How hundreds of religious sisters contributed to ‘groundbreaking’ 30-year Alzheimer’s study
null / Credit: Elena Ray/Shutterstock CNA Staff, Mar 14, 2025 / 06:00 am (CNA).
The contribution of nearly 700 Catholic religious sisters to a “groundbreaking” decades-long study on Alzheimer’s and dementia continues to offer important information for maintaining “cognitive health” across the lifespan, researchers say.
Launched in 1986 by neurologist David Snowdon, the “Nun Study” produced “seminal findings” on “cognitive impairment and related neuropathologies,” researchers said in a historical review published at Alzheimer’s & Dementia journal last month.
Kyra Clarke, a doctorate student at UT Health San Antonio and one of the authors of the February review, said Snowdon opted to use Catholic sisters for the monumental study after he “realized that studying nuns came with many advantages for dementia research.”
“Normally, it’s hard to pinpoint what causes some people to develop dementia while others remain healthy because people can have very different lifestyles, environments, and biology — some smoke, some don’t; some have better access to health care than others; some may be more genetically disposed to disease,” she said.
“But Catholic sisters from the same order share the same environment for most of their adult lives: similar marital histories, housing, nutrition, health care, income, and social networks,” she pointed out.
“It is difficult to find a community of people with such consistent and comparable lifestyles. This makes it easier to figure out what factors truly increase or decrease the risk of dementia.”
Snowdon launched the pilot study of the program in 1986 in cooperation with the School Sisters of Notre Dame (SSND), with a pool of 678 sisters eventually being drawn out of 1,000 candidates from what were then seven main convents across the country, including in Chicago, Baltimore, Dallas, and elsewhere.
The age of the sisters at the outset of the study ranged from 75 to 102. All had similar life histories, while the vast majority were at least college graduates, with nearly 90% having been teachers at some point.
Researchers used a variety of methods to gauge progression of cognitive function of the sisters later in their lives, including autobiographies the nuns wrote prior to taking their vows, medical records, academic transcripts, and questionnaires.
The sisters “consented to participate in neuropsychological assessments and permitted researchers access to personal records kept by the convents,” researchers said; they were further required to agree to brain donation upon their deaths for the scientists to study.
Clarke said the sisters exhibited ”extraordinary dedication and enthusiasm” for the study, particularly as evidenced by the high numbers of them who agreed to participate.
“A 66% participation rate is a truly impressive amount for a longitudinal study requiring participants to undertake extensive cognitive testing every year for the rest of their lives and agree to brain donation as well,” she noted.
The inclusion of healthy as well as cognitively impaired sisters was a critical factor in the study, the researchers said, as it “allowed for the longitudinal tracking of cognitive changes through annual assessments.”
The high brain donation rate likewise “provided the opportunity to compare neuropathology findings from the autopsied brains of impaired individuals with healthy control brains, which had been historically difficult.”
The findings of the study have “significantly advanced” understanding of Alzheimer’s disease and related dementias. One key discovery, Clarke said, was that “higher early-life cognitive ability seems to be protective against dementia.”
“Researchers found that sisters with higher educational attainment and academic performance (based on school transcripts stored in convent archival records) had higher scores on cognitive tests in late life and lower risk of dementia,” she said. Religious sisters with better written language skills earlier in life were also at a lower risk for 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.
All of the sisters in the study have since passed away. In some cases the research has taken on personal significance: multiple family members of Margaret Flanagan, the director of the ongoing Nun Study at UT Health, attended Chicago’s Academy of Our Lady run by SSND sisters.
Researchers, meanwhile, continue to meet with representatives of the SSND to provide updates on the ongoing data.
The scientists are “deeply appreciative of their dedication to education and helping the lives of others,” Clarke said.
“Their kindness and generosity made the Nun Study an iconic and groundbreaking contribution to dementia research and continuously inspires us to keep pushing towards understanding and treating this debilitating disease,” she said.
