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For 15 years, David Snowdon, PhD, has deeply involved himself in the lives and deaths of 678 nuns, all members of the Roman Catholic School Sisters of Notre Dame. Snowdon’s quest to unravel the mysteries of the human brain and the process of aging and dying has begun to reveal the intertwining relationships between longevity, Alzheimer’s disease, education, and the thought process. His work has rocked the scientific, medical, and psychological communities — and promises to continue to do so for another 20 years or more. Snowdon, an epidemiologist and professor of neurology at the Sanders-Brown Center on Aging at the University of Kentucky in Lexington, has discovered truisms about human aging that have quickly become assimilated into our psyches. Some examples include:
• If you’re happy, you’re likely to live longer.
• Education and a life-long use of mental faculties reduces the symptoms of Alzheimer’s disease.
• Alzheimer’s appears to have its roots early in life, and there are many lifestyle factors, including education, nutrition, exercise, depression, and cardiovascular health that seem to play a role in its development.
• Complex thought patterns early in life may provide a life-long protection against loss of cognitive function.
• Ordinary foods in the diet can protect the brain.
• Intangibles like positive spirit, the support of community, and faith contribute to health and longevity.
"I think the most important thing we are learning from the Nun Study is how essential it is to stimulate our children’s minds early in life," says Rosa Li, PhD, director of public policy at the National Institute on Aging in Bethesda, MD. What we can learn from these remarkable nuns, many of whom have lived long beyond the century mark, is that by doing something as simple as reading to our children, we can offer them a boost toward a long and healthy life, says Li.
Before Snowdon began the Nun Study, he researched the lives of tens of thousands of participants, largely Lutherans and members of the Seventh Day Adventist Church. When he first sought permission to study the School Sisters of Notre Dame, the congregation’s leader, Sister Carmen Burg, agreed on one condition — that Snowdon treat the sisters as human beings and not as research subjects. "She told me to go to the convents and get to know them as individuals," says Snowdon. "This of course flies in the face of the way scientists are trained in the name of objectivity.’ But what a gift. I now have honorary great-nephew status with a group of remarkable women."
The nuns provided a treasure house of information for Snowdon and data unlikely to be replicated in any other setting since the women, ages 75 to 106 years, were available for the long-term needs of the study. They live in a communal setting with similar dietary intakes. They do not smoke, and they have no children. Each woman has agreed to donate her brain to the research process when she dies. "Nuns are an ideal group to study because they live such similar lives — that makes it easier to home in on the differences that really count," says Snowdon.
One of the greatest treasures Snowdon discovered in the congregation’s archives, were one- and two-page autobiographies written by the nuns when they were in their early 20s, just before they took their religious vows. "When we first discovered them, it was like we opened a fascinating time capsule," he says. "We have since discovered they have amazing predictive power."
For example, a linguistic measure called idea density was applied to the autobiographies, and it predicted who would get Alzheimer’s 60 years later with 80% accuracy. "The sisters who packed the most ideas into their sentences at age 22 were somehow protected at age 85," Snowdon marvels. "We still don’t know exactly what brain mechanism is involved, but other research has shown that Alzheimer’s may be a life-long process," he adds.
Another study, recently published, shows that the nuns who expressed the most positive emotions in their autobiographies lived longer on the average than those who expressed the least emotions. "Maintaining a positive attitude appears to be very important to living a long and healthy life," says Snowdon. Snowdon also has been perplexed by apparent contradictions in the post-mortem examinations of some of the nuns’ brains and their cognitive function in life. "We have discovered sisters with the most extensive form of Alzheimer’s damage in their brains who performed brilliantly on our mental tests. We have discovered that a sister may be severely demented without having significant brain damage. In other words, the symptoms don’t always match the pathology," he says.
Snowdon’s team also found that the cumulative brain damage caused by small strokes may tip the balance toward dementia. "Ultimately, that is good news, because we do know how to prevent strokes."
The Nun Study also has discounted two popular myths about the cause of Alzheimer’s — the use of aluminum in soda cans and cookware and mercury in dental fillings. "They’re not factors," says Snowdon. Another piece of good news, says Snowdon: "Some of the healthiest brains we have found are in centenarians. So, even if we become extremely old, decline is not inevitable." The School Sisters of Notre Dame are extraordinarily long-lived, with a risk of death at any given year beyond age 65 at about 25% less than that of the general population of women in the United States.
What can medical professionals give to patients and families that might duplicate this longevity? "Certainly education and a prudent healthy lifestyle play important roles — for example, none of the sisters smoke. But I believe that intangibles such as positive life purpose, spirituality, and a supportive community also are important," Snowdon says.
(For more information: The latest results can be found at the Nun Study web site: www.mc.uky.edu/nunnet/ or www.nunstudy.org. Also, see: Snowdon D. Aging with Grace. New York City: Bantam Books; 2001.)