you can reduce your risk for Alzheimer's by up to 50%

If you exercise the right way, you can reduce your risk for Alzheimer's by up to 50%
We have known for a long time that exercise helps keep our bodies fit. Now: More and more evidence shows that exercise also promotes brain fitness. For example, a study recently published in Archives of Neurology
showed that moderate-intensity exercise reduced the odds of developing
mild cognitive impairment, which often precedes Alzheimer’s disease, by
30% to 40% in the 1,324 study participants (median age 80).
But what type of exercise does the best job of strengthening the brain, and how much is needed for optimal effect?
What you need to know...
THE AGING BRAIN
After age 40, we lose about 5% of our brain cells (neurons) per
decade -- a process that often accelerates in those who are age 70 and
older.
Since the average person has hundreds of billions of neurons, his/her cognitive
reserves -- that is, the brain’s healthy cells that help compensate for
damage by recruiting other brain areas to assist with tasks -- may be
sufficient to maintain mental agility... but not always.
The risk: Millions of Americans who are
middle-aged and older start to "slip" in their mental capacities. Even
if they have no signs of dementia, it may be harder for them to remember
words, names or people than it once was. Or they may struggle to learn
new information or take longer to think through problems and find
solutions.
Why does this gradual mental decline affect some people much more than others?
Age-related loss of neurons, which affects all of us as we grow older, is just one factor. There’s also a decline in dopamine,
a neurotransmitter that controls motivation and motor function. This
decline interferes with the electrical signals in the brain that allow
the remaining neurons to communicate, which is necessary for memory,
speech and other key brain functions.
STRONGER BODY, BIGGER BRAIN
Scientists now know that the brain has plasticity, the
ability to form new neurons and connections between neurons. This
process can increase the brain’s ability to take in information, process
it and remember it.
What few people realize: Researchers have now identified a molecule -- brain-derived neurotrophic factor
(BDNF) -- that’s largely responsible for plasticity, and its levels
increase dramatically with exercise. In animal studies at the University
of California, Irvine, mice that exercised regularly were found to have
BDNF levels that were about four times higher than those in sedentary
mice. Many researchers think that humans show a similar increase.
The BDNF molecule could explain, in part, why people who exercise
tend to have less memory loss, are less prone to anxiety and depression,
and have up to a 50% lower risk of developing Alzheimer’s disease or
other forms of dementia than those who are sedentary.
Best exercises for the brain...
THE AEROBIC FORMULA
For overall fitness, the Centers for Disease Control and Prevention
recommends doing some form of aerobic exercise, such as walking, for 30
minutes at least five days a week. But that’s not enough for brain fitness.
Walking at an easy pace might increase your heart rate to about 50%
of its maximum. But this has little effect on the brain. For optimal
brain benefits, you need to exercise hard enough so that your heart is
pumping at 70% to 75% of its maximum rate.* Many treadmills have
built-in heart-rate monitors, and heart-rate monitors that you wear are
available at most pharmacies.
Good brands of heart-rate monitors: Garmin, Polar and Timex.
Important finding: One study published in Archives of Neurology
found that people who walked or jogged on a treadmill for 35 minutes at
a moderate intensity had improvements in cognitive flexibility (the
ability to think flexibly and creatively, rather than merely repeating
information) after just one session.
My advice: Exercise at a moderate intensity for 45 minutes to an hour, six days a week.
Remember, a moderate-intensity aerobic workout means elevating your
heart rate to 70% to 75% of its maximum capacity. At this rate, you will
most likely break a sweat and/or have difficulty carrying on a
conversation. You can achieve this by jogging, bicycling, swimming or
walking briskly -- and then pushing yourself harder when the exercise
starts to feel easy.
Example: Once you’re comfortable walking
for 45 minutes to an hour at the pace described above, increase the
intensity by walking faster, swinging your arms or holding hand weights.
If a moderate intensity is too much for you, exercising at 60% of
your maximum heart rate has also been shown to offer some improvement in
cognitive health.
cross training
To add variety to your aerobic exercise regimen, try some form of
cross training. It combines different forms of exercise to target
various parts of the body. Circuit training, in which you move quickly
from one exercise machine to the next without pausing, is one form of
cross training. Another is swimming followed by fast walking.
Cross training is useful because it generally results in a prolonged
elevation in heart rate, the critical factor for generating BDNF. Cross
training is desirable because it challenges not only your aerobic
capacity and strength but also calls upon parts of the brain that govern
coordination, planning, etc.
My advice: Whenever possible, incorporate
some form of cross training into your regular workouts. In addition,
balance exercises are a good way to round out your regimen. Try to work
balance exercises, such as tai chi or even any fast-paced form of
dancing, into your schedule once or twice a week. These exercises are
especially good because they increase your heart rate and require you to
think about what you’re doing.
Bonus: The social interaction that occurs in tai chi or dance classes and other group activities increases serotonin, a neurotransmitter that reduces anxiety and depression, both of which can impair cognitive functions.
THE POWER OF MOOD WORKOUTS
Research shows that the hippocampus (the brain’s memory
center) is 15% smaller in depressed individuals than in those without
depression. Exercise may be one of the most effective ways to reverse
depression -- perhaps because it influences the same neurochemicals that
are affected by antidepressants.
My advice: If you suffer from depression,
be sure to follow the exercise guidelines described above. This may
allow you to reduce or even eliminate antidepressant medication.
DON’T FORGET MENTAL WORKOUTS
Many different studies have shown that higher levels of education are
associated with a decreased risk for dementia. But it doesn’t matter
where you went to school -- or even if you went to school. The key
factor is continued learning.
Like physical activity, mental workouts increase the number of
connections between neurons that enhance memory and cognitive functions.
Perform mental workouts as often as possible. Good choices:
Try vocabulary quizzes, read books on subject matters you’re not already
familiar with or do any activity that requires you to push yourself
intellectually.
*To calculate your maximum heart rate, subtract your
age from 220. The goal is to exercise at an intensity that raises your
pulse to 70% to 75% of your maximum heart rate. The average 65-year-old
man, for example, will need to raise his heart rate to about 108 to 116
beats per minute.

Bottom Line/Health
interviewed John J. Ratey, MD, an associate clinical professor of
psychiatry at Harvard Medical School and a psychiatrist at the Beth
Israel-Deaconess Massachusetts Mental Health Center, both in Boston. An
adjunct professor at the National Taiwan Sports University, he is the
author, with Eric Hagerman, of Spark: The Revolutionary New Science of Exercise and the Brain (Little, Brown). His Web site is www.SparkingLife.org.