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Optimizing Those Brain Cells

Up until a few years ago, neuroscientists painted a dismal picture of the aging brain: Thousands of brain cells died every day, they said, year after year, decade after decade, eventually culminating in an enormous, inevitable cognitive deficit. Fortunately, this bleak view was misguided. Recent research shows that few neurons are lost and that, in reality, the brain is highly plastic, capable of reorganizing and rebuilding itself even into old age. Better yet, the evidence strongly suggests that certain good habits and simple lifestyle measures can preserve and even boost mental well-being, just as the risk of coronary heart disease may be lowered by exercise, diet, and proper treatment of risk factors like high cholesterol and hypertension.

Brain myths debunked

The human brain contains more than 100 billion nerve cells (neurons). Thus, even if thousands of them died each day, the lifetime toll would be negligible. But few are actually lost, according to Guy McKhann, M.D., Professor of Neurology and Neuroscience at Johns Hopkins and Director of the School of Medicine's Zanvyl Krieger Mind/Brain Institute. "Although there is some loss, it's far less than once believed and appears to be confined to certain highly select areas, with those areas essential for memory largely spared," Dr. McKhann says.

The long-held belief that neurons cannot regenerate also is inaccurate. In 1998, researchers proved that the adult brain contains cells capable of dividing and becoming healthy new neurons. Still more dramatic, these viable new cells were found in the hippocampus—a brain region crucial to learning and memory—of people as old as 72.

Instead of dying, neurons seem to shrink. Although this shrinkage appears to contribute to the general slowdown of mental function associated with aging, it does not seem to cause disability. Serious mental impairment seems to occur only when vast clusters of neurons are destroyed by a major disorder, such as stroke or Alzheimer disease (AD).

It also appears that a reduction in the production of neurotransmitters (specialized brain chemicals needed to conduct nerve signals from one neuron to another) contributes to age-related memory changes, which may be good news. "If the neurons themselves are still intact and only the neurotransmitters are lacking, we might be able to enhance the speed of mental processing by treating the chemical deficiency," Dr. McKhann says.

What these and other recent findings show is that the brain is not hardwired but remarkably plastic, even when challenged by stress. For example, in the wake of a stroke, the brain can often compensate for damage to speech or motor centers by rerouting nerve signals through new pathways.

Hallmarks of a healthy brain

In the early 1990s, a major research study sponsored by the MacArthur Foundation set out to determine why some people are blessed with lifelong mental sharpness. The study, published in the journal Psychology and Aging, looked at more than 1,000 people between the ages of 70 and 80. One of the scientists leading the project was Dr. McKhann's wife and colleague, Marilyn Albert, Ph.D., Professor of Psychiatry and Neurology at Harvard Medical School and Director of the Gerontology Research Unit at Massachusetts General Hospital.
Dr. Albert's team identified three key factors consistently associated with enduring cognitive function:

Education and mental activity. Repeated rehearsal of information and the development of critical thinking skills promote plasticity, increasing both the number and the strength of synapses (electrochemical connections between neurons). This finding may explain why people with college degrees consistently appear to be less vulnerable to memory loss and dementia than those with less formal education—possibly because they have a tendency to read, travel, play word games, and participate in other types of mentally challenging activities throughout life.

Physical activity. The brain requires more oxygen than any other organ. It utilizes about 25% of all the oxygen taken in by the lungs, yet it has no oxygen storage capability. Thus, brain cells need a continuous supply of oxygen-laden blood. Regular, vigorous aerobic exercise enhances circulatory health, which, in turn, promotes adequate oxygen delivery. Dr. Albert's research revealed a surprising new finding: Regular physical activity also boosts levels of naturally occurring trophic factors, proteins necessary for healthy brain function. Animal studies have likewise shown that exercise stimulates the growth and development of new brain cells in regions like the hippocampus.

Emotional well-being. Having a strong sense of purpose and meaning in one's life is another key characteristic of people who thrive in their later years. Frequent contact with family and friends, community activities, and satisfaction with one's accomplishments are all important. A sense of humor, religious or spiritual convictions, good general health (absence of chronic disease), and relative financial comfort are helpful as well.

What you can do

In addition to keeping your mind sharp through mental stimulation, physical exercise, and social connections, several other measures can help optimize brain health:

Get adequate sleep. As we age, we need fewer hours of sleep per night and tend to awaken more frequently throughout the night. It is nonetheless crucial to get enough sleep—generally at least six hours per night.

Eat right. Although there is no compelling evidence that any foods or nutrients will enhance normal memory or intelligence, a well-balanced, low-fat diet is essential for good circulatory health. Most people get enough vitamins through their diet alone, although there is probably no harm—and there may be some benefit—in taking a multivitamin. As for herbal supplements, there is some preliminary evidence that ginkgo biloba may slightly delay the progression of AD but no evidence that it protects against the general slowdown of mental processing that occurs with normal aging.

Women might consider hormone replacement therapy (HRT). Although studies have yielded conflicting results, some research indicates an association between HRT and decreased AD risk. It is believed that estrogen may promote the production of neurotransmitters and the growth of new neurons, as well as improve blood flow and glucose utilization in the brain. However, recent studies have linked HRT to an increase in heart attacks, strokes, breast cancer, and blood clots.

Manage stress. Stress triggers the release of cortisol and other hormones that can block the production of new brain cells and, over prolonged periods, kill neurons. Stress hormones can also lead to chronic medical conditions capable of undermining brain health. Regular exercise, yoga, meditation, and seeking help from support groups or a professional counselor can help defuse stress.

Limit alcohol and caffeine intake. Excessive alcohol consumption can quickly damage large numbers of brain cells, which can lead to confusion, impaired balance and coordination, sleep disturbances, and depression. While a little caffeine temporarily seems to enhance concentration, too much can cause jitters and confusion.

Don't smoke. Smoking is highly detrimental to vascular health.

Treat chronic physical and mental problems. Certain health problems can lead to secondary problems in cognitive functioning. For example, treatment of diabetes can produce hypoglycemia (low blood sugar), which starves the brain of the glucose it needs to function properly. Similarly, heart disease can reduce the brain's blood supply. Mental and emotional problems, such as depression, grief, and anxiety, can make it difficult to concentrate, learn, and remember.

Limit television. Watching television is not stimulating in the same constructive way as mentally engaging activities such as reading, conversation, and playing word games and puzzles.

Periodically review your medications. Cognitive problems can be a side effect of many prescription and over-the-counter drugs. Furthermore, some drugs that would be harmless when taken alone may cause problems when combined with other drugs.

Break with routine. Simple tricks like occasionally brushing your teeth with the nondominant hand, taking a different route on your errands, and finding your car keys by touch instead of sight can help sharpen mental skills.

For more information:
McKhann G, Albert M: Keep Your Brain Young, 2002 (John Wiley & Sons, Inc., New York)

From The Johns Hopkins Medical Letter: Health After 50, August 2002.


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