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by Zaldy S. Tan M.D., MPH
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“If the brain were so simple we could understand it, we would be so simple we couldn’t.”
Welcome to the club. If you picked up this book, you probably are one of the millions of people around the world who is beginning to worry about his memory. Lapses in memory that become more frequent with the passage of time lead many of us to question why our memory isn’t as sharp as it used to be. How many names are we allowed to forget? How many times can we misplace our keys and glasses? And how many minutes should it take us to locate a parked car before we need to start worrying about the state of our minds?
When I was a twenty-two-year-old freshman in medical school, I spent many days sitting through series of hour-long lectures given by a succession of wise elderly doctors, their monotonous voices reverberating through the walls of the lecture hall. Although I never thought anything of it at that time, I now look back with fascination on my ability to accumulate a sizable wealth of technical knowledge within a relatively short span of time. Like a sponge, my brain absorbed enormous amounts of esoteric medical information. At the time, I suspected that I might never find any practical use for much of this information in my medical practice. But my brain held on to the data just the same. The fact that I can still remember things I learned many years ago is a testament to the remarkable efficiency of young brains to acquire, process, retain, and ultimately retrieve new information.
As we get older, it is not unusual to sense a subtle but perceptible dip in our ability to acquire and retain new information. For instance, it may take us a few seconds longer to process and retrieve certain types of information, such as our ATM number or the date of our next dental checkup. In an age when overlapping appointments and back-to-back meetings are the norm, many of us have become willing hostages to various forms of memory crutches. If you don’t believe me, just think of how you felt the last time you misplaced your date book or how disorganized your day was when your secretary called in sick. The popularity of Post-it notes, car dashboard computers that make irritating noises when you leave the key in the ignition, and the ubiquitous FORGOT YOUR PASSWORD? button on Web sites all help to keep our imperfect memories from interfering with the flow of our busy lives. With our generation’s increasing dependency on memory crutches now, have you ever wondered about the fate of your memory in the next ten or twenty years?
Many consider a sharp memory to be just one of the vestiges of youth that we should expect to part with sooner or later. This feels even truer for those who have been silent witnesses to the blunting of the memory of a forgetful parent or grandparent. But if memory problems and aging are truly inseparable and everyone is destined to become forgetful eventually, how can we explain the not-so-uncommon observation that many older people such as Georgia O’Keeffe, Winston Churchill, Golda Meir, George Burns, and Strom Thurmond somehow managed to remain mentally sharp well into their ninth and tenth decades?
DESTINED TO FORGET?
While we have learned to accept the reality that excellent physical health is fleeting, we all hope to at least be able to hold on to our memory and to take it with us when the time comes for us to make our exit. For many, a healthy mind trumps a healthy body anytime.
In reality, many of the diseases that we commonly consider as part of aging, whether these be arthritis, impotence, or Alzheimer’s, are not inevitable. For a disease to be truly unavoidable, it should be expected and observed to appear in everyone who reaches or goes beyond a certain age. Yet we know that among us are people who will be able to bake the cake to celebrate their hundredth birthday, while others will succumb to Alzheimer’s disease and not even remember their sixty-fifth.
Some scientists believe that in the absence of disease, we should all be able to maintain our mental abilities well into old age. Others think that memory decline is part and parcel of normal aging and that the rate of decline is the only thing that distinguishes the mind of the diseased from that of the normally aging. The truth is probably somewhere in between. While it is theoretically possible (with the combination of perfect genes, ideal environmental conditions, and a healthy dose of luck) to completely dodge the memory changes that typically accompany aging, most of us are likely to develop age-related changes in memory performance to a certain degree. These changes can be observed and measured by standard memory and psychological tests. However, this does not mean that everyone is destined to have noticeable changes in their memory during the course of their everyday lives. In this book, you will find tests designed to help you detect early signs of memory problems. I will also outline how relatively simple changes in your diet can help in warding off premature memory loss. The Sixty-Minute Brain Workout will provide you with mental exercises that can strengthen specific areas of brain weakness. The important thing to remember is that there are things you can do to tip the odds of memory preservation versus decline decidedly in your favor. You are not destined to become forgetful.
Arguably, no other part of our body is as unique or complex as our brains. Its strengths, weaknesses, thoughts, and experiences are so distinct that making absolute statements on what is normal and what is not is next to impossible. One of the biggest challenges in identifying people with abnormal memory loss is determining where to draw the line that will effectively distinguish the normal changes in memory that occur with aging from those that characterize very early Alzheimer’s disease. To appreciate the remarkable complexity and uniqueness of our brains, let’s take a step back and get better acquainted with the origins of this mysterious organ.
THE SIXTY-FIVE-MILLION-YEAR-OLD BRAIN
If I ask you to tell me your last cholesterol and blood pressure levels, you probably won’t have too much difficulty in coming up with the numbers. Many people routinely mark down the dates for their next mammogram, colonoscopy, Pap smear, or PSA with red ink in their calendars to emphasize the importance of these health screening procedures to the maintenance of their health. Yet if I ask you to tell me the status of your memory, you would probably scratch your head and tell me that you have no idea.
Have you ever wondered why, despite all the high-tech medical advances in our generation, we still cannot take a test that will tell us the state of our minds, much the way simple tests can tell us the state of other vital organs such as our hearts? From looking at a set of squiggly lines on a strip of paper, a cardiologist can immediately tell how well your heart is functioning. The electrocardiogram (EKG) is a quick, simple, and inexpensive piece of equipment found in many doctor’s offices that can detect an enlargement of the heart, spot irregularities in its rhythm, and even catch an evolving heart attack. Unfortunately, there is currently no equivalent test that can tell us how well the brain is functioning. Thus, the best way to get to know how well your mind is functioning is to periodically monitor the accuracy and efficiency by which you can tackle challenging intellectual tasks, such as those presented in the Memory Stress Test. But before you do that, you must first gain a better understanding of how your brain normally functions. Only by acquiring this basic knowledge will you understand what the different tests tell you about your mind. Recognizing how the brain normally functions will then allow you to recognize the first signs of problems when they appear.
For starters, the brain is a three-pound walnut-shaped mass inconspicuously hidden behind the bony skull. Compared with the heart, the brain is an infinitely more complex organ. Unlike the dynamic heart, which sits in the center of the body, ready to physically respond to the calls of joy and sadness, love and anger, valor and fear, the brain does its job quietly and efficiently, without much drama or fanfare. Thus, it is not too difficult to see why early civilizations quickly dismissed it as a nonessential organ that served no real purpose other than perhaps to fill space or cool the blood.
Of course, we now know that the brain is much more than the body’s equivalent of a car radiator. It is a sophisticated and powerful organ that is the product of millions of years of evolution, exerting control and dominance over the rest of the body. The origin of the modern human brain can be traced back to more than sixty-five million years in the past, roughly to the time when dinosaurs became extinct and mammals became free to roam the earth.
Compared with other mammals, members of the primate family, which includes monkeys, apes, and of course humans, have larger, heavier, and more complicated brains. The human species is believed to have evolved from land-dwelling chimpanzees over a period of only about one hundred thousand years. Considering the amount of intellectual evolution that must occur to allow us to surpass the abilities of our most intelligent cousins in the primate family, it took a relatively short span of time for the modern human brain to emerge. In fact, we still share 98 percent of our genetic codes with chimpanzees, and certain structures of the human brain have changed very little or not at all from its primate origin.
THE MASTER OF THE MIND
From its primitive past, one part of the brain has evolved so completely and effectively that it is credited with shooting the human species straight to the top of the evolutionary tree. The cerebral cortex is the most highly differentiated of all the areas of the human brain. The cortex, which literally translated means “rind” or “peel,” is the outermost layer of the brain. It is a relatively small structure, with an area of only approximately two thousand square centimeters (roughly equivalent to that of a car’s hubcap). But cramped in this small area are more than fifteen billion brain cells or neurons and an even greater number of supporting or glial cells, which nourish and protect the brain cells from damage. To communicate with each other, each neuron makes more than a thousand connections called synapses to others like it, forming an interweaving network that transmits vital information throughout the intellectual superhighway.
The cerebral cortex is the true center of human intelligence. It is also the prime target of degenerative diseases such as Alzheimer’s, which threaten to knock us down several notches from our comfortable perch high up on the evolutionary tree. Its peculiar vulnerability to disease can be explained by the exquisite sensitivity to damage of the brain cells that live there. As we age, an increasing number of these brain cells succumb to cumulative damage, with a resulting decrease in brain reserves. These changes make older people more susceptible to memory loss and decline in other mental abilities. Thus, prevention efforts against memory problems seek to protect the delicate brain cells of the cerebral cortex from harmful agents and degenerative diseases.
I should emphasize that the aging process itself will not cause you to develop Alzheimer’s disease. Brain aging is not a disease; rather, it is just a part of human development that begins at the moment of conception and ends at the time of death. Studies have shown that the ever-changing human brain continues to transform itself even in the late stages of life. However, at no time in the human life cycle is the brain more dynamic than during the first few years of life. In fact, the pattern of early brain development provides us with some valuable insights that will help us to better understand the mysteries of the aging brain.
THE AGING BODY AND BRAIN
When most people think of aging, stereotypical images such as gray hair, wrinkled skin, and a stooped posture readily come to mind. But beneath the skin’s surface, our internal organs also experience dramatic changes with age. During infancy and childhood, our various organ systems grow and mature. With the notable exception of the brain, they reach their functional peak during late adolescence and early adulthood. They then enter a plateau period that typically extends from early adulthood to middle age. It is during this reproductive period of life that organ systems are functioning at their optimal level.
By the time we reach middle age, our bodies have begun to show signs of wear and tear—and we feel it. The heart, kidneys, lungs, liver, and virtually all other organs go through such age-related changes. The kidneys, for instance, lose 20 to 30 percent of their weight between the ages of thirty and ninety years, and their length shortens by half a centimeter for each decade after age fifty. Though continuing to function normally, many of our internal organs become more vulnerable to disease. Physically active older people, such as former professional athletes, notice that even though they continue to exercise, their muscles still become smaller and less prominent compared with when they were younger. This is explained by the normal decrease in muscle mass with age that is largely independent of the level of a person’s physical activity. For the same intensity and frequency of exercise, the muscles of a sixty- or seventy-year-old simply cannot get as large and as strong as those of people in their early twenties.
The Shrinking Brain The maximum weight of the brain is attained at around age twenty and remains relatively stable until about age forty. But under the microscope, scientists have seen brain cells start to die as early as age thirty. Estimates show that by late middle age, we are losing an average of about 1 percent of our brain cells every year. In fact, between the ages of eighteen and ninety-five, the human brain is estimated to lose 57 percent of its brain cells. Because our skulls typically do not shrink with age, the lost brain tissue is replaced by fluid and dead space, leaving large, dark holes where healthy brain tissue used to be.
Parallel to the loss of muscle mass and strength, there is also a corresponding connection between brain volume and age. The brain of a young person looks like a complicated mass of wrinkled fat tissue, with numerous peaks (gyri) flanked on either side by valleys (sulci). As the brain ages, it changes physically: slowly losing its tall peaks and gaining wider valleys. The brain significantly shrinks and acquires a smoother surface. This age-related loss in brain mass occurs at an earlier age in women than men. Ironically, women begin to lose the wrinkles in their brains at an age when they notice the increasing appearance of wrinkles in their skin!
Fortunately, for every rule, there are exceptions. Many of us have personal stories of eighty- and ninety-year-old relatives and friends whose intellectual capacities do not seem to show any signs of age. Studies have confirmed that the brains of certain individuals do not lose a significant amount of volume. Instead, these brains resemble those of much younger people. This only goes to show that whether on the physical or mental level, the rules of brain aging can and are meant to be broken!
THE AGING OF THE MIND
If somebody stopped you on the street today and asked you to rate your memory, what would you say? Well, if you are a typical person over the age of fifty, you will probably say that it isn’t as good as you’d like it to be. Studies have shown that compared to young people, older adults have a greater tendency to rate their memory ability as poor; many of them believe that they forget things in their everyday lives more frequently and perceive their memory as declining rather than remaining stable or improving. Perhaps most significantly, many older adults see age-related memory decline as inevitable and not modifiable by practice and training.1 The perception that memory and other mental abilities plummet as chronological age rises stems from people’s interpretation of their personal episodes of memory lapses. The stereotypical portrayal of forgetful older people by the popular media also helps cultivate this belief.
Great Minds Don’t Necessarily Think Alike A statistical measure of variability demonstrated that compared with their forty-year-old counterparts, the mental test scores of seventy-year-old physicians had 60 percent more variability, and those of seventy-five-year-olds had greater than 100 percent more variability. In other words, as people get older, their mental abilities become less uniform. Rather than becoming more alike and uniformly senile, our minds actually become more different the older we get!
In reality, many people do not reach the pinnacle of knowledge and intellectual skills until relatively late in life. The minds of people who lead intellectually stimulating lives can even continue to grow and mature well into late adulthood and old age. But how then can we explain the observation of most middle-aged people that they are not able to learn and remember new things as swiftly as they did during their college years? The evolution of certain characteristics of the human mind as we age accounts for this phenomenon. The efficiency and speed by which we learn new information peak somewhere between the ages of twenty and thirty years, followed by a plateau period that typically extends several decades. Certainly, this does not mean that people in their thirties and forties cannot learn new concepts and skills; only that it may take them slightly longer to do so compared with when they were in their twenties. Fortunately, the wealth of life experiences, knowledge, and skills that we accumulate with age is more than enough to mitigate the very subtle decline in learning efficiency. In fact, a study of changes in mental speed with age showed that there were seventy-year-olds who surpassed the performance of some people in their twenties. This highlights the remarkable ability of the human mind to adapt to age-related changes by relying on mental skills acquired through experience.
THE HARVARD STUDY
A Harvard University study of more than a thousand aging physicians reported that between the ages of forty and seventy-five years, mental ability can be expected to decline by as much as 20 percent. Upon casual inspection, this appears to be rather disturbing, especially when taken together with other studies showing that average scores on memory tests decline steadily as early as after age twenty-five. But the mental declines with age observed in these highly educated professionals are not as apocalyptic as they may initially seem. The key word here is average. This means that while some people suffered a decline of 20 percent or greater, others had a much less precipitous drop in mental function and still others experienced no mental decline at all. If anything, the findings of this study helped shatter the widely held belief that mental capacities decline uniformly with age.
How can we explain the fact that at age seventy-five, some people are playing chess, balancing their checkbooks, and tending their gardens, while others cannot even find the nearest bathroom? This is the million-dollar question that we will answer in the rest of this book. One thing we know for sure: Not all people are destined to suffer a decline in mental capacity simply because of age. Clearly, other factors are at play separating those who are able to keep the mind young from those who begin losing it even before they reach middle age.
RAYS OF HOPE
Many scientific studies have shown that the minds of people age differently. By conscious effort or pure luck, some of us will choose the path that leads to successful brain aging, allowing us to keep our mental capacities intact indefinitely. But some of us might not be so lucky and instead choose the path that leads to memory loss. The clear message of the most recent scientific studies is this: Taking relatively simple steps has the potential of altering the destiny of the mind. If you were presented with the choice, which path would you choose?