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The Nun Study

Sister Mary of the School Sisters of Notre Dame lived to be 101 years old. In her final years, she showed remarkable cognitive ability, lightyears beyond that of most centenarians.

So, what was the secret to her longevity? Was it a miracle drug? Or a lifelong habit of rigorous exercise? According to Sister Mary’s doctor, the reason for her long, happy life and healthy mind was her positive attitude. That may seem like flimsy reasoning for a medical professional to assert, but it’s not as far-fetched as it may seem. 

In the 1980s and 90s, researchers from the Universities of Kentucky and Minnesota studied the cognitive health of 600 nuns like Sister Mary. The study involved several tests of mental health and habits throughout each sister’s life. It also ensured that the research team could examine the brain of each participant after her death.

The scientist who led the investigation sought to understand what factors played the most significant roles in determining late-life cognitive health and function, like preventing Alzheimer’s and dementia. Within a few years of the study’s commencement, the researchers found their answer and much, much more. 

It turned out that several simple indicators, like linguistic ability and positive emotions, were strongly correlated with late-life cognitive health. These characteristics allowed some women to maintain their memory and critical thinking skills despite Alzheimer’s impacting their brains.

But, the most impressive findings went beyond cognitive health. For example, by analyzing and comparing a 300-word writing sample from each woman’s early life, scientists could predict the likelihood that she would die in the next five years. Of course, it’s never quite that simple.

There are many important lessons that we can draw from the Nun Study. To understand them, we’ll have to delve deeper into the investigation’s nuances and the mysteries of the human mind.

Let’s explore.

Humankind’s understanding of dementia and Alzheimer’s is incredibly limited for a condition that could affect anyone late in life. More than 2,000 years ago, Greek and Roman physicians and philosophers first noted the cognitive decline in people who lived to be more than 50 or 60 years old. Yet, until the early 20th-century, Alzheimer’s disease had never been identified. 

In 1901, a German doctor named Alois Alzheimer followed the cognitive decline of a 50-year old patient named Auguste Deter. The doctor observed Deter until she died in 1906. Then, Alzheimer examined Deter’s brain, finding an abundance of senile plaques and neurofibrillary tangles. In other words, it wasn’t just that the brain was operating differently. It had undergone severe abnormal physical shifts, and those material changes had contributed to the patient’s deterioration.

Alois Alzheimer
Alois Alzheimer

Doctor Alzheimer’s name became associated with the degenerative brain disease that stems from complex brain changes. Thus Alzheimer’s disease—or AD—is the most common cause for dementia, a general term that describes the symptoms of cognitive decline like memory loss—in simple terms, dementia is a symptom of Alzheimer’s. 

Despite the disease’s identification, Alzheimer’s has confounded doctors for the last 120 years. It took the better part of a century for neurologists to identify risk factors and potential treatments. In large part, that lack of understanding stems from the lack of healthy brains for doctors to study. Then, in the 1980s, a professor of cognitive science named David Snowdon designed a groundbreaking study that would grant him access to hundreds of healthy brains and shed light on AD risk factors.

Snowdon had one fundamental question—what factors in early, mid, and late-life increase the risk of AD and other brain diseases? It was not an altogether unique question, but Snowdon differentiated his study by examining a distinctive group of subjects. 

The School Sisters of Notre Dame is a multi-state Roman Catholic organization in the US. The convent’s nuns dedicate their lives to education and service, making them enthusiastic participants in a study aimed at improving public health. But, the sisters were ideal subjects for two other reasons. 

First, SSND kept detailed archives of each sister’s writings. In the early 20th century, the convent required all its’ women to write a brief biographical paragraph about their early lives. This gave Snowdon first-hand information on his participants’ early lives, something impossible to get in most similar investigations. That’s because, for most Alzheimer’s studies, the only source of information on a participant’s early life is to interview the participant. But interviews are unreliable, particularly when the subject suffers from a degenerative cognitive disease and is answering questions about 60 years prior.

The second advantage was the ability to control for many variables. The nuns who participated were non-smokers, drank little alcohol, had the same marital status and reproductive history, lived in similar housing, held the same jobs, and had equal access to medical care. Their homogeneity offered the rare ability to remove many potential factors that obscure the results of other studies. 

In 1986, the study began with Snowdon meeting with 1,000 nuns to discuss his project. He laid out the basic proposal. The research team sought volunteers aged 75 and older. The sisters would have to turn over all their biographical writings and participate in a series of interviews and cognitive tests at least once per year. Critically, any sister who participated in the project would need to donate their brain to the research team following their death, allowing researchers to compare demented and nondemented brains. When Snowdon ended the presentation by asking for volunteers, Sister Mary was the first to sign up. 638 nuns followed her lead and participated in the study. 

Mental State Examination
Mental State Examination

The first step was to test each participant’s cognitive ability with the Mental State Examination. The exam included a handful of smaller tests. For example, participants were asked to name as many animals as possible in 60 seconds or draw complex shapes by connecting seemingly random lines. Researchers would read a list of words, then ask the participant to repeat as many as possible. The test results were aggregated and scored out of 30. Anything above 24, or 80%, was considered healthy cognitive function.

There were participants at every age level that failed the test, but most women in their 70s scored within the healthy range. At 85, the average score was just below the 80% mark. By age 95, the average score was closer to 50%. Only one nun above 100 years old ever passed the test—that was Sister Mary.

Following the preliminary evaluations, Snowdon refined his research question, asking if linguistic ability in early life was associated with cognitive function and Alzheimer’s disease in late life. He tested this by looking over the biographical journal entries the sisters wrote in the 1920s and 30s.

The researchers analyzed the writing for idea density and grammatical complexity. Researchers defined idea density as the number of distinct concepts expressed per 10 words. The writings were easy to compare, as each entry was approximately 300 words and described the author’s life before entering the convent. The analysis yielded clear results—the women who wrote idea-heavy, grammatically complex essays had much higher cognitive function into their 80s and 90s. 

This was a compelling result. The fact that someone’s linguistic ability in their 20s could affect health outcomes in their 90s was remarkable. But this was just the beginning of Snowden’s findings. 

The research team adjusted their analysis. Rather than looking for indications of intellect, they sought signs of emotion. Words that expressed feelings were coded and separated into three categories: positive, neutral, and negative. Positive words expressed accomplishment, amusement, contentment, gratitude, happiness, hope, interest, love, and relief. Expressions of anger, contempt, disgust, disinterest, fear, sadness, and shame were coded as negative. The only neutral emotion was surprise. 

The texts were rated on their level of positive emotion. Unsurprisingly, nuns aren’t the most overtly pessimistic people. But a lack of enthusiasm marked many of the essays. 

An example with low positive emotionality may read like so: I was born on September 26, 1909, the eldest of seven children, five girls and two boys … . My candidate year was spent in the Motherhouse, teaching Chemistry and Second Year Latin at Notre Dame Institute. With God’s grace, I intend to do my best for our Order, for the spread of religion, and for my personal sanctification. 

On the other hand, here’s a highly positive example: God started my life off well by bestowing upon me a grace of inestimable value… . The past year which I have spent as a candidate studying at Notre Dame College has been a very happy one. Now I look forward with eager joy to receiving the Holy Habit of Our Lady and to a life of union with Love Divine.

The nuns were separated into four quartiles based on their scores—the First Quartile hardly uttered an appreciative word, while the Fourth Quartile was bursting at the seams with appreciation and warmth. 

When Snowdon followed up with the participants several years after the initial study, 42% of the sisters had passed away. But, the identities of those participants revealed something huge. Women in the bottom two quartiles were 2 to 3 times more likely to have passed away. In other words, more than half of the least positive women had died, and just a quarter of the most positive died. 

But, it turned out, expressing negative emotion was better than showing no emotion at all. The sisters most likely to have passed away weren’t those that voiced negative feelings—it was those who expressed no feelings at all. Thus, simply venting one’s sentiments, good or bad, led to better outcomes.

Snowdon was shocked. Demonstrating that emotional expression and positivity led to longer, healthier lives was beyond what he had initially hoped for. So he adjusted his hypothesis to state that positive emotions deterred the brain changes that led to Alzheimer’s. Yet, believe it or not, the most shocking revelation was yet to come. 

With 678 participants, Snowdon’s team had 678 brains to analyze after each sister’s passing. The contributions of this goodhearted group made up the largest donation of healthy brains in human history. When Sister Mary passed on at 101 years old, the research team expected to find a healthy-looking brain. After all, she scored a 27 out of 30 on her final examination. Yet, Snowdon discovered that Sister Mary’s brain was full of neurofibrillary tangles and senile plaques—the physical indicators of Alzheimer’s. 

Healty brain VS severe AD ( Alzheimer Desease )
Healty brain VS severe AD ( Alzheimer Desease )

If the doctors looking at Sister Mary’s brain hadn’t been aware of her cognitive ability, they would have predicted that she was suffering from dementia. This meant one of two things. First, perhaps the medical field still didn’t understand the physical causes of Alzheimer’s. Or, second, qualities like positivity and high-level linguistic skills inhibit dementia’s onslaught, even if the person fits the criteria for having Alzheimer’s. It seems that the answer is a mixture of both of these conclusions.

But, with that answer comes one final question: how? How do positivity and emotional expression lead to a longer, healthier life? Thankfully, many qualified researchers have asked this same question and come up with several relevant answers.

Negative emotions like stress, fear, and anxiety cause physical responses, like high blood pressure and an increased heart rate. Both of these responses can contribute to heart disease. Other people experience headaches, stomachaches, or, in extreme circumstances, ulcers. Similarly, suppressing any emotions can lead to negative physical responses.

Follow-up studies on the benefits of venting emotions are mixed. It seems that expressing negative feelings can help in the short-term but may have little effect long-term. Replacing pessimism with optimism doesn’t necessarily reduce the health consequences. Rather, more optimistic people experience fewer negative emotions in the first place. This stems from the belief that things will get better no matter how bad they are now. Unfortunately, this means that habits like writing in a gratitude journal will have little impact on someone whose days are filled with anxiety and depression.

Still, there is a handful of essential takeaways from Snowdon’s Nun Study. First, emotionality and linguistic skill are strong predictors of late-life cognitive health. Improved early-life education in mental health and reading and writing fluency could deter late-life cognitive decline.

Second, brain function is not wholly dependent on the brain’s physical state. People with healthy mental habits can overcome the material changes caused by Alzheimer’s. 

Third, and perhaps most importantly, the Nun Study showed that we have a long way to go in our understanding of the human mind despite advances in cognitive science. There is still a shortage of healthy brains for scientists to research. Progress in this field will continue at its slow pace unless] more people like Sister Mary donate their brains to science. Then, perhaps one day, we can put an end to Alzheimer’s once and for all.

So what do you think? What firm conclusions can we draw from the nun study? How will you apply these findings to your life? Will improvements in education and mental health resources reduce dementia? Can we increase the supply of healthy brains for scientific research morally, without breaching individual rights? What are your plans for your brain once you pass on?

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