Why do women with college degrees live several years longer and retain better mental and physical abilities after age seventy-five than their less educated sisters? Why is Alzheimer’s more apt to strike those who are less educated?
Its true that the better educated you are, the less likely you are to experience memory deterioration and dementia as you age. At first glance, this may seem extremely odd or more likely an indication that higher socioeconomic status or early avoidance of poverty and malnutrition convey special favors to the brain. Certainly, malnutrition influences brain functioning and, undeniably, genetics help define your upper limits of brain development.
But actually, nature’s design is more egalitarian. Whether your brain emerges relatively unscathed in middle and old age depends much more on your own mental efforts than you may have imagined. The idea is that exerting your brain intellectually, starting in childhood, spurs brain cells to explode with new branches, creating millions of new connections, or synapses, between neurons.
This means con-sistent mental stimulation actually builds more brain tissue, giving you a “bigger memory board,” so you can think more quickly. It also means that you have built up a bigger surplus of brain cells to call on, should your brain run into trouble with a stroke, brain injury, or degenerative brain disease such as Alzheimer’s.
Dr. David Snowdon, at the University of Kentucky’s Sanders-Brown Center on Aging, heads a long-range study of elderly nuns who donated their brains after death for autopsy. Dr. Snowdon suspects, among other things, that the most highly educated nuns, signifying brain stimulation, have a larger cortex with more branches and connections. This, he believes, enables them to withstand even Alzheimer’s disease with less evidence of mental devastation. “Nuns with the highest educational and intellectual life suffer least from symptoms of Alzheimer’s,” says Dr. Snowdon.
Unquestionably, scientists find a startling difference in the brain cells of laboratory rats raised in a stimulating environment. The neurons of stimulated rats are studded with extensive, long, and complex branches of dendrites; unstimulated rats have neurons with pathetically few short straggles of hairlike dendrites.
Arnold Scheibel, director of the Brain Research Institute at UCLA, credits evolution. He says the brain literally thrives on novelty in order to survive. The brain stem has an area called the reticular formation. Its wired to respond selectively to the new and exotic. This was a survival mechanism when we were on the lookout for predators. Now, new challenges activate your reticular formation and stimulate the growth of dendrites. That’s why people should not only remain active, but take up new pursuits.”
In a word, if you have more brain matter in reserve, from a lifetime of using your brain, you are apt to decline intellectually at a far later age than someone who did not vigorously exercise his or her brain. As experts analogize, the brain is like a muscle—using it makes it grow and expand; disuse causes it to atrophy. Thus, education makes brains more resistant to deterioration and disease, because people who earn degrees tend to exercise their brains more, building a more lively, resilient, and complex brain.
“Learning switches on genes in nerve cells which in turn stimulates growth of dendrites and synapses.” —William T. Greenough, University of Illinois at Urbana-Champaign
Having more synapses, dendrites, and neurons also may slow brain impairment as you get older. The more of them you have, the more you must lose before you see signs of failing memory and other mental functions as you age. For example, much research shows that the more severe the dementia in Alzheimer’s, the fewer the number of synapses between cells in the cerebral cortex, says brain researcher Robert Katzman, M.D., of the University of California, San Diego, School of Medicine.
He also finds that people with more education are less likely to develop Alzheimer’s, possibly because they use their brains more, keeping cells in shape. He conducted an epidemiological study in China, showing that less educated Chinese are four times more likely to die from dementias than better educated Chinese.
Dr. Katzman suggests that getting more education may delay the onset of Alzheimer’s symptoms by about five years.
Neurologist John Stirling Meyer and colleagues at Baylor College of Medicine in Houston studied 94 healthy people over age sixty-five for four years. Roughly one-third of the participants still had jobs; another third, although retired, stayed active mentally and physically, and the remaining third were relatively inactive.
Subjects were given standard IQ and other neurological and psychological tests at the beginning of the study and at the end. At the start, everyone had normal scores on the tests. After four years, the inactive group scored lower on IQ tests and on tests measuring blood flow to their brains.