The Religious Orders Study (ROS) is a longitudinal, epidemiologic clinical-pathological study of memory, motor, and functional problems in older Catholic nuns, priests, and brothers aged 65 years and older from across the United States. Participants without known dementia agree to medical and psychological evaluation each year and brain donation after death. Since 1994, approximately 1,200 older persons have been enrolled and 580 are currently alive. Participants also have yearly blood draws which result in the storage of serum, plasma and cells.

The Memory and Aging Project (MAP) is a longitudinal, epidemiologic clinical-pathologic study of dementia and other chronic diseases of aging. Older persons are recruited from about 40 continuous care retirement communities and senior subsidized housing facilities around the Chicago metropolitan area. Participants without known dementia agree to annual detailed clinical evaluation and donation of brain, spinal cord and muscle after death. MAP began in 1997 and over 1,600 older adults have enrolled. Approximately 1,000 participants are currently alive. Participants also have yearly blood draws which result in the storage of serum, plasma and cells.

Clinical evaluation, self-report, and medication inspection are used to document medical conditions. The diagnostic process is the same for ROS and MAP. Briefly, a decision tree designed to mimic expert clinical judgment was implemented by computer to inform several clinical diagnoses, including dementia and AD. It combines data reduction techniques for the cognitive performance testing with a series of discrete clinical judgments made in series by a neuropsychologist and a clinician. Presumptive diagnoses of dementia and AD are calculated that conform to accepted clinical criteria. The clinician is asked to agree or disagree with the decisions. An algorithm uses these decisions to provide diagnoses of MCI and amnestic MCI. Persons with MCI are judged to have cognitive impairment by neuropsychologic testing without a diagnosis of dementia by the clinician. Persons without dementia or MCI are categorized as having no cognitive impairment (NCI).