Many studies over the years have demonstrated that physical activities improve brain function.  Rats subjected to spinning and turning responded with a measurable increase in size of the part of the brain regulating balance.  My own experience with brain-injured  children over several decades, including those with autism, Down syndrome, cerebral palsy, traumatic injury, and others, revealed improvements in brain function directly corresponding to the amount of sensory, intellectual and physiological input, offered to the brain.

We have seen that individuals with dementia, when isolated and lacking human contact, recede into a vegetative state.  It is apparent that the brain grows through use, and withers when dormant.

A new study reveals the connection between fitness levels in mid-life and the incidence of dementia in the next 25 years. (Annals of Internal Medicine, 5 Feb 2013, pp 162-168)

There were 19,458 men and women, ranging in age from 45-50 years.  All had a treadmill stress test, with level of fitness determined by maximum time on the treadmill.

Subjects with the lowest level of fitness had the highest incidence of dementia after 25 years of follow-up, by which time all subjects were over 65 years of age.  There were 1659 cases of dementia.  Individuals with the highest level of physical fitness had a 35% reduced risk of dementia compared to those with the lowest exercise tolerance. This finding was independent of established cardiovascular risk factors, including history of stroke, high blood pressure, diabetes, cholesterol level, smoking and alcohol use.  Thus physical fitness by itself was a determinant of later-life dementia.

How to explain this?  Improved physical fitness protects against high blood pressure and diabetes.  Improved physical fitness is also associated with greater brain volume, which may enhance cognitive function.  Magnetic resonance angiograms (MRA) have shown an increase of small caliber vessels in the brain in exercising subjects, suggesting an increase in brain blood flow. One study in exercising mice revealed a decrease in amyloid, a protein found in degenerating brains, in the hippocampus and frontal cortex.  The hippocampus is involved in the formation of new memory, and the frontal cortex in judgment and cognitive processes.  

Fitness levels are modifiable through training.  Regular exercise for 2 1/2 hours a week for 5-6 months raises maximal oxygen consumption to permit a 1-2 MET increase in exercise capacity.  (One MET is the amount of energy generated at rest.  A person in good condition should be able to achieve 10 METS at maximal capacity.) 

The best way to improve fitness is to pursue activities you enjoy.  Unpleasant forms of exercise are unlikely to be maintained over time.  I swim 2/3 of a mile two or three times a week, ride my bike twelve miles once a week, partly up a very steep hill, and work out with stretching and light weights 5 days a week.  

Recently my wife introduced me to tango, her personal intensive exercise.  Dancing can thoroughly satisfy the exercise requirement, and is also good for your soul.  Many of my patients do tai-chi, Pilates, yoga, mountain climbing or hiking, surfing, tennis, or volleyball.  Some do intensive structured anaerobic workouts. If you have more variety you can do something every day.

A correlative finding of the exercise study was a reduced incidence of lung and colorectal cancer in men who were at the highest level of fitness.  Compared with men in the lowest quintile of fitness, those in the highest quintile had a 67% reduction in lung cancer and 33% reduction in colon cancer incidence.  

In another article (Mayo Clin Proc, Jan 2013, pp11-21), the level of prostate specific antigen (PSA) was found to be lower in men who exercised more.  A one-hour daily increase in light physical activity reduced the risk of having an elevated PSA by 18%. Exercise may effect a lower risk of developing prostate cancer, inflammation, or enlargement.  It may also reduce the risk of having to undergo painful diagnostic biopsies.

Exercise works to accelerate metabolism of toxic substances, enhance immune function, and reduce the stress known to aggravate any medical condition.  For all these reasons, and to help you feel better, utilize exercise as a core strategy for health.

We read about people who exist in the extremes of environment: natives high in the mountains of Peru and Nepal, where oxygen is scarce; bushmen in the Kalahari Desert, who rarely drink water; Eskimos in the Arctic, who can function in debilitating frigidity.  

Other forms of life have their own environmental challenges.  The July 2013 issue of the National Geographic offers a 2-page color-enhanced electron microscope photo of a most remarkable creature: the tardigrade.  Also called a water bear, it is half a millimeter long, with eight legs and a mouth that looks like a fire hose nozzle.

The tardigrade can exist in temperatures approaching absolute zero (-200 degrees Centigrade), and in heat above boiling (150 degrees Centigrade).  It can tolerate a pressure of 6,000 atmospheres, more than the deepest part of the Pacific Ocean.  It can be exposed, without dying, to 1000 times more radiation than a human being.  It can live for 10 years without water, while changing its body composition from 85% to 3% water.

The tardigrade is an exceptionally hardy animal.  It demonstrates that life has the capacity to survive. We humans, in our advanced position on the evolutionary line, also possess, innate to our existence, the urge to survive. That truth, however, may be obscured by adversity and disappointment, leading us to diminish our estimates of ability, and our hopes.

At times of stress, we should remind ourselves that we are more resilient and more durable than we realize.  I have seen many people emerge at the other end of physical and emotional catastrophe.  A 90 year-old man lingering on a ventilator for three months with respiratory failure from pneumonia, recovers to roll his walker across the street to his favorite store.  An 80 year-old woman with metastatic breast cancer endures surgery after surgery to remove tumors from her body, still married and still active after 20 years.  A boy with severe cerebral palsy grows up to become the sports writer he was told he would never be.

Like the tardigrade, but in our own way, we know how to survive.