How Do We Know That We Have A Cognitive Reserve?

By Sherrie All, Ph.D.

The theory of cognitive reserve was developed about 10 years ago after studying the brains of older people after they died and by studying people with brain injuries.

Over the years, brain researchers have come to understand that no two brains are alike.  Two people can experience the very same injury or stroke and have very different reactions.  It turns out that the main thing that distinguishes these people from one another is the amount of brain tissue that is "left over" after the injury and how that tissue is used.  If you have more brainpower in reserve, depletions are less costly.

In one important study, the brains of two groups of older people were examined. The people in one group showed the clinical symptoms of Alzheimer's disease when they were alive, and people in the other group had no signs of dementia. When the volunteers' brains were examined during autopsy, scientists discovered that there was no difference in the amount of Alzheimer's pathology (beta-amaloyd plaques and neurofibulary tangles) between the two groups.  This meant that there were people in the study who "had Alzheimer's in their brain" but never showed signs of the disease!  So in essence, the amount of Alzheimer's pathology that had grown had little impact on how the people functioned when they were alive.

Scientists were puzzled by this and wondered if there might be something different about the people in the two groups. When scientists went back and studied the lifestyles of the people in the two groups, they found that the people who did not have memory loss differed in several key lifestyle areas.  They were more educated, had more social relationships, and were more mentally active throughout their lives.  This was important because it showed that malleable lifestyle patterns that nearly anyone can adopt played an important role in who lost independence and who did not.  

What scientists have since concluded is that the more cognitive reserve you can build up, the more you can resist dementia, including Alzheimer's disease. 

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