Brain Rules for Aging Well

10 Principles for Staying Vital, Happy, and Sharp

John Medina

• Publisher: Pear Press
• Year: 2017
• Print ISBN: 9780983263371
• eBook ISBN: 9780998919225
• Topic: Biological Sciences
• Subtopic: Science General
• Index: Biological Sciences

How come I can never find my keys? Why don't I sleep as well as I used to? Why do my friends keep repeating the same stories? What can I do to keep my brain sharp? Scientists know. Brain Rules for Aging Well, by developmental molecular biologist Dr. John Medina, gives you the facts, and the prescription to age well, in his signature engaging style.

With so many discoveries over the years, science is literally changing our minds about the optimal care and feeding of the brain. All of it is captivating. A great deal of it is unexpected.

In his New York Times best seller Brain Rules, Medina showed us how our brains really work, and why we ought to redesign our workplaces and schools to match. In Brain Rules for Baby, he gave parents the brain science they need to know to raise happy, smart, moral kids. Now, in Brain Rules for Aging Well, Medina shares how you can make the most of the years you have left. In a book destined to be a classic on aging, Medina's fascinating stories and infectious sense of humor breathe life into the science.

Brain Rules for Aging Well is organized into four sections, each laying out familiar problems with surprising solutions. First up, the social brain, in which topics ranging from relationships to happiness and gullibility illustrate how our emotions change with age. The second section focuses on the thinking brain, explaining how working memory and executive function change with time. The third section is all about your body: how certain kinds of exercise, diets, and sleep can slow the decline of aging. Each section is sprinkled with practical advice, for example, the fascinating benefits of dancing, and the brain science behind each intervention.

The final section is about the future. Your future. Medina connects all the chapters into a plan for maintaining your brain health.

You may already be experiencing the sometimes-unpleasant effects of the aging process. Or you may be deeply concerned about your loved ones who are. Either way, Brain Rules for Aging Well is for you.

THINKING BRAIN

your stress

brain rule

Mindfulness not only soothes but improves

Some people have told me that I’m grumpy; it’s not something that I’m aware of. It’s not like I walk around poking children in the eye … not very small ones, anyway.

—Irish comedian Dylan Moran

Worrying is like a rocking chair. It gives you something to do, but it doesn’t get you anywhere.

—Anonymous

IF THERE WERE A contest for Most Interesting Man in the World, my grandfather easily could have won. He journeyed to North America as a ship stowaway, complete with an aristocratic Spanish accent, arriving penniless. His mind was well funded, though: rich with humor, radiant as the sunny Meseta Central, blessed with the ability to pick up any language (I lost track at eight). These attributes helped him secure a place in the food industry, working his way to becoming a sous chef at a Detroit country club. He opened a chain of bakeries, raised his family, and died at 101. The last time my wife and I saw him alive—a 100-year-old still in his own home—he showed off his culinary skill. Cheerfully donning his old apron and whistling away, he made six apple pies—at once! Not only was he the most interesting man in the world to me, but he was probably the happiest.

Which is interesting. One might assume that older people would report being quite bothered by life and its attendant changes, more anxious about health and memory and relationship failings, more stressed in general. That is the exact opposite of what researchers find. Older people report being less stressed than their younger counterparts. About 38 percent of all young adults in 2016 (so-called millennials, ages eighteen through thirty-four) report being more stressed than they were the year before. That figure drops to 25 percent with the baby boomers, people born between 1945 and 1960. That number shrinks to 18 percent in the so-called Greatest Generation (parents of the boomers), the lowest figure for any group. And they aren’t just less stressed. As we saw in the last chapter, older people report being happier. They describe having a greater satisfaction with life, and except for the “oldest old,” have lower rates of depression and anxiety.

How could this be? With age, your stress hormones are dysregulating with the fury of a 1930s furnace. Stress is supposed to be like oxygen to the rusting hull of your aging brain. Yet seniors just don’t seem to feel it. To understand why, we’ll need to explore more deeply the biochemistry behind stress responses, weird-sounding brain regions like the hippocampus and entorhinal cortex, mid-abdomen organs like our adrenal-capped kidneys, and thermostats.

Actually, we’re mostly going to talk about thermostats.

Running from the grizzly

Stress responses have one delightful job description: to keep you alive long enough to have sex. Your body has organized all kinds of hormones and cells and neurons into complex, interlocking sets of biochemical feedback systems in pursuit of this long-term Darwinian goal.

Though human stress responses are complicated, there is something simple you can say about them: when you’re stressed, your body dumps a ton of hormones into your bloodstream. Epinephrine and norepinephrine (or, if you are from the United Kingdom, adrenalin and noradrenalin) are often the first responders. Wielding immense physiological power, these catecholamine twins stimulate your cardiovascular physiology, increasing your heart rate, altering your blood pressure, and overstuffing your muscles with oxygen. They prepare your body to run away from Mama Grizzly.

This takes a lot of energy, of course, so your body recruits another first responder, the steroidal hormone cortisol, to help control the response. Cortisol is secreted by the adrenal glands, those pyramid-shaped tissues lying atop your kidneys. The elevation of these hormones in your body signal that you are in the grips of a fight-or-flight response, though to be perfectly blunt, it’s mostly about flight. Even against a juvenile hyena, we were (and are) too physically weak to put up much of a battle, so we did a lot of running, making us the Pleistocene era’s biggest chickens.

Cortisol has an important brain region in its gunsights: the hippocampus. This sea-horse-shaped brain region is famous for being involved in learning. It has custodial rights over the formation of certain memories, such as that bears are real threats. But it’s also involved in keeping your stress responses from wearing out their welcome once Mama Bear waddles off to eat berries and not you. Specifically, the hippocampus is involved in ascertaining the first possible moment when it can turn off energy-burning cortisol secretion.

This is a classic negative feedback loop. Proteins called cortisol receptors, which stud the hippocampus like raisins in cinnamon bread, are the mediators. When cortisol is released into the bloodstream, some molecules rush up to the hippocampus and bind to those cortisol receptors, like a key to a lock. The hippocampus is now alerted to the threat situation and is ready with a wide variety of responses.

One of its most important responses is turning off the cortisol spigot, shutting down adrenal activity when the threat is removed. Like spoiled rock stars in a hotel room, stress hormones actually start damaging their host if they overstay their visit. That includes brain damage, by the way. Small wonder that one of the first questions the hippocampus asks when cortisol binds to its receptor is an unfriendly one: “When can I make you go away?”

If the hippocampus ever failed at this job, your cortisol levels would remain abnormally high long after there was no reason to keep them up. That, unfortunately, is exactly what begins to happen to cortisol levels when you age. The hippocampus loses the ability to turn off the hormone.

And that has all kinds of consequences—which is where a working knowledge of thermostats comes in.

Cranking it up

Because I live in Seattle, I am used to lots of moist coolness, even in our warmest month (August). This is the opposite of Houston, where some of my relatives live, which has lots of moist hotness, especially vicious in August. So you can imagine my stress when, at a summer speaking engagement in the Houston area, I found my hotel room’s thermostat busted. Or should I say, its sensors were busted. It acted as if an arctic air mass had permanently parked itself in my room, because it kept turning off the air conditioner, trying to heat the room. It was as hot as a freshly baked potato.

As you know, thermostats aren’t supposed to work that way. You set the desired temperature, then let the sensors work their magic. If it’s too hot, the sensors automatically tell the AC to kick in. If it’s too cold, the sensors let the heater take over. This feedback system usually involves tiny strips of metal and the element mercury—and, in my case, a repairman. The hotel immediately called a technician, who fixed the thermostat, and the arctic air soon returned. The device behaved itself for the rest of my visit.

Minus the metal strips and mercury, your stress system has very similar feedback behavior. It even has a set point, though it’s more dynamic than my hotel-room thermostat’s. Cortisol is normally high when you wake up—anticipating a breakfast filled with predators, perhaps?—and then, if everything is calm, it faithfully depletes throughout the day. It’s not a trivial change. On a calm day, there is an 85 percent decrease from morning until evening.

This dynamic system is built to handle only one particular type of stress: a short one. From an evolutionary perspective, that makes sense. The grizzly bear either ate you or you ran away, but it was all over in minutes. It’s a finely tuned response, but it’s finely tuned only in short bursts.

The problem with modern society is that you can be caught in stressful situations that last for years—say, a bad marriage or a bad job—the physiological equivalent of the grizzly bear moving in with you. I mentioned brain damage. Indeed, exposure to unrelenting long-term stress can lead to major depression and anxiety disorders, which are true collapses of multiple brain systems.

We can graph this idea in the shape of an inverted U. At first, stress responses elevate both physical and mental functioning, the left-hand side of the graph climbing upward, reaching peak performance as long as the stressor doesn’t hang around too long. If stress overstays its welcome, the optimization turns into damage and you begin to slide down the ugly right-hand slope of the curve. Even properly functioning stress responses, to normal short bursts of stress, become dysregulated.

There’s another way stress hangs around too long: you’re outliving a system that was never built to handle life past thirty. Stress dysregulation ends up being a normal part of the aging process—one that is measurable. There are three manifestations.

The first concerns rhythm. Somewhere around age forty, baseline cortisol levels begin to rise. They stop following that lovely morning-high/evening-low rhythm and instead start sloping upward as if skiing uphill. Your body begins to experience the type of damage that occurs whenever stress hormones are elevated. We’ll have more to say about that damage in a minute.

The second manifestation is that you don’t respond as rapidly—or as vigorously—to the presence of threats. Take your cardiovascular system’s reactions to the epinephrine twins. From heart rate to blood pressure, all respond with much less vigor to the “all hands on deck” alerts as you age. You still make as much of the hormones as ever. You just can’t respond the way you used to. To make matters worse, once the alert has been sounded and your body begins to obey, the system takes longer to rev up the engine.

Finally, you don’t calm down as readily once you’ve finished reacting. With age, stress hormones have a harder time returning to baseline after a threat. It’s as if the aging body says, “Now that you’ve spent all this effort getting your stress responses elevated, I’ll be darned if I’ll let them return to earth so soon!”

Do these sound like thermostat issues to you, as if elderly stress responses were acting like my recalcitrant hotel room AC? To explain why, I’ll take a scene from one of my family’s favorite holiday movies, A Christmas Story, which also stars a disobedient temperature-control system.

A dysfunctional damper

The scene opens with Old Man Parker roaring, “Aha, aha, it’s a clinkerrr!” He’s watching black fumes pour out of a basement grate and into his 1930s living room. “That blasted, stupid furnace! Dadgummit!” He marches down the stairs to do battle with an obviously rebellious heating system. “For cripe’s sake, open up that damper, will you?!” his disembodied voice yells from the bowels of urban Hades. “Who the hell turned it all the way down?! AGAIN?!”

As you probably know, a damper is simply a flap in the flue of a chimney. Open it, and the smoke from your roaring furnace gets sucked outside. Shut it tight (when the furnace is off), and the damper prevents cold air from coming into the house. Toggle it back and forth, and you control the amount of oxygen available to the fuel source, a crude human-powered thermostat. It’s not working in the movie, which is the source of Old Man Parker’s increasingly colorful vocabulary. He eventually fixes it, and his profanity is the main price the family has to pay for thermal comfort. The voiceover cheerfully intones, “In the heat of battle, my father wove a tapestry of obscenity that, as far as we know, is still hanging in space over Lake Michigan.” Funny scene. Illustrative, too. I’ll use it to discuss not only the stress behind the old man’s behavior but how his unreliable human-based thermostat explains what happens as he ages. First the bad news, then—I promise—some good news.

The bad news is that when hormones like cortisol remain in your bloodstream, it’s like black smoke pouring into your house. Everything is a potential target for damage. Research from many labs shows a single disturbing pattern: the diseases that excess cortisol causes in humans of any age are the same diseases that eventually afflict nearly every senior. These include diabetes, osteoporosis, and various cardiovascular diseases, including hypertension. Since cortisol naturally elevates in aging populations, many researchers believe there is a direct link. I’m one of them.

Cortisol can damage specific brain regions, too. One primary target for its wrath is our memory-mediating hippocampus. That’s unfortunate because of the region’s critical role in our survival. It was essential for our species to forge a relationship between stress and memory in the Serengeti: the ability to recall a stressor is also the ability to remember to avoid it. As long as the stress isn’t prolonged, the hippocampus learns very valuable lessons about survival and passes them on to you. Remember the upside slope of the U-shaped curve?

Under conditions of prolonged stress, whether from chronic situations or from living past thirty, everything changes, and the hippocampus begins living with a brewing sense of its own demise. Recall that the response is finely tuned only for stresses of short duration. When too much cortisol hangs around too long, it can actually whittle away at hippocampal tissue, causing the organ to atrophy. Some neurons die, meaning excess stress literally causes brain damage. Those neurons that don’t expire can lose their ability to connect to one another. Some fail to respond to external signals, and the most alarming failure is the one I’ve mentioned: the hippocampus increasingly loses the ability to turn off your lifesaving cortisol elevations after the threat has gone away. The thermostat is becoming unresponsive as a direct result of cortisol overexposure. The net result? More cortisol overexposure, meaning more damage, which means more cortisol . . . you get the picture. As you age, your brain can turn into the dysfunctional furnace of A Christmas Story. This is the downside slope of the U-shaped curve.

How might this show up? You might find yourself more irritable. You might start to lose interest in things, or have unusual bouts of memory loss. Or you might not feel a thing. I wish I could give you clear signs to tell whether you’re under the kind of stress that causes brain damag...

Table of contents

• Cover
• About the Author
• Title Page
• Copyright
• Dedication
• Contents
• Introduction
• Social Brain
• Thinking Brain
• Body and Brain
• Future Brain
• Acknowledgments
• Index