The Nun Study Revealed Hidden Details About Dementia and Alzheimer’s. Now a New Era of Research Begins
Nearly every modern idea about why some brains resist Alzheimer’s while others do not traces back to a group of Catholic sisters who agreed, decades ago, to let scientists follow them for the rest of their lives. The nun study, launched in 1990 with 678 members of the School Sisters of Notre Dame, is back in focus after a 2025 scientific review reexamined what the project taught researchers about aging and dementia.
Every sister who took part has now died. Their brain donations continue to power new research, and a new generation of scientists is still publishing findings from the archive they left behind.
How the Nun Study Began
The project grew out of a 1986 pilot led by David Snowdon, Ph.D., who wanted to understand the link between education and aging-related disorders. He expanded that work in 1990 into the full nun study, a longitudinal investigation of aging and Alzheimer’s disease that eventually enrolled 678 School Sisters of Notre Dame across the United States, according to a 2025 review published in Alzheimer’s & Dementia the Journal of Alzheimer’s Association.
Most participants were between 75 and 102 years old at enrollment. Of the 1,027 eligible women, 678 (66%) agreed to annual assessments of memory, language and reasoning, along with regular checks on physical health and daily functioning. Each sister also consented to donate her brain after death, a commitment the School Sisters of Notre Dame describe on their website as central to the project.
Why Researchers Chose Catholic Sisters for a Dementia Study
Kyra Clarke, a doctorate student at UT Health San Antonio and one of the review’s authors, said Snowdon “realized that studying nuns came with many advantages for dementia research,” according to EWTN News.
Sisters in the same religious order share housing, nutrition and health care for most of their adult lives. They also share similar income levels and social networks, Clarke said, which strips away many of the variables that muddle typical population studies. In this cohort, 85% had earned at least a bachelor’s degree, and 89% had worked as teachers.
“It is difficult to find a community of people with such consistent and comparable lifestyles,” Clarke said. “This makes it easier to figure out what factors truly increase or decrease the risk of dementia.”
What the Nun Study Found About Alzheimer’s
Researchers combined yearly cognitive testing with medical records and educational transcripts. They also studied autobiographies the sisters had written in early adulthood and analyzed genetic samples. By the end of the study, 98% of participants had undergone brain autopsy, and more than 600 brains were examined by neuropathologists who did not know how the sisters had performed on cognitive tests during life.
Some sisters had significant Alzheimer’s-related changes in their brains, including amyloid plaques and neurofibrillary tangles, yet never developed dementia. Early-life cognitive ability, measured through those old autobiographies and school records, tracked with better cognitive outcomes decades later. Together these results helped establish the concept of cognitive reserve, the idea that lifelong mental activity may protect thinking and memory even when disease is present in the brain.
The findings also showed that multiple brain diseases often coexist in older adults and that these overlapping pathologies raise the odds of developing dementia.
“The Nun Study really emphasized that maintaining cognitive health is a lifelong task and emphasized the importance of education and cognitive stimulation in reducing the risk of dementia,” Clarke said.
Why the Nun Study Still Matters
The project also linked nutrition to brain health. Sisters with lower blood folate (vitamin B9) levels tended to show greater brain shrinkage and weaker cognitive performance, particularly when their homocysteine levels were elevated. The findings did not prove that folic acid prevents Alzheimer’s, but they suggested adequate folate may be part of healthy brain aging.
Margaret Flanagan, who now directs the ongoing nun study at UT Health, has family members who attended a Chicago school run by the School Sisters of Notre Dame. Researchers continue to meet with representatives of the order to share updates.
“The Nun Study has certainly been pioneering,” Dr. Richard Suzman, chief of demography and population epidemiology at the National Institute on Aging, told The New York Times. “It’s helped change the paradigm about how people think about aging and Alzheimer’s disease.”
This article was created by content specialists using various tools, including AI.
