Hi! Welcome. You being here means more than you know. Knowing it lands with someone like you keeps me going. I'm Lavena Xu-Johnson. I write about psychology for founders. Why? Because scaling a business means scaling ourselves first.
Happy Wednesday, founders,
A really good friend was in town last week. He is an investor, writer, and community builder who is constantly on planes, at events, and working across time zones. We hadn’t seen each other for a year, and as soon as I sat down, he noticed the small noise-blocking earplugs in my ears.
Knowing how disciplined and high-functioning he is, I had a feeling he’d be happy letting me brainwash, I mean, share with him some of the “bio-hacking” experiments I’ve been running on myself so he could test them too.
Beyond nootropics, brain and gut supplements, which I wrote about a few weeks ago here, I shared how I preserve my energy and cognitive performance by managing three environmental factors: noise, CO₂, and blue light.
Noise was the one that hit me hardest. After COVID and giving birth, I noticed a significant shift in how I felt in malls, airports, and conferences. Within less than two hours, I’d develop a bad headache, my ‘snow’ vision would worsen, I’d start yawning from fatigue, feel impatient and irritable, and I wanted to escape to a dark, quiet space. Only after a few more occurrences, I realized - this is classic sensory overload from overstimulation.
One of the unexpected gifts of getting older is becoming more observant and attuned to my body. I didn’t want sensory overload to run my day, so I started looking for ways to reduce it and protect my energy. That’s when I discovered noise-blocking earplugs. Once I began wearing them in crowded places, the headaches vanished. My partner says I look like a different person in crowded spaces now - calmer, more present, less scattered.
Besides earplugs, I wear blue-light-blocking glasses when using screens and keep a CO₂ monitor in different rooms, all small ways of protecting my cognitive resources.
We usually go about our days without thinking about how indoor CO₂, blue light at midnight, and chronic noise affect us. Yet, the research suggests these three variables do impact our decision-making, creativity, logic, and strategic thinking.
So this week, I’m continuing our series on cognitive performance optimisation through the lens of neuroscience.
Let’s dive in.
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Air: the CO₂ fog that makes you slower
Most of us think “air quality” is a long-term health thing. The data says: it affects your prefrontal cortex immediately.
A 2023 meta-analysis combined 15 studies on short-term exposure to indoor CO₂ and cognitive performance, focusing on elevated CO₂ levels from fresh air (<1000 ppm) into the 1000–1500 ppm and 1500–3000 ppm ranges. Performance on complex cognitive tasks dropped significantly, while performance on simple tasks was much less affected.
The same paper suggests two patterns that are very relevant to how we work:
The more complex the task, the more CO₂ decreases decision-making, strategy, and creative problem-solving.
The longer you sit in it, the worse it gets. Beyond ~120 minutes at high indoor CO₂, complex task performance deteriorates further.
Earlier work from Berkeley Lab tracked how rising CO₂ levels affect office-style performance across activity, orientation, initiative, utilisation, and strategy. Once CO₂ hit 2,500 ppm, the most significant declines were in strategy and initiative - exactly the functions founders rely on most.
Strategic thinking and taking initiative showed the most dramatic declines in performance at 2,500 ppm carbon dioxide concentrations. “Is CO2 an Indoor Pollutant? Direct Effects of Low-to-Moderate CO2 Concentrations on Human Decision-Making Performance”
How to avoid feeling ‘drunk’ from high indoor CO₂ levels
Steven Bartlett once mentioned on The Tonight Show that he keeps a CO₂ monitor in his podcast studio to make sure levels don’t creep above 1,000 ppm. Before he knew about this, he said, he probably recorded the first 200 episodes with guests effectively in “drunk” mode.
The good news is, it’s not rocket science. There are a few simple, practical steps you can take to avoid the classic scenario of everyone yawning halfway through a “strategic” meeting:
Get a cheap CO₂ monitor on Amazon: you can start to pair task type with air quality - put low-stakes tasks in the “stale” parts of the day/space, move deep thinking to earlier in the day or fresher rooms.
Limit time spent in stale-air meeting rooms: If you’re stuck in a high-CO₂ meeting room, limit high-stakes decisions to <90 minutes, and build in “vent breaks”.
Make sure your bedroom can breathe: according to research, poor ventilation in closed bedrooms with high CO₂ concentration leads to poor sleep quality and decreased logical thinking the next day.
When choosing/designing your office: ventilation should be considered as a cognitive performance budget.
Light: blue light, sleep, and your circadian brain
We all know someone who wears those orange glasses; if you ever ask, you’ll know it’s not a fashion statement but blue-light-blocking lenses. These days, they’re not just orange; they come in clear glasses too.
Personalised light interventions using blue-blocking glasses at night and blue-enriched light during work helped us sleep better, maintain performance, and realign our circadian rhythm more quickly after schedule changes - perfect for frequent flyers.
Our brain doesn’t just run on caffeine and willpower. It runs on a 24-hour light–dark rhythm that sets our attention span, mood, and ‘error rate’. At the centre of this is a set of retinal cells that are especially sensitive to blue light (around 400–500 nm). They send a direct “daytime” signal to your master body clock, the suprachiasmatic nucleus.
The problem is not blue light per se; it’s exposure to blue light too close to bedtime. Reviews of evening blue light from devices show a consistent pattern: late exposure delays melatonin secretion, delays sleep onset by three hours, shortens total sleep, and reduces sleep efficiency. Over time, this circadian disruption is linked to mood disturbances, cognitive decline, and metabolic problems.
Even low levels of ambient light during sleep - streetlights, standby LEDs, or “just a small lamp”- are associated with poorer sleep quality, more daytime fatigue, and higher risk of mood and metabolic issues.
When we are “just catching up on Slack in bed”, we’re essentially throwing our entire circadian system off-balance, which would eventually show up as:
Slower thinking
More emotional reactivity
Less consistent focus across the week
How to use blue light properly
Morning: Within 1–2 hours of waking, get at least 20–30 minutes of outdoor light, even if it’s cloudy. This anchors your circadian clock and supports alertness later.
Workday: Use reasonably bright, blue-enriched or “cool” light during work hours - study shows appropriate use of blue light actually enhances cognitive functions such as attention, alertness, and reaction time.
Evening: About 2–3 hours before bed, reduce blue light aggressively. Dim overhead lights, switch to warmer lamps, use night mode, or wear blue-light-blocking glasses if you must stay on screens.
Sleep environment: Aim for the room to be as dark as practically possible, using blackout curtains. If you or your child needs a night light, keep it low and warm, not bright and blue.
Noise: sensory overload taxing cognitive efficiency
Most founders don’t think there is a link between noise, mental health, and cognitive performance. But chronic noise is now treated as a pervasive environmental stressor in neuroscience.
A 2024 review of noise-induced cerebral alterations found that noise exposure induces neuroinflammation, alters neurotransmission across the cortex, hippocampus, amygdala, and other regions. EEG also shows that different levels and types of noise shift brain activity patterns in ways consistent with reduced attention and cognitive efficiency.
Prolonged exposure to high noise levels is associated with:
Increased stress and cardiovascular risk
Sleep disturbances
Decreased cognitive performance and more errors at work
A 2025 study looked specifically at noise, time pressure, and cognitive load together. All three worsened task performance, increased sensory overload, and heightened fatigue. Interestingly, the impact of noise was powerful in people with higher sensory sensitivity or anxiety, profiles that are over-represented among founders.
Designing a noise budget for your brain
If you feel “irrationally” irritable or exhausted in busy spaces, consider that your brain might be more sensitive to noise.
Here are some simple ways to break the curse:
Noise-cancelling earplugs: get a pair of earplugs designed to protect your hearing at music festivals, and wear them whenever you’re in a crowded place, at events, or feel tired.
Micro-recovery: build in short, true-quiet intervals (5–10 minutes outside, in a stairwell, or a phone-free room). Our nervous system needs breaks from sensory bombardment as much as it needs breaks from cognitive load.
Key takeaways
Most of us try to improve our performance through willpower and self-talk, but neuroscience says: start a layer beneath that. Air, photons, and soundscapes are constantly nudging your brain toward clarity or confusion, regulation or overload.
If you learnt something new, this week is the week where you take time to make three small, non-sexy decisions about:
How fresh the air is when you make your hardest calls
What kind of light do your eyes see across the day
How much noise your nervous system is expected to absorb
The environment will not build our company for us.
But it does impact how much of our real cognition actually makes it to the table.
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As always, hit reply if something in here hits home.
Until next week,
Lavena
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