Stay Sharp
Five things to do now so your brain still works later
Here is a number that should reshape how you think about longevity: up to 45% of dementia cases worldwide may be preventable or delayed. Not through genes (we’ll get there)...through how you sleep, move, eat, breathe, hear, see, think, and connect.
That is the headline finding of the 2024 Lancet Commission on Dementia, one of the most respected ongoing assessments of cognitive decline in the world. It is the number I would put at the top of every brain longevity conversation, because it changes the script. Cognitive decline is not the genetic slot machine most of us were raised to think it was. For roughly half the population, it is downstream of how we live.
Living a long time is not actually the goal. Living a long time as yourself is.
The other thing worth knowing up front is this: early intervention is everything (yes, yes it is). The Lancet data is clear that addressing modifiable risk factors in midlife has the biggest impact on dementia risk decades later.
The five things I’ll share today only compound if you start them while you still have the runway. Forty-five percent of dementia is preventable, but only if you begin before the symptoms arrive.
So today, five things to do now. What each one is doing under the hood, and the science behind each.
1. Sleep (if you’ve been with me a minute, you’ll sense a theme here)
Your brain has a dedicated waste-clearance system, the glymphatic system, that essentially does not turn on until you are in deep sleep. It is what flushes beta-amyloid and tau (the proteins associated with Alzheimer’s) out of your brain tissue every night. Miss the deep sleep window and the trash, literally, piles up.
The protective sleep math is quite simple: most of your deep sleep happens in the first half of the night. Going to bed at 10pm and sleeping seven hours gives you more glymphatic activity than going to bed at midnight and sleeping eight.
Try this:
Bedtime before 10:30 most nights, even on weekends
Cool bedroom (65 to 68 degrees)
No alcohol within three hours of sleep
Magnesium glycinate or threonate at night
If you are not measuring your deep sleep, this is the single best reason to start
In plain English: If you do one thing for your brain this year, get the first three hours of your sleep right. The brain only cleans itself when you are unconscious.
2. Move (the BDNF lever)
The brain protein you should know about is BDNF, or brain-derived neurotrophic factor. Some researchers call it Miracle-Gro for the brain. It supports neuron survival, the formation of new neural connections, and the birth of new neurons in your memory headquarters.
Exercise drives BDNF up, and the research keeps getting more specific about which kind. A 2026 UCL study found that 12 weeks of cycling in previously sedentary adults made their brains release more BDNF per workout. Their baseline did not change much; their spike per workout did. So, the fitter you get, the more brain reward you earn per session.
A 2023 study found that six minutes of high-intensity cycling raised BDNF four to five times more than the same duration of low-intensity work.
Try this:
Resistance training two to three times a week (heavier than you think you should)
Zone 2 cardio (conversational pace) two to three times a week
One short hard intervals session a week (assault bike sprints, hill repeats, anything 30 seconds on, two minutes off)
An outdoor walking habit.
In plain English: Exercise is one of the only inputs that compounds in your favor. The fitter you get, the more your brain rewards you per workout. Just remember to build in rest and recovery!
3. Breathe (the vagus nerve lever)
Your parasympathetic nervous system (the calm, recover, repair branch) runs primarily through the vagus nerve. When the vagus is doing its job, your HRV is higher, your inflammation is lower, your sleep is deeper, and your brain is in a state more conducive to learning and emotional regulation. (Deeper dive on that here.)
The fastest way to stimulate the vagus nerve is breath. Slow, deep, diaphragmatic breathing (5 to 6 breaths per minute) directly raises parasympathetic tone, often within minutes. A 2023 meta-analysis found that brief daily breathwork practice measurably improved anxiety, emotional regulation, and cognitive clarity.
This is, by a wide margin, the cheapest brain intervention available to you.
Try this:
Box breathing (4 in, 4 hold, 4 out, 4 hold) for two to four minutes when you feel wound up
The physiological sigh (two quick nose inhales, one long mouth exhale) when you need to drop your heart rate fast
A short breathwork practice before sleep
In plain English: Breath is the only autonomic function you can voluntarily control. Use it. Two minutes of slow nasal breathing is the cheapest brain medicine you will ever take.
4. Fuel (the gut-brain conversation)
Your gut and your brain are in constant chemical conversation. The microbes in your digestive tract produce neurotransmitters (serotonin, GABA, dopamine), influence inflammation, and shape the integrity of the gut barrier. A gut microbiome under chronic distress shows up as brain fog, low mood, and, over time, neuroinflammation.
The good news: the diet that supports your brain is the same one that supports your metabolism, your cardiovascular system, and your microbiome. The Mediterranean-MIND pattern has the strongest dementia-prevention data of any eating style studied.
Try this:
A wide rotation of plants every week (leafy greens, herbs, root vegetables, polyphenol-rich berries).
Prebiotic foods to feed the bacteria you want (leeks, onions, garlic, green bananas, Jerusalem artichokes)
Resistant starch from cooked-and-cooled potatoes, rice, and oats
Protein at every meal (this matters more in your forties than it did in your twenties)
Olive oil and fatty fish as the dominant fats
Ultra-processed foods kept to a minimum
A note for the histamine-sensitive crowd: fermented foods get a lot of press in the gut-health world, and for many people they are great. For others (hi there!), they make things worse. The smarter bet for that group is prebiotic-rich plants and resistant starches.
5. Stretch your comfort zone (the neuroplasticity lever)
This is the one that sounds the softest and is, in my reading of the research, the most chronically underestimated.
Your brain stays sharp the same way your muscles stay strong: it has to be loaded. Comfortable cognitive routine (the things you already know how to do well) does not build cognitive reserve. Effortful learning does. The kind where you are bad at something, you struggle, you feel a little dumb, and over weeks you get better.
The FINGER trial, one of the most influential dementia prevention studies of the last decade, combined cognitive training with exercise and diet and found measurable improvements in executive function and brain volume in older adults. The cognitive piece was not crosswords. It was structured, progressive challenge.
Try this:
Be a beginner at something at least once a year. (Mine is currently understanding second-grade math…when did we stop carrying the 1?)
Read books on subjects you find slightly intimidating
Real conversations with real friends, in person, regularly. Social isolation is one of the biggest dementia risk factors on the Lancet list.
Stop the mindless scroll. Your brain is not getting better at TikTok.
Pair the new skill with movement if you can (juggle, dance, tennis, pickleball, a martial art).
In plain English: Cognitive reserve is built the same way physical reserve is built. By loading the system. The thing that frustrates you a little bit today is the thing that protects you in your eighties.
The genetic wildcard
Let’s address the one thing people familiar with the topic bring up with brain longevity: ApoE type, especially 4.
ApoE (apolipoprotein E) is a gene that helps your body manage cholesterol, including in your brain. It comes in three flavors: ApoE2, ApoE3, and ApoE4. Most people carry two copies of ApoE3, which is the neutral, common version. Roughly 25% of the population has one copy of ApoE4. About 2 to 3% have two copies.
The issue: carrying one ApoE4 copy roughly triples your lifetime risk of Alzheimer’s. Carrying two copies raises it by approximately tenfold.
That sounds like a sentence designed to ruin your afternoon, but it is not.
Let’s change the framing: ApoE4 increases risk. It does not determine outcome. Plenty of ApoE4 carriers reach their nineties cognitively intact, and the things that protect them are the same five inputs we just walked through.
The good news: you can find out where you stand with a blood test. LabCorp and Quest Diagnostics both offer ApoE genotyping (around $200, ordered through your doctor), and a number of direct-to-consumer companies now bundle ApoE testing with p-tau217, a newer plasma biomarker for amyloid pathology, for under $700. One important caveat: p-tau217 is FDA-cleared for symptomatic adults 55 and older, not as a general screening test for healthy people. If you want to test, do it with a physician who can interpret the results in context.
There is one twist worth knowing if you have done genetic testing and learned you carry ApoE4. Omega-3 fatty acids, specifically DHA, may matter more for you than for non-carriers.
ApoE4 carriers have been shown to have impaired DHA transport into the brain and lower brain DHA levels at baseline. Recent studies suggest they need significantly higher omega-3 intake to see the same cognitive benefit non-carriers get from a standard dose. The clinical research is still emerging, but the practical takeaway is that ApoE4 carriers should consider:
Higher-dose, high-quality fish oil or algae oil (2 to 4 grams of combined EPA/DHA daily, ideally weighted toward DHA)
An Omega-3 Index test to confirm your blood levels are actually in the protective range (target above 8%)
Fatty fish (salmon, sardines, mackerel) at least two to three times a week
A conversation with a longevity-focused physician about whether higher dosing makes sense for you
For non-ApoE4 carriers, the standard 1 to 2 grams of EPA/DHA daily is still a smart bet for cardiovascular and cognitive health, but the dose-response curve is less steep.
In plain English: ApoE4 is the gene most often associated with Alzheimer’s risk, but it is a risk multiplier, not a sentence. The five lifestyle levers above still work. If you carry it, ask your doctor about higher-dose omega-3s and getting your Omega-3 Index measured.
Two bonus risk factors worth a special mention
The Lancet Commission added two factors to its list in 2024 that are easy to overlook:
Hearing loss. Untreated hearing loss is now considered one of the biggest modifiable dementia risk factors in midlife. If you are over 50 and have not had a hearing test in a few years, book one.
Vision loss. Same logic, different sense. Untreated cataracts, uncorrected vision, undiagnosed macular degeneration all reduce the sensory input your brain depends on to stay engaged with the world. Get the annual eye exam.
These are not later-in-life add-ons. They are part of the longevity stack now.
In Case You Skimmed
Up to 45% of dementia cases are potentially preventable or delayable, per the 2024 Lancet Commission.
Early intervention is everything. Midlife (18-65) is when modifiable risk factors have the biggest impact.
The five inputs that matter most: sleep, movement, breath, fuel, and effortful learning.
Sleep activates the glymphatic system, which clears Alzheimer’s-linked proteins. Bedtime before midnight is the lever.
Movement raises BDNF, the protein that keeps neurons alive and growing. Intensity earns more.
Breath is the cheapest brain intervention available. Two minutes of slow nasal breathing measurably calms the system.
Fuel runs through the gut-brain axis. Mediterranean-MIND has the strongest data.
Stretch means effortful learning. Comfort does not build reserve. Struggle does.
ApoE4 is a risk multiplier, not a sentence. You can find out where you stand with a blood test through LabCorp or Quest. Carriers should look closely at higher-dose omega-3s and consider an Omega-3 Index test.
Two underrated risk factors: hearing loss and vision loss. Book the exams.
You probably already do some of these. I suspect most people do. The exercise here is less about adding new things to a life that already feels full, and more about looking at what is already working, what has slipped, and what is worth revisiting. The brain you have in your eighties is the slow accumulation of many, many Mondays of attention, not a single grand intervention. We have a lot of them ahead of us.
See you then,
Susan
Longevity in the Wild
A handful of us, when the planets align between kids and jobs, find our way to my neighbor’s front porch. We sit in her rocking chairs, drink coffee, decompress, and watch the world go by.
I cannot tell you how restorative this is. I also cannot tell you how often it happens, because the answer is approximately whenever everyone’s calendar decides to behave for an hour.
It is the most analog longevity practice I have. It is also, accidentally, hitting every Blue Zone box that science can name: morning light, fresh air, low-stakes time with women I genuinely like, no agenda, no phone. We are not biohacking. We are sitting on a porch.
If you have neighbors and they have rocking chairs, I highly recommend putting them to use.
wait...we no longer carry the 1?!?!