleep to feel refreshed when you wake up in the morning. Period. So while I’m sleeping 10+ hours, I have a hunch my deep N3 sleep is basically trash.🗑

What is N3 sleep? Here’s what you need to know:

1. N3 goes by many names.🎷

N3 sleep = deep sleep = slow-wave sleep = Delta sleep.

It’s (surprisingly) a technical term with a clear definition and measurement (presence of delta waves).

2. It’s when your body actually repairs and grows.🌱

Nothing short of magic — during N3 your body goes through cellular rebuilding and repair — builds bone and muscle, repairs and regenerates tissues, creating and storing memories, processing learnings from the day, and more. While REM is more emotional processing, deep sleep is critical for truly recovering and repairing the body including detoxifying the brain. It’s crucial for both hormonal regulation and physical renewal. In short, we need this. There’s no such thing as too much deep sleep.

3. The bulk of it happens in the earlier hours of your sleep.⏰

You have more N3 sleep in the first half of the night than the second half. REM is the opposite — getting longer as you proceed through the night.


4. Temperature is a key factor.❄️

Have you heard sleeping in a cold room can help you sleep deeper? In N3 sleep, your body drops to the lowest temperature during the night — so providing an environment for your body to get and stay cool is key. [NIH, 2012]

5. Without sufficient N3, you’re not going to be healthy.💪

Short term, your body is not physically repairing or mentally processing the day and you’re not going to feel rested at all. Long term is even worse. Alzheimer’s, diabetes, heart disease, stroke…the connections between lack of N3 sleep and chronic illness goes on and on.

All in all, N3 sleep is the holy grail.💰 (In my humble opinion)

It’s where we repair, build, and learn. It staves off many chronic illnesses. It seems to make sense that I’m missing N3 sleep with all the weird health stuff I’ve been experiencing the last few months.

I’ve become obsessed with understanding and experimenting with my own N3 sleep. So what affects N3 sleep? How can we hack it? How do we know if we’re not getting enough?

Here’s where it gets unfortunately tricky.

We know N3 sleep is critical — but we know surprisingly little beyond that.

Sleep research has been notoriously difficult historically (getting people in a lab, connecting electrodes to their head, trying to mimic a normal sleep environment, etc etc). This is changing with higher quality wearables like the Oura and Motiv rings, which I’m super stoked about.

But for now, we’re left to experiment on our own.

And (as I’ve learned from some of our most courageous patients) sometime’s that’s what it takes — being that pioneer in your health journey. Taking your health in your own hands when there are no clear answers and no clear path.

So let me be SUPER clear, everything beyond this sentence is my own personal experience and detective work — though rooted in as much science as I could find, of course.

After hours of endless googling, reading, and talking to experts — here’s what I discovered. Hopefully this can help you. :)

How do I know I’m not getting N3 sleep?
Here’s the signs that my exhaustion problem might be a “needs more N3” instead of “needs more time in bed”.😴

😴Not Feeling Rested: I don’t feel rested when I wake up, no matter how many hours I sleep.

🌵Stiffness: My body is sore in the mornings — as if I had lifted heavy weights the day before.

🔥Temperature: I don’t have AC and it’s been extremely hot at night. I often wake up drenched in sweat.

⏯Interruptions: I’m waking up multiple times a night, especially in the first half, when I should be falling into deep N3 sleep. I’m much more sensitive to light & sound than I was a few months ago- which makes me think I’m spending more time in light sleep stages.

🧠 Cognition: I’m having trouble processing thoughts or remembering even what I ate for lunch yesterday. Yes, it’s that bad.

⌚️️ Tracking: My sleep tracking watch shows my getting very little deep sleep. It’s tracking movement, and isn’t super accurate, but I’ve noticed how I feel correlates pretty accurately with the amount of “deep sleep” recorded. At the very least, it’s tracking me moving quite a bit through the night — which shouldn’t be happening during N3 sleep.

Moments like last Saturday morning — I wake up feeling like I’ve failed myself. I “wasted” 10+ hours “not doing anything”. 10+ hours sleeping and not rested from it. Increasing hours isn’t doing anything. Anyone else with me?

Something needs to change. So here’s what I’m doing.

👇Here’s my plan for increasing N3 sleep.

👻 Throwing out my Casper Mattress: Foam mattresses are easy to ship, but horrible for thermoregulation. I switched back to my old spring mattress and my night sweats stopped.

🔥Heating Up 1+ Hour Before Bed: It’s counterintuitive but a hot shower (or sauna) 1–4 hours before bed helps our bodies cool — the steep decline from hot to cold signals it’s time for bed. I used to do this right before bed, but now am switching to an earlier shower to let my body cool effectively. [NIH, 2019]

❄️️Cooling During Sleep: Keeping the room cooler or using a tool like the ChiliPad to help keep your body cool and staying in N3 sleep. [NIH, 2019]

🙊Intermittent Fasting: Time restricted eating — eating less before bed assists N3 sleep. I’m stopping eating 3 hours before bed. [American Sleep Association]

🦍Paleo Diet: Lower carb diets with healthy fats has also been correlated with deeper N3 sleep. Goodbye sugar (for a little bit!). [American Sleep Association]

If I had to guess, I’d say stress and anxiety also play a huge role in keeping us from falling into that deep sleep. Also, light, sound, temperature, our internal clock, etc etc. And we haven’t even talked about circadian rhythm, melatonin, supplements…So, all the things,😂 but let’s start here and see what happens.

It seems to me that, while we may be sleeping the same times, our quality of sleep has gone down, which is primarily due to our inability to fall into deep, restful, regenerative N3 sleep. Which is one reason we’re all feeling exhausted.

What would happen if we could effectively improve our N3 sleep — so we could sleep the same length but be much more rested, sharper, and healthier?🤔

I’m into that.👏

I’ll keep you posted on what happens. :)

In the meantime, I’d love to hear your thoughts, tips, and feedback. (on sleep and this email in general!) Just hit reply & it’ll come straight to me.



💩 P.S. Struggling with digestive issues?

Or know someone who is? (IBS, IBD, Leaky Gut, SIBO, undiagnosed symptoms, etc.) We’re launching a functional medicine pilot program for patients with these conditions, and we’re covering 70% of the cost for our initial batch.You’ll get to work 1:1 with a functional medicine doctor, get 24/7 access to a care team, and more. Just respond to this email if this sounds like something that could help you — it’ll come straight to me (Tara)! Open to patients in CO, WA, CA (waitlist only in CA, we’re sold out!)

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Rosa Hamalainen
Product & Operations at Rupa Health. Stanford University.
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