Alzheimer’s is described as one of old age’s most feared illnesses, affecting memory, thinking, and daily functioning, and it is the most common cause of dementia. More than 7 million Americans age 65 and older are living with the disease, and the number is still rising. Against that backdrop, one of the most influential aging studies focused on an unusual group, Catholic nuns.
The Nun Study began in 1986, when American epidemiologist Dr. David Snowdon set out to examine the link between aging and health in a population with few lifestyle differences. He chose sisters from the Notre Dame order in the United States, who had lived for decades with similar diets, access to medical care, income levels, and very low rates of smoking and alcohol use. That made them an unusually controlled group for studying what really affects brain health over time.
In 1996, the study expanded to 678 nuns ages 75 to 102. They agreed to cognitive testing, to share personal writings from throughout their lives, and to donate their brains after death. Over the next three decades, researchers examined more than 600 brains, allowing them to compare brain pathology with how the women had actually performed mentally during life.
Among the key findings was a clear link between education and dementia risk. Nuns with university degrees tended to preserve memory and thinking better than those with only basic schooling. Researchers also found that richer, more complex language in autobiographies written in the early 20s was associated with a lower risk of dementia decades later, suggesting some brain resilience is shaped very early in life.
The study also showed that some women functioned normally even when autopsies found clear Alzheimer’s changes in their brains. Scientists call this "cognitive resilience," meaning the brain can sometimes compensate for damage and preserve function. Other contributors to decline included vascular damage, small strokes, hippocampal shrinkage, and changes in certain proteins. Nuns carrying the APOE ε4 variant were at higher risk, but education and lifestyle still influenced the speed of decline. Nearly 40 years after it began, the study continues to shape Alzheimer’s research by showing that brain health is built long before old age.
