So, how did you sleep last night?

Seriously.

We ask each other this all the time, then move on before the answer lands.

Because for most people in this community, the honest answer is: not as well as you could be. Not dramatically. Just a steady, low-grade erosion that's become so normal you've stopped noticing it. The slightly slower reactions. The shorter fuse. The way whole conversations happen while your mind is somewhere else. Most of us have normalized that version so thoroughly that we've forgotten the other one exists.

I'm writing this a few weeks into new fatherhood, averaging 6.5-7 hours of broken sleep. Research suggests most new parents are around five and a half at this stage, so I have no right to complain. But I notice the difference anyway. Not in quantity, in quality.

Sleep is the most leveraged physical input most of us chronically undervalue. Not because the information isn't out there. We've all read the articles. We know. We still struggle with it.

The problem is a category error. We treat sleep as a cost: something we give up to get more done. The evidence says it's a return. You don't cash in sleep for productivity. You cash in productivity when you skip it.

Deep sleep is when physical repair happens, growth hormone is released, and memories are consolidated. REM is when the brain processes emotion and recalibrates its threat response. Skip those stages, and you're not just tired. You're running on a system that hasn't been serviced.

Stanford researchers who had basketball players extend sleep to ten hours saw shooting accuracy improve by 9% and sprint times drop. From one intervention: sleep.

A study by Cambridge and Fudan University of nearly 500,000 adults found that seven hours is optimal for cognitive performance and mental health; both shorter and longer durations were associated with worse outcomes.

Sleeping under seven hours consistently is associated with a 14-34% increase in all-cause mortality risk. Seven hours is the population optimum. But almost no one leading a demanding life is actually getting their requirements met.

Consistency matters as much as duration. Same bedtime, same wake time, even on weekends. Your circadian rhythm is a biological system that responds to regularity. Most people obsess over hours and ignore the schedule. It might matter more.

I've been tracking sleep with an Oura Ring since 2019, when my brother introduced me to it. Six years of data.

My best sleep on record coincides almost exactly with Toronto's lockdown period. HRV in the high 50s. Deep sleep for over two hours a night. I was ordered to stay home, my commute disappeared, my schedule compressed, and my sleep became the best it had ever been. I didn't engineer it. The circumstances did.

Then restrictions lifted, and life returned. HRV down from the high 50s to 40ms. Deep sleep decreased from 2h 10m to 1h 19m. The sleep score looks nearly unchanged. Which is why the headline number is the wrong thing to track.

The newborn is a recent factor, but not the whole story. The data was already drifting before he arrived. He just made the gradient visible faster.

Sleep regularity is holding at Good, trending toward Optimal. Even with a newborn running the night schedule, consistent wake time is doing its job. I'm not optimizing a system under construction. I'm protecting what's there.

Most of the levers for better sleep require doing less rather than more, which runs against how high performers think about optimization.

Caffeine timing is the most underestimated. Caffeine's half-life is around five to six hours. A 2 pm coffee is still working at 8 pm. Most people are quietly wiring themselves for lighter sleep every night without realizing it.

Alcohol is the most underestimated disruptor. It sedates you but fragments the second half of the night and suppresses REM. You wake up feeling like you slept. You didn't.

Stress and cortisol are the most overlooked lever of all. What degrades sleep quality most isn't caffeine or bedroom temperature. It's a nervous system that never fully exits threat mode. If you're reading this on your phone while half-thinking about something else, that's not a coincidence. That's the operating mode that follows you to bed. Elevated cortisol keeps you in lighter sleep stages and suppresses deep sleep. This is why exercise matters: it's one of the most reliable ways to metabolize cortisol and trigger the parasympathetic response that enables deep sleep. Resistance training and zone 2 cardio directly improve sleep architecture and move HRV over time. And it's why wind-down isn't optional. Thirty to sixty minutes before bed, without work, without screens, without anything keeping cortisol elevated. Not because it's relaxing. Because your nervous system needs a hard stop, not a fade out.

Light is simple, and almost nobody does it consistently. Ten minutes of outdoor light in the morning sets your circadian clock. Dim the lights an hour before bed. Your brain is literal about this signal.

Environment is a one-time fix with compounding returns. Cool (65-68°F), dark, quiet. If your partner's snoring is the variable, that's worth solving directly: earplugs, white noise, or the harder conversation.

Caffeine cut at 1 pm. When the baby goes down, I go down. Consistent wake time regardless of how the night went. None of this is heroic. It's the minimum that keeps the floor from dropping further.

A few things I've found meaningful once the schedule is in place: the Oura Ring, not because the data is perfect, but because it changes behavior. Eight Sleep if temperature is an issue, especially for couples who run hot and cold. Magnesium glycinate in the evening has made a real difference in sleep onset (I use Moonbrew, perhaps childish), and I avoid melatonin. Blackout curtains or a sleep mask. White noise if you're in a city. None of these fixes a bad schedule. But once the schedule is there, they compound it.

None of which means the goal is to become Bryan Johnson and engineer a perfect score at the expense of everything else. My lockdown peak was real, but it was a product of circumstances I wouldn't choose to recreate. The years since have included career changes, a new venture, travel, weddings, a pregnancy, a few moves, and a beautiful baby boy.

The sleep gets harder to protect sometimes. That's not failure. That's a life.

The goal is simpler: raise the floor. Better sleep doesn't give you a perfect life. It gives you more access to the one you have. The decision you make cleanly instead of second-guessing it. The patience instead of a short fuse. The conversation you're actually in instead of being half-present. The morning you wake up and feel like going after something hard rather than just clearing the queue.

I'm building a series called The Stack: nine issues on the physical foundations that compound over time. Sleep is this one. Each layer connects to the next.

A few questions worth hitting reply on:

I read every reply.

If you missed the previous issue or want to read ahead, it's worth going back.

01 — Sleep: The Floor You Keep Lowering (you're here)
02 — Blood Sugar: The Interior Condition

See you next Sunday, Eric

P.S. Next week: blood sugar. Not a diabetes topic — an energy topic, a mood topic, a decision-quality topic. Poor sleep directly impairs glucose regulation, so these two are more closely linked than most people realize. Read it here if you want to get ahead.