What 678 Nuns Taught Us About Preventing Alzheimer’s

In 1986, a scientist named Dr. David Snowdon began one of the most extraordinary studies in the history of brain research. He didn't go to a hospital or a clinic.

He went to a convent.

Over the following decades, Dr. Snowdon recruited 678 Catholic nuns from the School Sisters of Notre Dame — women aged 75 to 107 — for what would become known simply as The Nun Study. Each sister agreed to annual cognitive and physical tests, gave access to their personal records and medical histories, and — crucially — donated their brains to science after death.

The nuns were a researcher's dream.

• They lived together

• Ate the same food,

• Didn't smoke or drink heavily, and

• Had similar daily routines.

This eliminated many of the lifestyle variables that muddy most long-term studies. What was left were the things that truly mattered.

The results were remarkable — and sometimes baffling. When the nuns' brains were examined after death, some had all the physical hallmarks of advanced Alzheimer's disease: the plaques, the tangles, the tissue damage.

Yet these same women had shown no signs of dementia while alive. They were sharp, engaged, and mentally vibrant right to the end.

One shining example was Sister Mary, who scored highly on cognitive tests at age 101 — despite her brain showing extensive Alzheimer's pathology.

How was that possible?

The answer pointed to something researchers now call cognitive reserve: the brain's ability to compensate for damage by drawing on stronger, richer neural networks built up over a lifetime.

One of the study's most surprising discoveries came from the sisters' own handwriting — specifically, autobiographies they had written as young women before taking their vows. Nuns who wrote in complex sentences with high "idea density" — packing more meaning into fewer words — were dramatically less likely to develop Alzheimer's decades later.

In fact, those with richer early-life language skills had 20% higher cognitive scores in old age, even when their brains showed physical signs of the disease.

The study also found that positive emotions played a powerful role. Nuns whose autobiographies expressed more joy, gratitude, and hope lived up to 10 years longer than their less optimistic peers — and had far lower rates of dementia.

Low levels of folic acid (vitamin B9) were linked to greater brain shrinkage, while strokes — even small, silent ones — dramatically accelerated cognitive decline in those already vulnerable.

The Nun Study offers some of the most hopeful news in brain research: your daily habits genuinely matter. Here's what the science suggests:

• Keep learning. Read, write, take courses, learn a language or instrument. Building cognitive reserve is a lifelong project.

• Stay positive. Cultivating gratitude, joy, and purpose isn't just good for your mood — it may protect your brain.

• Eat your greens. Folic acid (found in leafy vegetables, legumes, and fortified foods) appears to protect the brain from shrinkage. Aim for 400 micrograms daily. You can also get folate (the natural form of folic acid) from organ meats, shellfish and fatty fish.

• Protect your heart and blood vessels. What's good for the heart is good for the brain. Manage blood pressure, stay active, and avoid smoking.

• Stay socially and mentally engaged. The nuns lived purposeful, communal, intellectually active lives well into old age — and it showed in their brains.

The nuns didn't set out to teach us about Alzheimer's. But in their generosity, they gave science — and all of us — a roadmap for a sharper, longer life.