Sister Mary, the gold standard for the Nun Study, was a remarkable wom
an who had high cognitive test scores before her death at 101 years of
age. What is more remarkable is that she maintained this high status
despite having abundant neurofibrillary tangles and senile plaques, th
e classic lesions of Alzheimer's disease. Findings from Sister Mary an
d all 678 participants in the Nun Study may provide unique clues about
the etiology of aging and Alzheimer's disease, exemplify what is poss
ible in old age, and show how the clinical expression of some diseases
may be averted.