It’s understandable that people often think about their brain as aging separately from their body. It often seems like two different processes.
Getting older usually means getting a little slower, weaker, and heavier; showing a few wrinkles; going gray; and perhaps, if you’re unlucky, developing such debilities as diabetes, arthritis, hearing or vision loss, heart disease, digestive problems, or cancer. On the other hand, a whole different set of issues affect the brain later in life, such as memory problems, dementia, Alzheimer’s disease, Parkinson’s, or other neurological disorders.
The symptoms of body aging and brain aging appear to develop on parallel tracks, independently, and not necessarily at the same time. You can develop dementia even when your body is fine physically, and your body can deteriorate even as your brain stays fully functional and engaged.
But the latest science is squarely focused on the powerful connection between aging of the body and brain, not only as people approach their upper age brackets but also throughout life. How well you care for, listen to, and respond to your body in your 40s, 50s, and 60s is closely associated with how well your brain will function in your final years or decades—and vice versa.
Body and brain are, in fact, on the same track, responding to the same healthy habits and bad behaviors, including these:
But the brain needs extra help, too. It’s also affected by how you actually use your brain when you’re young—what you think, how you feel, and how much you learn. Studies show that cognitive health in later years is also influenced by the following:
To keep your brain from deserting you before the party’s over, you have to take care of your body and your brain. Both can be done, and doing both makes a difference no matter when you start or how incrementally you dive in. But like any savings account, the earlier you get going, the more power you have to put time back on your clock.
“To keep your brain from deserting you before the party’s over, you have to take care of your body and your brain.”
You don’t see yourself aging when you look in the mirror one week to the next, but you know you are aging ever so slowly, even imper-ceptibly. It’s only once in a while that you look at yourself and realize you don’t look—or feel, or think—like you used to. Likewise, when you take small steps to slow down that process, to boost your brain and support your cells, you probably won’t notice the change week to week, but over time, they add up to make a real difference. That’s when you look in the mirror and think, You know, I look pretty good, and I feel pretty good, too.
The science of brain aging has made incredible advances, thanks to imaging technology, which can take detailed pictures of structures in the brain and even which parts of the brain are most active when you’re using it. This has been especially valuable for comparing brain function at different ages. When an older person is asked to do a calculation, for example, a larger portion of the brain lights up than when a younger person performs the same task. The older brain is less efficient, but it compensates by calling on other parts of the brain to step in and help.
It’s a little like lifting an arm chair to move it across the room: a younger person can do it alone using his or her own strength, but an older person needs someone else to help lift the chair and move it.
But brain scans can be maddening, too: they show how much we still don’t know about why and how some people develop memory problems, dementia, and diseases like Alzheimer’s. In theory, if you look at the brain of a cognitively diminished person (the scientific term is demented), it should look different from the brain of a normally functioning individual. The demented brain might be smaller, have sections of dead tissue or holes where brain tissue has dissolved, contain abnormal protein clumps, or some combination of these. But it turns out that the way a brain looks on a scan may not bear any relationship to how functional the owner of that brain really is.
My own father is a good example. He was a brilliant historian, intellectually curious and active, but also deeply engaged in many aspects of culture and life. A year before he died at age 89, I took him to have a brain scan because of severe mobility issues and exhaustion he had developed quite suddenly. The radiologist remarked to my father’s internist that his brain scan looked like that of his own father—who was in the advanced stages of Alzheimer’s disease. Yet there was my father, a little slow and sleepy at times, but otherwise chatting, joking, sharp, and clearly enjoying life. Outwardly, he seemed to be aging pretty well. But his brain scan was far from ideal.
“Outwardly, he seemed to be aging pretty well. But his brain scan was far from ideal.”
“You can have two brains, and they both have lots of Alzheimer’s pathology, but you see that one person was severely demented during life and the other one had no symptoms,” said Dr. William Jagust, neuroscientist at the University of California, Berkeley. “The question is, how can this be?”
The emerging answer is that the brain has something called cognitive reserve. Essentially, this is the brain’s ability to keep functioning despite deterioration. Cognitive reserve is like the brain’s built-in backup system. It allows the parts of the brain that aren’t damaged to take over for the parts that are. To understand how that happens, it helps to know a little bit about the biology of the human brain.
It may weigh only 3 pounds, but a person can have a hundred billion nerves cells, called neurons, in the brain, and a quadrillion points of connection among those cells. It’s those connections, like a computer motherboard, that power all your thinking, analyzing, dreaming, remembering, smelling, seeing, moving, and breathing.
Neurons are specialized cells that look kind of like trees: one end holds a bunch of branches like the crown of a tree. The middle section is like a long, thin trunk. And the far end has more branching but is less dense—more like the roots of a tree. Neurons communicate by sending tiny, electrically charged molecules across gaps (or synapses), where the branches of one tree (called dendrites) meet the roots (or axons) of the next tree. These electrochemical signals power your life.
Some people have more nerve endings in their brains than other people. They may have more neurons—essentially a thicker forest with more trees—or they may have especially dense, complex branching at the ends of each nerve, like the top of a big, healthy shade tree.
But some people have fewer neurons and a looser structure of nerve endings, like a tree that lets lots of sunshine through. With fewer neurons and nerve endings, the brain has fewer overall connections.
These structural differences are at the heart of cognitive reserve and help explain why some people’s brains are more or less vulnerable to cognitive decline. As we age, the branches of nerve endings in our brains gradually get pruned back—by disease, by injury, or simply by lack of use. It happens to everyone.
But if you have a lot of connections to begin with, you’ll have more connections left, even after years of pruning. This is how Dr. Paul Nussbaum, clinical neuropsychologist at the University of Pittsburgh Medical School, explains it: “If you think of Alzheimer’s as a weed whacker, it’s going to take a whole heck of a lot longer to get through a jungle than through a few palm trees.” Those remaining undamaged parts of the brain are your cognitive reserve, and they can pick up the slack for the parts that are damaged.
The brain does not just accept all the age-related deterioration it experiences without fighting back. It has various defense mechanisms, such as proteins that generate neuron growth in response to certain behaviors like exercise. But the most common defense against cognitive decline is that the brain figures out a workaround.
“The brain does not just accept all the age-related deterioration it experiences without fighting back.”
If a young, healthy person’s brain sends a signal directly from point A to point B, for example, an older person might have to make that same communication by sending a signal first from A to C and then from C to B. That’s why more of the brain lights up in the MRI of an older person performing a thinking task.
“They are bringing different parts of their brain online,” Jagust explains.
It may be a sign of inefficiency and age, but when a bigger portion of an older brain lights up when performing a task, it’s also a great sign of resilience. The more healthy neurons a person’s brain can call on to perform a workaround, answer a question, or recall a memory, the longer that person will be able to function independently and enjoy life.
If everyone has at least some deterioration in their brains as they age, then everyone needs plenty of cognitive reserve.
So how do you get it?
The biggest factor influencing cognitive reserve may be one that you can’t do a whole lot about at this point: a higher level of education. All that time spent learning when you were young actually built brain tissue, one connection at a time. Although much of the brain’s growth stops in your 20s, every time you learn something new—and this is true throughout life—that learning stimulates new pathways between neurons to encode and remember that bit of knowledge, that face, or that experience. Learning can even cause the generation of completely new neurons.
This helps explain why someone like my father, highly educated to begin with and extremely intellectually active throughout life, kept much of his cognitive ability until shortly before he died. As kids, my sister and I used to joke that he had a big brain, and that’s why hats were often too small for him. We didn’t know how right we were!
Consider a study done by researchers in Germany, who used MRI scans to measure the brains of medical students before and after studying for exams. After months of intense studying, the researchers reported in The Journal of Neuroscience in 2006, the amount of gray matter in the students’ brains had “increased significantly.”
“After months of intense studying, … the amount of gray matter in the students’ brains had ‘increased significantly.’”
Other studies have shown increases in brain size from consistent learning and practice of various tasks, including learning to play an instrument, speak a new language, or even juggle! Chinese researchers published a study in 2011 in the journal Proceedings of the National Academy of Sciences showing that changes can be seen in as little as a few hours of intense learning. The researchers used MRI scans to measure the brains of adult subjects before almost 2 hours of learning new color names and found an increase in the volume of gray matter in the left visual cortex of the subjects’ brains, which is the area responsible for discerning color vision.
As important as learning is, we can’t spend all our days in the library, so luckily, other factors also appear to affect cognitive reserve throughout life. Among the most important are having a large network of close friends, physical activity, physical health, cognitive engagement, and a sense of purpose in life. These are some of the main factors observed by neurologist Dr. David Bennett, director of the Alzheimer’s Disease Center at Rush University Medical Center in Chicago.
Dr. Bennett heads up two large population-based studies looking at the causes and conditions of dementia and other kinds of cognitive impairment. One involves about a thousand Catholic clergy, nuns and brothers, while the other follows regular individuals from the community, for a total of about 2,700 people. Everyone entered the study at about age 70 or older, and none had dementia at the outset. All participants also agreed to be regularly evaluated for cognitive decline and then donate their brains to science after their death.
Clock-Cheater Tip
It almost doesn’t matter what you learn; it will benefit your brain. But even better is discussing what you’ve learned with someone else. Some great ways to do that include joining a book club, taking a continuing education seminar at the local university or community college, or taking a class with a chatty friend or two so you’re not just learning but also socializing as you learn.
So far, hundreds of participants in the two studies have developed Alzheimer’s disease, and Bennett’s team has performed more than 1,000 autopsies. Not one brain at the time of death (average age, 87) appeared normal, even though many subjects had displayed normal cognitive function when they died. Bennett has sorted through waves of data analyzing various aspects of these people’s lives to draw conclusions about what factors influence a person’s rate of cognitive decline, such as activity level, personality, physical health, genetics, and life experience.
Some factors seem to make an aging person do worse in general, no matter what or how severe the existing brain problems might be. Depression does that, for example. Other factors seem to make people do better overall, regardless of underlying pathology, such as general happiness. These factors are a little mysterious because they seem to operate independently of anything else going on in the brain, “like a proxy for something we haven’t measured, either good or bad,” Bennett says.
But what has clearly emerged from Dr. Bennett’s research is the strongly positive effect of having a large social network, especially in people with clear evidence of disease in their brains.
“Social networks is where I’ll ask you how many people, other than your spouse and children, do you feel comfortable talking to and confiding in. Not Twitter or Facebook friends, but the number of people [who], if you had a problem, you could call and rely on. That’s your network,” Bennett says. “It’s such a simple concept, but it turns out to be remarkably predictive of all kinds of things.”
The bigger a person’s social network, the more resistant they are to the effects of brain disease, Bennett says. “It somehow changes the way your brain is responding to the pathology,” he says.
It’s not really clear why, but neuroscientists like Bennett and Jagust believe it makes sense. “If you think about what your brain was developed for, it was developed for social interaction,” Jagust says. So from an evolutionary perspective, creating a strong network of friends should enhance overall survival.
“From an evolutionary perspective, creating a strong network of friends should enhance overall survival.”
Exactly what the mechanism is that controls this isn’t known, but Dr. Bennett thinks it might be that making friends—and keeping them—is a challenge, and the brain responds to a challenge by activating all kinds of growth systems and protective measures. Education does that, too, since it clearly is a challenge when you work hard to understand and remember facts, ideas, theories, and solutions.
“It’s hard to build a large social network—you’ve got to nurture it, you’ve got to be able to deal with all kinds of other people,” Bennett says. Doing so, it seems, builds a denser, more resilient brain.
Other cognitive factors that protect your brain over time include the following:
Thinking more: Reading, writing, doing puzzles, playing games—anything that makes your brain work harder increases blood flow to it, bringing oxygen and nutrients that help keep existing connections in place.
Being socially active: Not only does this help build your network of friends, but it also exposes your brain to new experiences and ideas, which—you guessed it—builds and preserves connections in your brain.
Finding something meaningful in life: Having a sense of purpose seems to bring together many of these other factors: it gets you out of the house and exposed to new situations, it makes you interact with others, and it improves your outlook, which decreases the negative effects of depression.
Do Brain-Exercise Programs Work?
There’s much conflicting evidence about the kinds of brain-athletics programs being sold today as a way to keep your brain young. Certainly, scientific evidence suggests that using your brain and thinking more in any way is good for you. So in that way, these programs are doing some good. But do memory exercises actually improve your memory? That’s not so clear. Some scientific studies have shown that doing certain cognitive training exercises only make you better at that cognitive exercise, but there’s little “generalization” to the real world, according to neuroscientist Dr. William Jagust at the University of California, Berkeley. On the other hand, some studies show there is some benefit to everyday life. “The jury is still a little out on this,” Jagust says. “There’s no evidence that it … protects from Alzheimer’s.”
Of course, there also can be a strong component of genetics in someone’s risk of developing dementia. There are, for example, variants of a particular gene, called APOE e4, that increase a person’s risk of developing cognitive impairment. Early onset Alzheimer’s disease can run in families, too. Some scientific studies have shown that dietary interventions on such genetically inclined individuals are not effective. On the other hand, those Scandinavian research projects on identical twins suggests that genetic factors can, in fact, be mitigated by a healthier lifestyle.
But for the vast majority of people, it is behavioral, cognitive, and dietary habits that make the big difference—which means positive interventions can really work.
Small changes made over a long period of time can help your brain weather the inevitable changes that come with age—maybe even in people with an unlucky genetic blueprint.