Hi {{first_name}} ,

Last week, scientists figured out why: they're growing new brain cells at twice the rate of everyone else.

And the difference? It's not their genes.

For most of the twentieth century, neuroscience had a hard rule. You're born with all the brain cells you'll ever have. After that, it's a slow decline. Textbooks printed it. Professors taught it.

Then the cracks started showing.

In 1998, Eriksson's team found new neurons in adult human brains. Spalding's group later used Cold War nuclear fallout to prove we make about 700 new hippocampal neurons every day.

But the field couldn't agree. A 2018 Nature paper said neurogenesis stops at age 13. One month later, a Cell Stem Cell paper said it continues for life. Same-tier journals. Opposite conclusions.

The problem was the tool. Both sides stained dead brain tissue and looked for proteins in young neurons. Those proteins degrade after death. Different labs, different protocols, different answers.

A paper published last week in Nature just ended the argument.

Ahmed Disouky's team at Columbia didn't use antibody staining at all.

They used a completely different technique: single-nucleus RNA sequencing and chromatin accessibility profiling to read the complete molecular identity of 355,997 individual brain cells from 38 post-mortem hippocampi.

Five groups:

The old method asked: "Is this one protein sitting on the surface of this cell?" The new method asks: "What are all 20,000 genes doing in this cell right now, and which parts of the genome are physically open for business?"

It's the difference between checking address at the door and doing a full-on housing inspection.

They found neural stem cells, neuroblasts, and immature neurons across every age group. Neurogenesis is real. It persists into old age.

But the interesting part is yet to come…

Super agers are people over 80 whose memory performs like someone 30 years younger. Northwestern's SuperAging Program has been studying them for over a decade: thicker cortices, more von Economo neurons (specialized cells for social cognition), larger neurons in the entorhinal cortex. Some have amyloid plaques in their brains and show zero cognitive decline.

They don't avoid the damage. They outrun it.

Disouky's team found:

The mechanism? Epigenetic. Not your DNA sequence, but your chromatin accessibility: the physical switches that determine which genes get read and which stay silent. Epigenetic means modifiable.The preclinical finding that changes the timeline

The researchers detected epigenetic dysregulation of neurogenesis in people with preclinical Alzheimer's. People who had amyloid pathology in their brains but zero symptoms. No cognitive complaints at all.

The switches were already flipping in the wrong direction before anyone, including the patients themselves, knew something was happening.

The window for intervention opens earlier than we thought. And the interventions are things you already have access to.

As a physician and founder of a startup, I place high value on protecting and growing my brain cells; not to mention, this is a priority for many of my patients. Luckily, the research on modifiable drivers of neurogenesis is strong. My protocol is based on the best science out there today.

Aerobic exercise is the most potent known driver of BDNF (brain-derived neurotrophic factor), the molecule that signals your brain to grow new neurons. A 2011 RCT showed one year of moderate aerobic exercise increased hippocampal volume by 2% in older adults, reversing 1-2 years of age-related shrinkage. The control group's hippocampi shrank. A 2025 review mapped the "muscle-brain crosstalk" pathway through which exercise-released myokines signal the hippocampus to produce new cells.

150+ minutes a week of zone 2 cardio. Your hippocampus literally gets bigger.

My version: zone 2 for me is walking on an incline. For higher intensity, I rotate between the Norwegian 4x4 protocol (four intervals of four minutes at near-max effort, three minutes recovery) and REHIT (reduced exertion high-intensity training). REHIT sessions are absurdly short. Two 20-second all-out sprints in a 10-minute workout, and the VO2max data is surprisingly solid. I don't need to love cardio. I just need to do it.

New neurons survive or die based on whether they're recruited into active circuits. Novel learning is what recruits them. Not daily Sudoku (sorry). A new language, an instrument, navigating unfamiliar places.

The discomfort of not knowing something is the biological signal that new neural circuits are being wired. The cognitive enrichment data on novel learning is solid.

I spend hours every day reading longevity science, getting up to speed on AI tools that didn't exist six days ago, and building a company from scratch. If you've ever tried to learn an entirely new field while simultaneously running a startup in it, you know the feeling. There is no shortage of discomfort.

So whether it’s taking a new class or traveling to new environs, try something new that makes you just a little uncomfortable.

Sleep restriction doesn't just make you tired. It kills new neurons. Havekes et al. showed that five hours of sleep deprivation dramatically reduced synaptic connectivity in the hippocampus. A 2024 study found that SIRT6, a longevity-associated protein, mediates the relationship between sleep and hippocampal neurogenesis.

Seven to eight hours. Every night. This is when your brain does its construction work.

This is my biggest challenge, and has been all my life. I have fragile sleep. I wake up early, often hour 5 of sleep, and can't fall back asleep. I track with my Apple Watch and aim for 6.5+ hours, which tells you something about how far I am from the ideal. My setup:

This pattern got noticeably worse after a bad bout of COVID a few years ago, and recovery from any infection takes me a while to bounce back from.

Your supplement stack might be sabotaging your sleep. Worth auditing if you're struggling:

Isolation is neurotoxic. Cinini et al. found that social isolation directly suppressed hippocampal neurogenesis and elevated cortisol. Cacioppo & Hawkley's work on loneliness showed that isolation reduces BDNF and neurogenesis while chronically elevating glucocorticoids.

The Northwestern SuperAging data is consistent: super agers report strong social networks. It's not a soft finding. It's biology.

I'm lucky here. I live and work with my partner (we both work from home, so we spend a lot of time together). I have a dinner group that gets together monthly. And I live in New York, the kind of city where someone is always eager to grab a drink, whether they live here or they're passing through. Social connection is the one intervention on this list I don't have to force myself to do.

A 2024 review found Mediterranean diet components (omega-3 fatty acids, polyphenols) increase neuroplasticity and neurogenesis while reducing neuroinflammation. Intermittent fasting increases hippocampal neurogenesis and upregulates Klotho, the "longevity gene."

I eat a lot of seafood. I supplement with 3-4g of EPA/DHA daily (most people underdose omega-3s). I eat blueberries like other people eat nuts, just constantly. (The polyphenol data keeps getting stronger and I genuinely love them, so this one is easy.) I fast somewhere between 12 and 16 hours most days, but I'm not dogmatic about it.

Cold challenge enhances hippocampal neurogenesis through adrenergic signaling, independent of metabolic effects. Cold water immersion triggers release of norepinephrine, dopamine, and beta-endorphins.

I sauna 2-3 times a week and end with what is called a "sno shower," which 100% is never comfortable. You feel the effects immediately. The norepinephrine hit is real. And despite it never seeming fun, I feel incredible afterward.

The data here is getting hard to ignore.

Psilocybin: Low-dose psilocybin promotes hippocampal neurogenesis and accelerates extinction of conditioned fear. A 2024 study confirmed it reverses stress-induced suppression of neuroplasticity, increasing dendritic spine density and BDNF.

DMT: DMT promotes neurogenesis through the sigma-1 receptor and is produced endogenously in the mammalian brain. We're still figuring out why.

Ketamine: Already FDA-approved (as esketamine) for treatment-resistant depression. Promotes neuroplasticity by raising BDNF, activating mTORC1 signaling, and stimulating hippocampal neurogenesis.

My past company Curio was a psychedelic-assisted therapy company, so I'm biased toward this field. I do use psychedelics, but rarely because I deeply believe in an intentional setting. I'm saving the full deep-dive on psychedelics and neurogenesis for a future issue. Watch this space.

I meditate for 10 minutes every morning. I try to do it before I open my laptop or look at my phone, which is harder than any other intervention on this list. Some mornings I sit with it. Most mornings I fight it the whole time.

Either way, the data says it counts: a MRI review showed mindfulness-based stress reduction produces modest but measurable increases in hippocampal volume.

I grew up playing violin and piano. I don't practice much anymore, but I love music and I'm always exploring new genres. A 2025 systematic review found music training induces neuroplastic changes by modulating neurogenetics and enhancing neurotrophins.

Next month I'm seeing Foxy Shazam, a glam rock band out of Cincinnati that is about as far from classical violin as you can get. The research says novelty matters more than mastery, so I'm counting it 🎸.

If this changed how you think about brain health, forward it to someone who needs to hear it.

The Disouky team detected early epigenetic changes in neurogenesis that were visible in preclinical Alzheimer's patients. People with zero symptoms. The chromatin was already closing in the wrong places before anyone knew something was happening.

That means the window for intervention opens earlier than we thought. And the tools are things you already have access to.

We spent decades telling people their brains were fixed. That cognitive decline was inevitable. Now we have evidence that we might be able to reverse decline via early action.

Your brain is still growing new neurons. The question is whether you're creating the conditions for them to survive.

Keep learning,

Hillary Lin, MD

Follow me for more longevity insights: YouTube | LinkedIn | Instagram | TikTok

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