Size Might Just Matter After All

We have known for some time that some persons do not manifest the clinical pathology of Alzheimer’s disease (AD) even though their brains have the hallmark plaques and tangles at autopsy. How this occurs is still not known, but one theory is that those persons who are able to fight the clinical aspects of the disease off may have more brain reserve, developed over the course of their lifetime. It is further thought that particular lifestyle factors such as exposure to enriched, novel and complex environments can help to build reserve.

A new study indicates that the size of the hippocampus, the structures that lie deep in the temporal lobe and help to form new memories and learning, may be important. Researchers at Oregon Health and Science University in Portland found that those persons who avoided dementia had larger hippocampi relative to those who did not avoid the manifestation of the disease. Both groups had the pathologic markers of AD.

Interestingly, the researchers did not find any difference in the two groups on education level or socioeconomic status. However, the study did not explore what the person did in their lifetime, the type of activities he or she pursued, or the quality of learning after graduation. While education level has correlated with reduction in the risk of dementia in other studies, the hippocampus may be stimulated by much more than formal education.

This is most likely the case given the research in 1998 that found the human hippocampus can generate new brain cells. Our goal should be to grow larger hippocampi through enriched environments across our lifetime as a health promoting behavior (see Dr. Nussbaum’s brain health lifestyle In this case, it is to potentially delay onset of dementia.

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