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Not even close. Snowdon's study attracted the attention of leading Alzheimer's researchers, who explained to him that the elderly women represented an ideal population for studying this mysterious disease. On average, 10% of people over 65 come down with Alzheimer's, a number that rises to 50% by age 85. Given the aging population of the convent, they knew that a significant proportion of the nuns would have the disease.
The most serious drawback to studying the sisters for Alzheimer's is that there's only one sure way to diagnose it: examine the patient's brain after he or she dies. If he were to proceed, Snowdon would need written permission to perform autopsies, not only on the Mankato nuns but also, to get a large enough sample, on members of the order at six other Notre Dame convents as well. "They really had to trust us," he says. "We could have turned out to be Dr. Frankensteins for all they knew."
So one day in 1990, a nervous Snowdon stood in front of the assembled sisters in Mankato, many of whom he'd got to know as friends, and made his pitch. "We sat in our chairs and held our breath," recalls Sister Rita Schwalbe, who by then had joined Snowdon's research team. "Then one of the sisters piped up, 'He can have my brain, what good is it going to do me when I'm six feet under?' And that broke the ice."
In all, more than 90% of the sisters living in the Mankato convent agreed to donate their brains. After visiting six other convents, Snowdon ended up with a 68% consent rate overall, one of the highest in any tissue-donation study. "I didn't really know what it was going to be about," says Sister Nicolette, an engaging 93-year-old who is the only one of the 16 girls who took their vows in 1925 to both survive and remain mentally intact. "But I thought if science could learn something from this program, then I was glad to be a part of it." In 1991, the first participant, a resident of Good Counsel Hill convent, died, and the Nun Study received its first brain.
Snowdon, who had accepted a position at the University of Kentucky's Sanders-Brown Center on Aging, was working with a team of neurologists and psychologists to devise a battery of tests for assessing the sisters' mental and physical abilities--tests that could later be correlated with the results of brain exams. He joined forces with James Mortimer, an eminent researcher on aging then at the Minneapolis Veterans Administration Medical Center, to study the nuns' youthful autobiographies in more detail, and their relationship led to an interesting discovery: autopsies by other scientists had shown that the physical destruction wrought by Alzheimer's didn't inevitably lead to mental deterioration. The reason, according to one leading theory, was that some folks might have an extra reserve of mental capacity that kept them functioning despite the loss of brain tissue.
So he and Mortimer, along with University of Kansas psychologist Susan Kemper, began analyzing the autobiographies for evidence of such extra capacity. Kemper, an expert on the effects of aging on language usage, had earlier shown that "idea density"--the number of discrete ideas per 10 written words--was a good marker of educational level, vocabulary and general knowledge. Grammatical complexity, meanwhile, was an indicator of how well memory was functioning.