Secret Life of the Grown-Up Brain (16 page)

But Dr. Katzman also found something else. In what he called Group A, there were some patients who did not fit the pattern at all. The ten people in this group all had brains full of tangles. But, as was discovered later with people like Sister Bernadette and the Chess Player, they also had been functioning at a high cognitive level up until the very end. Lots of tangles, but mentally first-rate.

In the New York nursing home, Dr. Katzman had found the first documented set of escapees.

When I spoke with Dr. Katzman he was eighty-two years old and long retired, a professor emeritus of neuroscience at the University of California at San Diego. Still mentally alert, he easily recalled his reaction to his own escapee finding. “It was a surprise; we only set out to replicate the other studies,” he said. “And then we found this. It was new, very new.” (Dr. Katzman died in September 2008.)

As he wrote in February 1988:

Knowing that most new and unconventional ideas do not always find the warmest of receptions, I asked Dr. Katzman if he recalled the response of other scientists at the time. “Was it controversial? Oh, yes,” he said, laughing. “I mean, it was new, so automatically it was controversial. But I know I believed it then and I believe it now,” he added bluntly. “We had the data.”

As it happened, he also had something more. Katzman found that the Group A brains were not only somehow protected but also bigger. As he wrote at the time:

Wondering what it all might mean, he went on:

With that, the idea of cognitive reserve was officially born. It was also linked, from the start, to bigger brains. Indeed, a few years later, similar observations were made by a technician helping to dissect Sister Bernadette’s brain: “Look at the initial MRI scan,” the technician said. “It shows an unusual amount of gray matter.” As Dr. Snowdon elaborated in his book: “As it turns out Sister Bernadette had more gray matter . . . than 90 percent of the other sisters studied.”

So it’s possible to be an escapee, to both have tangled brains and still teach a class of ninth graders? But to do that, do you also have to have a giant brain? For those of us with smallish heads, this is a less than happy thought.

Luckily, science didn’t stop there. As the research into cognitive reserve has matured, it has become increasingly (and happily) apparent that there is more to all this than buff and brawn. While there is a correlation between brain size and reserve, cognitive reserve turns out to be much more complex—and possibly within reach—than that.

Indeed, one of the most prominent producers of this extra brainpower turns out to be something that would make your first-grade teacher proud: education. Just as those with more education seem to be better able to call on more parts of their brains when needed, education also seems to offer a kind of overall protection, at least against the outward manifestations of disease.

“Education changes the brain; that is now clear,” said Dr. Katzman when I spoke with him about where we are now with cognitive reserve. “I don’t think we know exactly how, but it changes the brain.”

In recent years, studies have found an indelible line between education levels, or, in the case of those with no access to formal education, literacy levels—and how well the brain ages. This is not a thought that comes completely out of the blue. For many years, education has been tied to living longer in general. The reasons are still being debated, but the idea remains steadfast and serious. As my colleague Gina Kolata wrote in a newspaper series on aging recently, “The one social factor that researchers agree is consistently linked to longer lives in every country where it has been studied is education. It is more important than race; it obliterates any effects of income,” adding that education may “somehow teach people to delay gratification,” a habit that might mean you giving up that cookie or cigarette and instead taking a walk.

Still, tying education levels specifically to brain aging has been more controversial and much more complicated. Some of the initial evidence came from the Nun Study, whose first results showed that those who had higher education levels aged more independently, and were able to bathe, eat, and dress themselves considerably longer than their counterparts with less education.

That tantalizing finding was small, however, and even David Snowdon of the Nun Study concedes that when he presented it at a scientific conference in 1988 the reaction was far from overwhelming, saying he’d had “a better audience for my 4-H project on chickens at the San Bernardino County Fair.”

Then Katzman found it, too. In one of the first large epidemiological studies in China, among five thousand people living in Shanghai in the late 1980s, Katzman found that those with no education had twice the risk of developing dementia than those who had attended middle school or even elementary school. Similar results were later found in population surveys of dementia rates in France, Italy, Sweden, and Israel.

“Alzheimer’s disease is a democratic process,” Katzman wrote, summing up his findings later. “Physicians and psychologists, chess masters and physicists, mathematicians and musicians may become victims of this disorder. . . . Yet a number of recent community studies report that individuals with a lack of education or low education are more likely to develop dementia and Alzheimer’s (AD). This . . . has profound social and biological as well as medical implications.”

Despite such findings, however, cognitive reserve has been battling an uphill fight for respectability. Doubts and disagreements persist. No one has suggested—or ever found—that education in any way prevents you from getting plaques and tangles or becoming demented. Going to school or becoming self-educated does not eliminate pathology. But beyond that idea, there has been consensus on little else.

And the whole concept, from the start, has had a serious chicken-and-egg problem. Was it simply that those with better brains sought more education or read more and then developed even bigger and better brains as a result? Were those who were inclined to become more educated simply the people who had better nutrition while young or had lives that were generally more protected from toxins that could harm the brain?

Many did not swallow the idea of brain reserve at all. One of these people was Yaakov Stern, a neuroscientist at Columbia College of Physicians and Surgeons. Fresh out of graduate school and working in Manhattan in the late 1980s, Stern had heard stories about cognitive reserve, or backup brainpower, an idea, he says, that was “being bandied about.” But he, like many others at the time, thought it was simply a matter of diagnosis. He believed that those who were more educated were simply better at doing the cognitive tests and were, therefore, less likely to be diagnosed as demented. “I thought it was diagnosis bias,” Stern told me.

As his career progressed, Stern found himself with a good position and adequate funding and he decided to take a serious look at the idea of cognitive reserve.

Interestingly, he, too, focused on a group of elderly living in Manhattan. His group was not living in nursing homes, however, and had a wide range of education levels, varied occupations, and was ethnically diverse as well. Because of his concerns about diagnosis, Stern was as careful as he could be to make sure that although the participants had varying levels of education, they were nevertheless at the same level of cognitive abilities when the study began. He also screened for signs of tiny strokes or vascular problems. Then he followed the group for four years to see what would happen.

And there it was again. Stern and his colleagues found that the better educated in the group were much less likely to show outward signs of dementia. To add a new wrinkle, he also found that those with more complex occupations, which usually meant dealing with human beings rather than working with repetitive machines such as on an assembly line, were also much less likely to become demented. In 1994, he published his study in the prominent
Journal of the American Medical Association.

“We found that those with less than eight years of education were twice as likely to become demented and those who had lower education and lower-level occupations were three times as likely,” Stern said.

The finding was, again, surprising, in particular to the skeptical Stern. What was important was that in this study all the participants were at the same place to begin with in terms of mental abilities and general health. The only way they differed was in their level of education. It was also important because it followed the group going forward, with no idea what the outcome would be. Indeed, the results were so striking that Stern went full-tilt to the other side and is now a true champion of the idea of cognitive reserve.

To fully convince himself, though, Stern set out to examine this reserve from every angle he could think of. He and his colleagues found that among those with the same outward signs of dementia, those who were better educated also had the lowest levels of cerebral blood flow, a sign of a higher level of pathology. In other words, again, the more highly educated had a worse physical condition inside their brains, but something was shielding them from the full force of their dementia. Like the nun and the Chess Player, something was helping them tolerate the would-be effects of the disease better.

In two other revealing studies, Stern and his team found that demented patients who had higher levels of education or occupation declined and died faster after being diagnosed. While on the surface that seems counterintuitive, it fits perfectly with the theory of cognitive reserve. It suggests that those who can call on more brainpower can hold back the outward signs of the disease. Then, by the time the disease becomes outwardly evident, its effects are much further along in the brain and those patients both get worse and die faster. These people, more escapees, as Stern says, “have less time to live with the effects of the disease and that seems like a good thing.” Better to be an eighty-four-year-old woman who has had no apparent problems and declines quickly and dies than one who spends years with feeble abilities.

Still, many researchers remained unconvinced and confused. After his first study was published, Stern got a call from a woman whose husband, a Nobel Prize winner, was suffering from a terrible case of Alzheimer’s. “She said, ‘What the hell are you talking about,’ ” said Stern.

Even though no one was suggesting—or says now—that education guarantees protection from dementia, the idea that something as amorphous as education could buffer the brain from the actual physical assault of a serious illness was a hard sell.

“We just didn’t think the brain worked that way,” said Stern.

But increasingly, it seems it does. Other solid studies, such as the Rush Religious Orders Study (more nuns, as well as priests) in 2004, also revealed that for a given level of severity, the more educated, on autopsy, had more tangles and plaques. Again, this suggested that those who had more education were protected longer from the most severe impact of the disease.

That same group found, too, that it was not just the level of education that was connected to the risk of dementia but also “cognitive-stimulating activities.” In a landmark study that helped boost the crossword puzzle industry, the Rush group found that over a five-year period, those who had done more to activate their neurons were about half as likely to develop Alzheimer’s. Stimulating activities were defined as those in which “seeking or processing information” was central and something you could do by yourself (to factor out the impact on socialization, which can also be hugely beneficial to the brain). That meant playing bridge was out, but reading magazines or newspapers, going to the library, doing word games, taking music lessons, or learning a foreign language were all counted.

A researcher in Stern’s lab at Columbia also added more solid evidence. In a study of 1,772 nondemented adults, Nick Scarmeas found that even those with a higher level of “leisure activities,” including walking, visiting with friends, or reading, had a 38 percent lower risk of developing dementia than those who did those things less often. And the risk of dementia decreased by 12 percent for
each
additional activity added, a finding that held up no matter what level of occupation or education.

Of course, it’s still very much possible that those who fill their lives with concerts and Chinese lessons might simply be better off, brain-wise, to begin with. But the most rigorous studies have done all they can to ensure that all participants are at the same general cognitive level from the start. It’s true, too, that some who do poorly may have early, undetectable stirrings of dementia or vascular disease. But as Stern’s colleague Nick Scarmeas sums up in a book on the latest research on cognitive reserve, edited by Stern: “Overall, the accumulated data seem to make a case for a protective effect of physical, intellectual and social activities for cognitive decline and dementia.”