Episode 79

Four Habits That Keep Your Brain Young

13:10 November 3, 2026 By Dr. Ravi Kumar MD
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Show Notes

Open the skull of a healthy 30 year old and the brain fills the space, plump, pinkish gray, pulsing with every heartbeat. Open the skull of an average 80 year old and the brain has pulled away from the bone. But not every 80 year old brain looks that way.

In this solo episode, Dr. Ravi Kumar, a board certified neurosurgeon, shares what years of operating on and imaging aging brains have taught him. Some older brains look 10, 15, or even 20 years younger than their peers, and the people they belong to tend to share a handful of habits. None of them is a supplement or a hack, and most of them are free.

He starts with the picture most people get wrong. The brain does not shrivel evenly like a piece of fruit. Brain aging is mostly a plumbing problem. The brain is about 2% of your body weight but takes about 20% of your blood flow, and its deep tissues are fed by tiny arteries, some thinner than a human hair, with no backup. When one clogs or leaks, the patch of brain it feeds dies. That is a lacunar stroke, and most of them are silent: no facial droop, no weak arm, just a grain of rice sized spot that shows up on MRI as a bright speck in the white matter. In the Rotterdam Scan Study, about one in five older adults who had never had a stroke had at least one silent infarct, and a 2003 follow up in the New England Journal of Medicine found that silent strokes more than doubled the risk of dementia.

The second change is shrinkage. After about age 60 the brain loses roughly half a percent of its volume per year, and the hippocampus, the memory center, shrinks a little faster than the rest. Ravi also explains a consequence of shrinkage that is a huge part of his job: as the brain pulls away from the skull, the bridging veins stretch like guitar strings, and a minor fall or even a hard sneeze can tear one and start a subdural hematoma. A shrunken brain plus a blood thinner is the number one setup.

Then come the four things he sees in younger looking brains. First, well controlled blood pressure, which he calls the single biggest lever you can pull. The SPRINT MIND trial randomized about 9,000 people to a systolic target under 140 or under 120, and the intensive group had a 19% lower rate of mild cognitive impairment and fewer new small strokes on MRI. Second, a strong body. In a 10 year study of identical twin women, the twin with more leg power had better cognitive aging and less brain shrinkage, and a 2011 trial found that a year of brisk walking grew the hippocampus by about 2%, roughly reversing one to two years of normal aging. Third, good hearing. The Lancet Commission ranks hearing loss among the biggest modifiable risk factors for dementia, and in the ACHIEVE trial, hearing aids slowed cognitive decline by roughly 48% over three years in older adults already at higher risk. Fourth, deep sleep, when the glymphatic system opens up and washes metabolic waste, including the proteins that build up in Alzheimer’s disease, out of the brain.

Episode Resources

In this episode, you will discover:

  • Why brain aging is mostly a plumbing problem: Your brain is about 2% of your body weight and takes about 20% of your blood flow, and its deepest tissues depend on hair thin arteries with no backup supply
  • What a silent stroke is: A lacunar stroke the size of a grain of rice that you never feel, but that shows up on MRI as a bright speck called a white matter hyperintensity
  • How common silent strokes really are: About one in five older adults in the Rotterdam Scan Study had at least one, and having them more than doubled the risk of dementia
  • Why memory goes first: After about age 60 the brain loses roughly half a percent of its volume a year, and the hippocampus shrinks faster than the rest
  • The hidden danger of a shrinking brain: Stretched bridging veins tear easily, which is why a minor fall or hard sneeze can cause a subdural hematoma, especially in someone on a blood thinner
  • What the SPRINT MIND trial found: Targeting a systolic blood pressure under 120 instead of 140 lowered the rate of mild cognitive impairment by 19% and slowed the buildup of small strokes
  • Why leg strength predicts brain health: In identical twin women followed for 10 years, the twin with more leg power had better cognitive aging and less brain shrinkage
  • How walking grew the memory center: A year of brisk walking three times a week increased hippocampal size by about 2%, while the stretching group’s hippocampus shrank
  • BDNF, the fertilizer for your neurons: Exercise releases brain derived neurotrophic factor, a likely link between a strong body and a healthy brain
  • Why hearing loss is a brain problem: Lost sound input, the extra effort of decoding speech, and social withdrawal all take a toll, and the Lancet Commission ranks hearing loss among the biggest modifiable dementia risk factors
  • What the ACHIEVE trial showed: Hearing aids slowed cognitive decline by roughly 48% over three years in older adults already at higher risk
  • How deep sleep cleans your brain: The glymphatic system opens during deep sleep and flushes out metabolic waste, including the proteins that pile up in Alzheimer’s disease

Key Takeaways

Know your blood pressure, then control it. High blood pressure over decades thickens, stiffens, and eventually clogs or ruptures the tiny arteries that feed the deep brain. It is the single biggest lever you can pull for brain health.

Keep your body strong. The brain runs on the same blood supply as your muscles. Strength and regular walking protect brain volume, reduce falls, and improve overall metabolic health.

Get your hearing tested. Hearing loss is a brain input problem, and it is completely modifiable. If your hearing is impaired, fix it, because staying connected to conversation and to other people protects your brain.

Protect your deep sleep. Sleep is not just rest. It is active maintenance, the time when your brain washes itself out.

Cover the basics too. If you smoke, stop. If you have prediabetes or diabetes, get your metabolic health in line. Treating your body well treats your brain well.

Transcript

[00:00 –> 00:14] Dr. Ravi Kumar: I’ve had my hands inside more human skulls than I can count. And there’s one thing I’ve never gotten used to. When you open the skull of a healthy 30 year old, the brain just fills the space. It’s plump. It pulses with every heartbeat.

[00:14 –> 00:46] Dr. Ravi Kumar: The surface of the brain is bright pinkish gray, and the blood vessels on the top of it look like beautiful fresh rivers of blood. Now open the skull of an average 80 year old, and the brain has pulled away from the inside of the skull, leaving a gap. The folds on the surface have gotten deeper and the ridges of the brain have gotten thinner. And then when we look at the MRI, the deep white matter parts of the brain, which is the wiring of the brain, is speckled with little bright spots that were not there 40 years ago. Okay.

[00:46 –> 01:11] Dr. Ravi Kumar: So here’s the part of that observation that could be very useful. Not every 80 year old brain looks that way. Some of them look 10, 15, or 20 years younger than their peers. And over the years, I’ve started noticing that people with younger looking brains were doing a few specific things. They weren’t supplements, they weren’t hacks, but instead they were something super simple, super accessible, and in most cases free.

[01:12 –> 01:36] Dr. Ravi Kumar: Stay with me and I’ll tell you how to bring this same set of circumstances into your own life. My name is Dr. Ravi Kumar. I’m a board certified neurosurgeon and in this episode, I’m gonna show you what aging actually does to the brain. I’m gonna talk about the four things I see over and over in brains that actually stay young as the person ages. And I’m gonna tell you how you can apply these habits to your own life.

[01:36 –> 01:53] Dr. Ravi Kumar: And let me give you a quick disclaimer before we get into it. I’m a doctor, but I’m not your doctor. This video is for informational purposes only, and it’s meant to help you ask better questions and work with your own doctor. Also, this show is separate from my role as assistant professor at UNC. Okay.

[01:53 –> 02:11] Dr. Ravi Kumar: So let’s get started with what actually happens to a brain as it ages. Because most people have the wrong picture in their head. People imagine the brain aging like a piece of fruit, kind of like it’s shriveling evenly on the outside. But that’s not what happens. Brain aging is mostly a plumbing problem.

[02:11 –> 02:36] Dr. Ravi Kumar: Your brain is about 2% of your body weight and it takes about 20% of your blood flow. It’s the most oxygen and nutrient hungry organ you have. And it’s fed by a network of tiny arteries, some of them thinner than a human hair that dive down deep into the brain bringing nutrients to vital deep tissues. And those little vessels are very vulnerable. They have no backup.

[02:36 –> 02:56] Dr. Ravi Kumar: If one of them clogs or leaks, the patch of brain that it was feeding actually dies and nothing else steps in to feed it. That is what we call a lacunar stroke, which is essentially a tiny stroke in your brain. Now, most of those little strokes are silent. You don’t feel them. There’s no face drooping, no arm going weak.

[02:56 –> 03:15] Dr. Ravi Kumar: It’s a spot the size of a grain of rice in a part of the brain that has some redundancy. So in most cases, you don’t notice it. But if you get an MRI, doctors like me will see them. Those bright speckles I mentioned, we call them white matter hyperintensities. And they are essentially little dead spots in your brain.

[03:15 –> 03:36] Dr. Ravi Kumar: So you might be thinking, well, that’s super rare and I probably don’t have to worry about it. And that’s where you’re wrong. It turns out they’re fairly common. In one of the big population studies out of the Netherlands, the Rotterdam Scan Study, about one in five older adults who have never had a stroke had at least one silent infarct on their scan. That’s 20% of the people.

[03:37 –> 04:05] Dr. Ravi Kumar: And a follow-up study published in the New England Journal of Medicine in 2003 found that people with silent strokes had more than double the risk of going on to develop dementia. So when I look at an aged brain on an MRI and I see that speckled white matter, what I’m really looking at is decades of small vessel injury that’s taking away a little bit of precious brain with each stroke. Okay. So that’s the first thing I noticed in aging brains. The second thing I’ve noticed is shrinkage.

[04:05 –> 04:35] Dr. Ravi Kumar: After about age 60, the brain loses somewhere around a half a percent of its volume every year, give or take. The hippocampus, which is your memory center right here in the deep part of the temporal lobe, shrinks a little faster than the rest. That’s why memory loss tends to be the first thing a person notices. Also, I wanna mention here that there’s another consequence to brain shrinkage that most people never think of, but it’s a huge part of my job. When the brain shrinks, it pulls away from the skull.

[04:35 –> 05:02] Dr. Ravi Kumar: The veins that bridge the gap between the surface of the brain and out to the lining of the skull, they get stretched like guitar strings. And a stretched vein tears easily. So a minor fall, a bump against a cabinet door, or maybe just a really hard sneeze can tear one of those veins and start a slow bleed on the surface of the brain. We call it a subdural hematoma. It’s one of the most common operations I do on older adults.

[05:02 –> 05:17] Dr. Ravi Kumar: And the number one set up for a subdural hematoma is a shrunken brain plus a blood thinner. Okay. So that’s the anatomical picture. Aging is basically small vessel damage plus brain shrinkage. Now, let me tell you about the brains that don’t look like that.

[05:18 –> 05:44] Dr. Ravi Kumar: So over a lot of years and a lot of patients, I’ve noticed certain qualities of my patients that led to healthier looking brains. And I should say that these observations are also backed by the scientific literature. The first thing is that younger brains almost always belong to people with well controlled blood pressure. This is probably the single biggest lever that you can pull to protect your brain. And the rationale here is common sense.

[05:45 –> 06:05] Dr. Ravi Kumar: Remember those tiny hair thin arteries feeding the brain? Well, high blood pressure over decades shears the inside of those vessels. It thickens their walls, stiffens them, and eventually clogs them or blows them out. The trial that proved this is called SPRINT MIND. It was published in JAMA in 2019.

[06:05 –> 06:44] Dr. Ravi Kumar: They took about 9,000 people age 50 and older with high blood pressure and randomly assigned them to either standard target, which is a systolic blood pressure under 140 or an intensive target, which is a systolic blood pressure under 120. The intensive group had a 19% lower rate of mild cognitive impairment, which is the stage right before dementia. And when they looked at the MRI substudy, the intensive group accumulated less of those tiny strokes over the following years. So when a patient asks me what’s the number one thing that they can do to protect their brain? I tell them first, stop smoking and control your diabetes.

[06:44 –> 07:00] Dr. Ravi Kumar: And second, control your blood pressure. If you don’t know what your blood pressure is, you need to know it and then you need to control it. Okay. So on to the second thing that I’ve noticed in people with healthy brains. People with young brains still look and act strong.

[07:00 –> 07:26] Dr. Ravi Kumar: I mean physically strong. This one surprised me when I first noticed it because I’ve always thought of the brain and the body as sort of separate departments, but they’re not. The brain runs on the same blood supply the muscles do, and the thing that keeps that blood supply healthy is movement. There’s a study I love from the Journal of Gerontology in 2016 that followed identical twin women for 10 years. This is called a twin study because it controls for genetics.

[07:26 –> 07:46] Dr. Ravi Kumar: Because identical twins have the same genes. And in this study, the twin with more leg power at the start had better cognitive aging and less brain shrinkage a decade later. They had the same DNA. But different leg strength meant a different cognitive destiny. And there’s actually a mechanism that explains this.

[07:47 –> 08:22] Dr. Ravi Kumar: When you exercise, your muscles and your brain release a molecule called BDNF, which stands for brain derived neurotrophic factor. A lot of people call BDNF fertilizer for your neurons. A randomized trial published in 2011 took older adults and had half of them walk briskly three times a week for a year and half of them do stretching. The walking group had their hippocampus, which is the memory center in their brain, increase in size by about 2%. In the stretching group, well, their hippocampus shrank, which is what normally happens at that age.

[08:23 –> 08:51] Dr. Ravi Kumar: So 2% doesn’t sound like much until you realize that it’s the equivalent of reversing one to two years of normal aging just from walking. And that goes back to maintaining a healthy strong body and it likely connects with this molecule BDNF. So people with healthy brains are strong, healthy, and active. Okay. So the third thing I noticed was that people with young brains could hear well.

[08:51 –> 09:29] Dr. Ravi Kumar: And this is something you notice easily when you work with older patients. You either have to shout for them to hear you or you can talk at a nice normal voice level. And I noticed a connection here with who could hear well and who had healthy brains. Now stay with me on this one because it sounds like it came out of nowhere but in 2020 and again in 2024, The Lancet Commission on Dementia went through all the risk factors that you can actually change and they ranked hearing loss as one of the biggest modifiable risk factors in the world for reducing your dementia risk. So why would correcting your hearing reduce your dementia risk?

[09:29 –> 09:56] Dr. Ravi Kumar: Well, there are a couple possible reasons for this. When your hearing goes, the parts of your brain that process sound stop getting input. An unused brain shrinks just like muscle shrinks when you don’t use it. On top of that, your brain has to work harder to decode every conversation when there’s not proper audio input, meaning you have hearing loss. And that effort to decode that low signal gets stolen from memory and thinking.

[09:56 –> 10:21] Dr. Ravi Kumar: And the biggest reason for why I think hearing plays an outsized role in brain health is that when people can’t hear properly, they withdraw from the world. They stop socializing because socializing is exhausting when you can’t hear properly. And social isolation is on its own a risk factor on par with some of the most deleterious habits out there. So that’s all scary. But here’s the good news.

[10:21 –> 10:41] Dr. Ravi Kumar: And this is recent. A randomized trial called ACHIEVE, published in The Lancet in 2023 gave hearing aids to older adults with hearing loss. And in the group that was already at higher risk for cognitive decline, hearing aids slowed that decline by roughly 48% over three years. Okay, so on to the next thing. Number four.

[10:41 –> 10:59] Dr. Ravi Kumar: The people I’ve seen with younger looking brains have had good sleep habits. They prioritize real deep sleep. I’ll keep this one short because I’m gonna do a whole separate video on it. But the headline is this. During deep sleep, your brain physically flushes itself out.

[10:59 –> 11:30] Dr. Ravi Kumar: There’s a plumbing system called the glymphatic system that opens up when you’re in deep sleep and washes out the metabolic waste, including the proteins that pile up in Alzheimer’s disease. When you skip deep sleep, those proteins don’t get washed out and they get stuck in the tissue of the brain itself. So sleep isn’t just rest for the brain, it’s actually active maintenance. And the people whose brains looked younger, almost without exception, were the ones who had the best sleep habits. Okay.

[11:30 –> 11:59] Dr. Ravi Kumar: So with all those observations and the clinical evidence to back it up, what should we change? Well, one, know your blood pressure and get it controlled because that protects those hair thin arteries that feed the brain. Two, keep your body strong because the health of your brain mirrors the strength of your body. When you strengthen your body through exercise, you’re less prone to falls and your overall metabolic health is greatly improved. Three, get your hearing tested.

[11:59 –> 12:27] Dr. Ravi Kumar: And if it’s impaired, fix it because hearing is a brain input problem that’s completely modifiable. And four, protect your deep sleep because that’s when your brain washes itself out. Those are the easy and high yield things you can do to protect your brain. And I would add on to that, if you smoke, stop, and if you have prediabetes or diabetes, get your metabolic health in line. Treating your body well treats your brain well too.

[12:27 –> 12:45] Dr. Ravi Kumar: Okay, that’s it folks. I hope this episode was informative. And if it made you think about a parent, a spouse, or maybe someone who’s suffering with brain health issues, do me a favor and send this to them. Knowledge is power. And the more knowledge you have, the more empowered you are to help take care of yourself or the people you love.

[12:46 –> 13:08] Dr. Ravi Kumar: And remember, also check out my new app, braingamer.app. That’s braingamer.app. This is an app that I designed so that you can intentionally exercise the different domains of your brain and thinking just like you would do a muscle when you go to the gym. So go to braingamer.app and give it a try. Until next time, stay curious, stay skeptical, and stay healthy.

[13:08 –> 13:09] Dr. Ravi Kumar: Cheers.

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