Findings from Nun Study Show Contradictions of Alzheimer's Disease

Talk about an intriguing and very confusing puzzle! Does the exhibition of symptoms of Alzheimer's disease mean that a person actually has a tangle-filled brain? And what does the brain of a person who is mentally sharp when he or she dies look like?

Prior to her death. Recently, I had the opportunity to hear Dr. David Snowdon, the author of "Aging with Grace: What the Nun Study Teaches Us About Leading Longer, Healthier and More Meaningful Lives," during an Alzheimer's Symposium held at Texas A&M University. Dr. David Snowdon shared an interesting finding from brain autopsies (which provide significant data for this study) - the quantity of brain tangles indicating Alzheimer's disease could actually be the polar opposite to the mental abilities shown by the nun before her death.

"Most of the brains neatly fit our expectations, with little or no evidence of disease in a tack-sharp sister and abundant damage seen in a sister who had dementia," Dr. Snowdon wrote in the book. "But sometimes (Dr. Bill) Markesbery (the neurologist who did the autopsies) finds little evidence of Alzheimer's in a sister who had the classic symptoms of the disease. And sometimes brains from other sisters who appeared mentally intact when alive show extensive evidence of the disease."

This surprising information wasn't a set-up by the researchers.  In fact, Dr. Snowdon noted that Dr. Markesbery was not informed prior to conducting the autopsy about the mental status of that particular sister. After the autopsy, Dr. Markesbery met with Dr. Snowdon and the study's neuropsychologist, Dr. Kathryn Riley, to compare notes.

In one case - that of Sister Maria - Dr. Markesbery found that the nun had some plaques and tangles, but the number was not large. The nun's brain itself weighed within the normal range (most Alzheimer's brains have lower weights). Furthermore, the sister's brain rated Stage II on the Braak scale. (The Braak scale defines six distinct stages of the disease based on an autopsy. Stage 0 indicates the general absence of tangles. Stages 1-VI described the increasing range of the number and spread of the tangles throughout the brain.)

Following Dr. Markesbery's report, Dr. Riley shared Sister Maria's scores on three evaluations conducted prior to her death. These evaluations showed that Sister Maria had suffered progressive loss of her mental, physical and social functions in a way that was consistent with Alzheimer's disease.

Yet the reverse can happen as well. For instance, Dr. Markesbery's autopsy of Sister Bernadette's brain yielded the findings that she had Braak Stage VI, which indicates the most severe presence of Alzheimer's. However, Dr. Riley's report on the cognitive evaluations conducted in the years prior to Sister Bernadette's death showed that the nun was mentally sharp