Brainwaves: How does a brain stay healthy? | On Point with Meghna Chakrabarti
This is the fifth episode in 'Brainwaves: Mysteries of the human brain (https://www.wbur.org/tag/brainwaves-on-point).'
You might think a healthy brain starts and ends in your head – but there are miles and miles of neuron fibers that connect your brain with nearly every corner of your body. Why a healthy brain needs a healthy body.
Guests
Jacob Harth, neuroscientist in the College of Public Health at the University of Georgia.
Also Featured
Polina Anikeeva, director, K. Lisa Yang Brain-Body Center at MIT.
Dr. Brad Kuo, chief of gastroenterology at Columbia University and New York Presbyterian hospital.
Dr. Kevin Volpp, scientific lead of the American Heart Association's Health Care by Food Initiative.
The version of our broadcast available at the top of this page and via podcast apps is a condensed version of the full show. You can listen to the full, unedited broadcast here:
Transcript
Part I
MEGHNA CHAKRABARTI: We're at the final episode of Brainwaves. It's our special week looking at the wonderful mystery that is the human brain. And we're going to wrap up the week today with the question that's probably the most pertinent to us all. How do you keep your brain healthy?
Especially as we age. Now, the truth is there's no one magic formula that works for every single person. However, the overall approach actually is quite simple. So then maybe the deeper question for Americans might be, why is keeping our brains healthy getting harder? For example, take dementia. The lifetime dementia risk for American men is as high as 14%.
For women, it's much higher, almost 25%. That's one in four American women. Now, those numbers are from the National Institutes of Health. By the way, NIH also found in a January 2025 study that for all Americans above the age of 55, the risk of developing dementia in a person's lifetime has risen to 42%.
But as they always do, those broad and aggregate numbers are actually hiding something because the risk is not evenly spread across the United States. There are stark regional differences in this country. So if you live in the southeastern U.S, the incidence of dementia is 25% higher than what we see in the Mid-Atlantic.
So to be more clear, if you're in, say, Georgia or Mississippi or Tennessee, the dementia rate is significantly higher than in, say, Virginia. Same goes for the Northwest and Rocky Mountain states. Both of those areas have a 23% higher dementia rate than in Mid-Atlantic states. That's according to a study released just this past summer by the University of California, San Francisco.
Which makes me wonder, not only what can we do as individuals to keep our brains healthy, but what more can we do as a country? Jacob Harth joins us today. He's a neuroscientist at the University of Georgia's Institute of Gerontology, and he joins us from WUGA in Athens, Georgia. Jacob Harth, welcome to On Point.
JACOB HARTH: Thank you. I'm delighted to be here.
CHAKRABARTI: Okay, let's, first off, start off with, how do we define what a healthy brain is? What does it look like? What should it feel like?
HARTH: That's a fantastic question. A healthy brain looks and feels, it can be different for everyone, but it's mostly based on functionality, and we can measure that through behavior.
A healthy brain should be clear thinking and should have steady mood. Should have the ability to attend to things and have strong social engagement. It's not just good memory. There's not one way of measuring or defining brain health. It can be different both across individuals and across the lifespan.
A healthy brain should be clear thinking and should have steady mood.
Jake Harth
CHAKRABARTI: So is it essentially that your brain is capable of letting you do the things you want to do in life, whatever those might be?
HARTH: Certainly. That's a large component of it. Is being able to maintain functional behaviors and have a quality of life that we're looking for.
CHAKRABARTI: So if that's a large component, what are the other components?
We want the whole picture here, Jack.
HARTH: Absolutely. The whole picture, we can get down to minute details about efficiency and connectivity in the brain, but you can also zoom out. And from my perspective in my research, we're often looking at functionality and behavior, and that is oftentimes the main way that we can measure and to track brain health.
CHAKRABARTI: Okay, so give me an example then more specifically of a measure of, let's say, functionality.
HARTH: Certainly. A very common way of measuring functionality is the Montreal Cognitive Assessment, and that's used in neuropsychology to track functionality in daily function.
Ask people about what they can and can't do. But there's also specific measures and things that I can implement in my laboratory that can allow us to look at more specific functions. Things like the efficiency of your processing and specifically how well you can process and how quickly you can process visual information.
CHAKRABARTI: You know what's great about the fact that we have a full hour to discuss things is we can go into a lot of details, so don't be afraid.
HARTH: Absolutely. Alright. Wonderful. Wonderful.
CHAKRABARTI: Yeah don't be afraid. Let's just kick back here and take me inside your lab. So what would be, like what does the actual test look like for the visual processing efficiency you were talking about?
HARTH: That is a great question and I'm very excited to talk about this. I could talk all day.
CHAKRABARTI: Let's go.
HARTH: We've got a whole hour. In my laboratory we measure something called your critical flicker fusion threshold, or CFF is how we often talk about it. And that will tell us about how quickly you can process visual information.
A really good example of this is the screens that are likely in front of us right now. If you're looking at your phone screen or a TV screen or a computer screen, those lights on there are flickering all the time. Our brain can only process flicker at a certain rate.
So have you ever noticed a light bulb starts to die, you start to notice a little bit of flicker.
CHAKRABARTI: Yeah.
HARTH: Or have you taken a video of a phone or a different computer screen.
CHAKRABARTI: And there's a flicker.
HARTH: That's exactly right.
CHAKRABARTI: That you can't see when you're looking at the screen itself.
HARTH: That's exactly right.
CHAKRABARTI: It's the reason movies work, isn't it?
HARTH: That is, because the visual system is sampling over time and it's averaging together the inputs.
So it's giving us this nice, solid, smooth impression of the world. But in reality, there's flicker when we're looking at those screens, those lights, those LEDs are turning on and off at rapid paces. There is some threshold, though, at which point a flickering light starts to look solid to your brain.
And that's what we measure in the laboratory. So we'll take a flickering light and we increase it and increase it until the person tells us, the participant tells us it looks solid to me. And then we'll do the opposite, and that will give us, start off very fast and as soon as they start to notice that flicker again, we'll take that measurement as well. And we'll do that several times and that'll give us an average that will represent that participant's threshold for flicker and that tells us about that flickering threshold.
Your perceptual how fast you can see, how quickly your brain can process visual information.
CHAKRABARTI: Okay. So let me see if I understand this correctly. So then if someone reports that their threshold is actually lower than average, what does that actually mean?
HARTH: That can mean many things, specifically on a day-to-day basis if my flicker threshold is lower than it is on a normal basis, I could just be tired. Maybe it's early in the morning, maybe I've been, maybe it's late in the day, I've been paying attention all day and my brain's gotten tired and I'm losing the ability to focus and to process that visual information.
So it could be a little bit lower, it could vary throughout the day, but if an individual's flicker threshold is much lower than normal that could indicate a lack of efficiency in processing the brain, and that's something that naturally happens throughout the lifespan. There are small decreases in your visual processing speed throughout the lifespan, but if there are sharp or significant decreases in that visual processing speed, that could indicate some greater deficit or issue.
CHAKRABARTI: Okay. Okay. So that's one example of measuring a certain aspect of brain health. And ... we'll get to more aspects throughout the remainder of the show, but I just also wanted to create a baseline here for the discussion regarding what unhealthy brains are like, because of course there's many potential causes. One is just brain injury, which for the purposes of this conversation, even though it's a really important subject, I'm actually going to put brain injury aside. Because that can be sudden and acute.
HARTH: Yes.
CHAKRABARTI: And really instead, over the course of the conversation, what I propose, and you can tell me if this is a terrible idea or not. But I propose on us focusing on degenerative brain diseases and chronic illness ... just because it mostly, it just has an impact on a lot more people.
HARTH: Absolutely. Absolutely.
CHAKRABARTI: But if there's anything that we could learn from brain injuries in the conversation, let me know and we can bring them in.
HARTH: Certainly.
CHAKRABARTI: Oh, go ahead, if I might. Brain injuries, you're absolutely right. They are acute and they have massive impact on long-term brain health.
And we should do everything we can to avoid brain injury, but sometimes we can't. We can really just do our best, wear a helmet when we're in scenarios where we're at higher risk for brain injury, but it's sometimes unavoidable and oftentimes not the fault of the individual.
CHAKRABARTI: Yeah. I just wanted to make that clear. Because I know that many listeners out there either have suffered brain injuries themselves or know someone who has, and I don't wantfolks to think that, like, we're just ignoring that.
It's just, it's such a big topic in and of itself that I wouldn't be able to give it it's due in the course of our conversation.
HARTH: Absolutely.
CHAKRABARTI: Okay then we just have a couple of minutes before our first break, we're going to talk about the effects of chronic disease. We're going to talk about degenerative brain disease, but when we talk about quote-unquote healthy brains, is the baseline of what a healthy brain is, does it change over time? Meaning as we get older, should we just reevaluate what we define as a healthy brain?
HARTH: That's a great question. As we age, there are some normative declines in things like efficiency of functioning, how fast we can see that flicker threshold does decrease, and there are some normative declines in things like memory as well. And what's happening in the brain as we age, is we go from very localized processing, where specific brain regions are accomplishing these specific tasks, to more distributed processing.
Areas in the brain are supporting one another. We have more areas working together to accomplish that same function, that same task. And that can slow things down in some ways and make that processing less efficient. But that's a normal part of aging. And as long as the function and the behavior and the things that we want to do in our life, as long as that remains, it's still a part of normal processing. Oftentimes people will think of cognitive decline or mild cognitive impairment or things like dementia as inevitable, but that's not at all the case. Normal brain aging is healthy brain aging.
Normal brain aging is healthy brain aging.
Jack Harth
Part II
CHAKRABARTI: So Jack, from what I have gleaned in my many years of thinking about trying to keep my own brain healthy and reading various studies, that at the most sort of macro level, here's the sort of general recipe for good brain health.
Okay. And correct me or add anything if is needed.
HARTH: Alright.
CHAKRABARTI: So first of all, sleep enough.
HARTH: Yes.
CHAKRABARTI: Get enough sleep. Exercise is proving to have a very positive impact on the brain.
HARTH: Yes.
CHAKRABARTI: What you eat and trying to reduce stress and keeping your brain socially, keeping social connections strong.
HARTH: Absolutely. Absolutely.
CHAKRABARTI: Would you add anything?
HARTH: I completely agree and I really like those and I want totalk specifically about those things and the ways we can support brain health. And I've actually got an acronym. May I share?
CHAKRABARTI: Yes.
HARTH: So my mom is a high school science teacher, a middle school science teacher. For years and years, she's taught middle schoolers, eighth graders. And in her classroom at the start of the year, make a sign, it hangs up in the classroom the whole year. It says Be SWEET. S-W-E-E-T.
And this is a great way to remember the ways in which we can take care of our brain and promote brain health as we develop and as we age throughout our whole lifespan. But SWEET is our acronym, and it's important in the classroom and in our lives because if we're not taking care of our brains, we can't do anything else. So this is really the foundation for a healthy life. And SWEET. The acronym is S is sleep. That's exactly right. Sleep is not optional. This is the time in which our brain cleans up from the activity of the day and encodes those memories. And that is not optional. If you're feeling tired, always get as much sleep as you can. ... The W is water, so proper hydration. It's critical to go along with that first E, which is eating and proper nutrition. Whole foods, things like fruits and vegetables. Also, healthy fats, things that make up the lipids in our brain and those lipid membranes in our brain. Also eating other healthy foods, whole foods, whole grain, things, fruits and vegetables specifically. That's part of my expertise that I'm excited to talk about. Those are effective antioxidants that can help reduce inflammation and stress in the brain. So there's SWE, the second E is exercise.
You're absolutely right. That's aerobic exercise. Getting out, getting oxygen into our brain and into our circulatory system. What's good for the heart is often good for the brain. And that's not just aerobic exercise, but mental exercise as well. And learning things, trying new skills, novelty and putting effort into brain growth and brain learning is really good for the brain as well. What's good for the heart is often good for the brain.
Jake Harth
And another form of exercise that you mentioned as well is that social exercise, sometimes for introverts like me, it can be difficult to get out and to have that social interaction, but it's very well established that this is a risk for developing cognitive decline later in life, is social isolation.
And the final thing, the T in SWEET is time. Because that doesn't happen overnight. None of these things can happen in a day or a week or a year. This is a lifelong process and each opportunity, each behavior change we make, it takes time and it takes effort. So that is the acronym to 'Be SWEET' to yourself and 'Be SWEET' to your brain.
CHAKRABARTI: Jack, I'm so glad you're in Athens, Georgia right now, but you cannot see the grimace on my face. I think out of the five, I got four strikes.
HARTH: That is quite all right.
CHAKRABARTI: (LAUGHS)
HARTH: And this is other thing that I want to really emphasize, is I'm human and I can preach this all day. I can say take care of your brain, but I fall short as well, a hundred percent.
And making these behavioral changes, eating salads every day and drinking enough water and getting enough sleep. Believe me, I'm often sleep deprived, but these things, they take effort, they take time, and we fall short. We really just have to do what we can and every step, every step. And even the small ones, even me standing up from my desk more often.
Me trying to walk a little bit more instead of driving or taking the bus, every single step is a meaningful step in the right direction towards brain health.
CHAKRABARTI: So folks, I think this is one of the most useful things to actually have come out of On Point in recent memory. Write this down, SWEET. Sleep, water, eating healthy or healthily, exercise, both mental, physical, mental, social and time. And by the way, I think it just makes perfect sense that this wonderful encapsulation came from not only a teacher but a mom as well. Teacher moms are the best. (LAUGHS)
HARTH: Absolutely. I've learned all the most important things.
That's exactly right.
CHAKRABARTI: Okay, so here's the thing. Obviously, the SWEET acronym and this, look at what it takes to keep a healthy brain. It's intrinsically connected to the rest of your body, right?
HARTH: Absolutely.
CHAK
