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 hippocampusa brain region crucial to learning
and memoryof 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
Dr. Albert's team identified three key factors consistently associated with
enduring cognitive function:
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 educationpossibly because they have a tendency
to read, travel, play word games, and participate in other
types of mentally challenging activities throughout life.
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.
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:
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 sleepgenerally
at least six hours per night.
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 harmand there may
be some benefitin 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.
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.
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
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
smoke. Smoking is highly detrimental to vascular health.
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.
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.
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.
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.,
From The Johns Hopkins Medical Letter: Health
After 50, August 2002.