Snowdon's Nun Study
Wednesday 4 July 2012
Perhaps no study of Alzheimer’s disease is more intriguing that Snowdon’s Nun study. The study is a great example of a longitudinal, retrospective case study. The study could be used to look at the interaction of cognition and biological factors in memory. It could also be used as a good example of how a case study is used in the cognitive level of analysis.
678 members of the School Sisters of Notre Dame in the U.S. participated in the Nun Study, a longitudinal study of aging and Alzheimer's disease which began in 1986. The homogeneous life style of the nuns makes them an ideal study population. Participants in this study are nonsmokers, drink little if any alcohol, have the same marital status and reproductive history, have lived in similar housing, held similar jobs, and had similar access to preventive and medical care. This minimizes the extraneous variables that may confound other similar research
Researchers accessed the convent archive to review documents collected during the lives of the nuns. Among the documents were autobiographical essays that had been written by the nuns upon joining the Sisterhood. It was found that an essay's lack of linguistic density (e.g., complexity, vivacity, fluency) was as a significant predictor of its author's risk for developing Alzheimer's disease in old age. The approximate mean age of the nuns at the time of writing was 22 years. Roughly 80% of nuns whose writing was measured as lacking in linguistic density went on to develop Alzheimer's disease and lesions on the brain in old age; meanwhile, of those whose writing was not lacking, only 10% later developed the disease.
Snowdon believed that full development of the brain and cognitive abilities early in life, through education or other stimulation, may protect people from Alzheimer s disease and cognitive problems later. Educational differences, however, did not explain the relationship between low linguistic ability in early life and poor cognitive function later on. Psychologists have now developed an alternate theory -- that low linguistic ability in early life could be a subtle symptom of very early changes in the brain that ultimately lead to Alzheimer's disease.
With Snowdon’s retirement from the project, the University of Minnesota has agreed to oversee the research. For more information on the future direction of the project, see the video clip below. For more information on the study, see Snowdon’s book, Aging with Grace: What the Nun Study Teaches Us About Leading Longer, Healthier, and More Meaningful Live.