“The Nun Study” refers to a well-known study conducted at School Sisters of Notre Dame convents by Dr. David Snowdon that revealed new understandings of Alzheimer’s Disease (AD).[1] Studying the risk factors and onset of AD and dementia in nuns turned out to be one of the most ideal scenarios for long term research on disease. These women had similar lifestyles, socioeconomic status, access to health care, and social support.[2] None of these women had ever been married or had children, which gave them each similar risk for certain cancers and other diseases. Astonishingly, several of the nuns had agreed to donate their brains to research after their deaths, which helped the researchers predict which factors influenced cognition throughout the nuns’ lives.[3] Furthermore, Snowdon had access to autobiographies each of the women had written in their 20s, which allowed him to compare cognitive abilities early in life to the women’s present state. Ultimately, most confounding variables present in most human studies had been removed and Snowdon and his team had a wealth of information to conduct their study.[4] While there is still much to learn about AD and dementia, the Nun Study has revealed new and valuable information on the pathology of this devastating disease.
Idea Density vs. Dementia
One of the most precious pieces of this study were the autobiographies each woman had written upon entering the convent decades earlier. Snowdon and his team carefully read each one and calculated an “idea density” score, which attributed a numeric value for the number of discrete ideas written per 10 words in a sentence. Astonishingly, they found that there was a strong positive association between idea density in early life and presence of dementia later in life. Research suggests that nuns who had lower idea density scores had an increased risk for developing dementia and had a lower life expectancy, while nuns with higher scores tended to live a long, dementia-free life. The association was so direct that Snowdon could predict which nuns might have dementia simply by reading their letters. Many of the women who had high idea density scores had also received secondary education, and in many cases, had earned their Master’s degree or had spent several years working as teachers. [5] These findings highlight the importance of higher education and cognitive sharpening throughout life by engaging in reading, writing, and other activities that involve focus and learning.
Nutrition, Folate & Dementia
Although the nuns were fed similar foods from the same kitchen, each had their own food preferences, which allowed for some variation in disease pathology. Upon analysis, nuns exhibiting dementia and AD-like behavior consistently had low levels of folate in their blood. Low folate levels were correlated with atrophy of the neocortex in the brain and a decrease in cognitive abilities. Research suggests that folate has a crucial role in development of the central nervous system (CNS) and in the reduction of homocysteine. Reduction of homocysteine is noteworthy, because there’s a strong association between elevated homocysteine and vascular disease, which contributes to the risk of a stroke or heart attack that can damage the brain.[6] Nutritional analysis also revealed that nuns with high amounts of lycopene in their diets had a reduced risk for developing dementia and appeared to age healthily. Lycopene is an antioxidant and the red pigment found in tomatoes and watermelon.[7] Although there is still much research to be done on nutritional factors, it is never too soon to adopt preventative practices, such as consuming folate- and antioxidant-rich foods, to avoid age-related cognitive decline.
One Nun Against the Odds
While it is true that genes and physical attributes of the brain are large factors in disease risk and presence, one impressive piece of the study was the life and death of Sister Mary. Sister Mary is referred to as the “gold standard” of healthy aging because of the vibrant and full life she lived for over 100 years. Upon her death, analysis of her brain revealed several lesions and other signs of AD that should have caused her to have poor cognition and other health problems. However, she enjoyed reading, knitting, and socializing up until her death. It is thought that her lifelong career as a teacher along with a well-balanced diet and proclivity for reading helped her defy physical and genetic predisposition to dementia. Sister Mary’s story is a hopeful example of how clinical expression of some diseases can be avoided by lifestyle factors. Preventative measures put forth by the Nun Study include protecting the head from physical damage (e.g. concussions), avoiding tobacco, exercising regularly, and eating a healthy, balanced diet.[8]
The Nun Study in Depth
There are some great resources for learning more about the study, including The University of Minnesota’s Nun Study homepage, and a Youtube video. To find out more about Dr. Snowdon, the nuns of the School Sisters of Notre Dame, and AD-risk factors check out Dr. Snowdon’s book, Aging with Grace: what the nun study teaches us about leading longer, healthier, and more meaningful lives.[9]
Resources
[1] Lemonick, M. D., & Park Mankato, A. (2001). The Nun Study: How one scientist and 678 sisters are helping unlock the secrets of Alzheimer’s Disease. Time Magazine. Retrieved from http://cdn2.hubspot.net/hub/66537/file-15875856-pdf/docs/thenunstudy-m.lemonick.pdf.
[2] Op. cit. Lemonick (2001); Snowdon, D. A. (1997). Aging and Alzheimer’s disease: lessons from the Nun Study. The Gerontologist, 37(2), 150-156; Snowdon, D. A., Tully, C. L., Smith, C. D., Riley, K. P., & Markesbery, W. R. (2000). Serum folate and the severity of atrophy of the neocortex in Alzheimer disease: findings from the Nun study. The American journal of clinical nutrition, 71(4), 993-998.
[3] Snowdon, D. A. (2003). Healthy Aging and Dementia: Findings from the Nun Study. Annals of Internal Medicine, 139(5), 450-454.
[4] Op. cit. Snowdon (2003); Snowdon (1997).
[5] Op. cit. Snowdon (2003); Snowdon (1997); Lemoncik (2001); Danner, D. D., Snowdon, D. A., & Friesen, W. V. (2001). Positive emotions in early life and longevity: findings from the nun study. Journal of personality and social psychology, 80(5), 804; Snowdon, D. A., Greiner, L. H., & Markesbery, W. R. (2000). Linguistic ability in early life and the neuropathology of Alzheimer’s disease and cerebrovascular disease: Findings from the Nun Study. Annals of the New York Academy of Sciences, 903(1), 34-38.
[6] Snowdon, D. A., Tully, C. L., Smith, C. D., Riley, K. P., & Markesbery, W. R. (2000). Serum folate and the severity of atrophy of the neocortex in Alzheimer disease: findings from the Nun study. The American journal of clinical nutrition, 71(4), 993-998
[7] Op. cit. Lemonick (2001); Snowdon (2000); Kirkwood, T. (2003). Aging with grace. the nun study and the science of old age: How we can all live longer, healthier and more vital lives. Ageing and Society, 23, 255-256.
[8] Op. cit. Snowdon (2003); Snowdon (1997); Lemoncik (2001); Snowdon (2000); Kirkwood (2003).
[9] Snowdon, D. (2008). Aging with grace: what the nun study teaches us about leading longer, healthier, and more meaningful lives. Random House Publishing Group.
Clinical Contributor
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Disclaimer: The information provided is only intended to be general educational information to the public. It does not constitute medical advice. If you have specific questions about any medical matter or if you are suffering from any medical condition, you should consult your doctor or other professional healthcare provider.
