The Nun Study is a longitudinal study of aging and Alzheimer's disease conducted by Dr. David Snowdon and the University of Kentucky. The nun study began in 1986 and studies a group of American Roman Catholic sisters who are members of the School Sisters of Notre Dame. By studying a relatively homogeneous group (no drug use, little or no alcohol, similar housing and reproductive histories, etc.) minimizes the extraneous variables that may confound other similar research. Researchers have also accessed the convent archive to review documents through the lives of the participants of the study. One such document reviewed was an autobiographical statement that participants made when joining the Sisterhood, the complexity and fluency of which (or lack there of) has been shown to be a significant predictor of the onset of Alzheimer's disease. (wikipedia)