Sister Mary was 101 years old when she died. Subjectively and from objective measures she showed virtually no mental decline. An autopsy showed that her brain was riddled with the plaques and tangles associated with advanced Alzheimer’s Disease.

It was in 1986 that an epidemiologist called David Snowden decided to study the evolution of dementia in older people. He wanted to create a group that he could study over a long period of time leading up to their deaths. The problem was older people have had very variable lives. A group of 75-year-olds bring to the study a multitude of experiences. Each could have a potential impact on the appearance and intensity of dementia.

He needed a group who had lived identical lives. He found them in 678 sisters of the School Sisters of Notre Dame. They had all joined the sisterhood in their early twenties. They had taught in catholic schools and retired to a motherhouse. Their lives might not be identical. But they had lived for half a century in the same routine and environment. At the time they were all older than 75.

The sisters agreed to be tested every year. Their mental ability was measured in multiple ways. They were classified according to their level of mental decline. Dementia was to be tracked from mild cognitive impairment through to Alzheimer’s. They provided background information on themselves. Uniquely he asked for something more. They agreed to donate their brains to science.

The Nun Studies.

The sisters were tracked for the rest of their lives. Their brains are still being investigated. They provided information for multiple studies. Many of the findings mirror studies described in previous Newsletters. The onset of dementia depended on the number of years of education. Just like last week’s Newsletter #238 "Dementia Starts at School. Higher education protected them from dementia.

In the filing cabinets of the convents, they found the “personnel files” of each nun. When they first joined the order, they were asked to write an autobiographical note. It was to describe their prior life. The researchers did not look at the content but the style. They were able to categorize each sister based on the complexity of the words and grammar they used. They assessed the sophistication of the ideas used in those statements. They could also categorize how positive each nun was about life. Both in general and about joining the order. They found that using this information from a 20-year novice could predict dementia symptoms 60 to 70 years later with 90% accuracy.

The complexity of the grammar used predicted dementia symptoms. The more descriptive the language the less likely dementia symptoms would appear. The more ideas that the nun packed into her autobiography the less chance that she would develop Alzheimer’s. The nuns illustrated the impact of positive attitude and longevity. The more positive those early world views the longer the nun lived.

Cognitive Reserve

The availability of the brains donated by the nuns was a first. It allowed researchers to look at the physical brain condition and mental ability for the same individual. Sister Mary was not unique. This was one of the most influential findings from the study. The relationship between the physical state of the brain and cognitive ability was not as strong as everyone expected. Other studies have confirmed this. They found 30% of people with physical symptoms whose minds operate normally. For researchers looking for cures, this was a problem and an opportunity. Was there something else going on? Did the physical damage not cause dementia and Alzheimer’s? Did the 30% of outlyers offer a different route to finding a treatment?

There are many explanations being suggested. Studies using scans have shown that older brains are still “plastic”. An older brain can still recruit novel parts to help solve a problem. Watching young and old brains solve the same problem shows that different parts are used. Does the early development of the brain help create plasticity?

The most prevalent theory is that some individuals have a cognitive reserve. Their brain is able to compensate for the physical impacts. It can sustain much higher levels of cognitive ability than expected. The autobiographical texts suggest that reserves can be built early in life. The connection between the physical characteristics of the brain and the mind still needs to be unraveled.