The Chicago Healthy Aging Project (CHAP) is a longitudinal population study of an urban general population sample (n= 10,000+) lasting from 1993 to 2012 of common chronic health problems of older persons, especially of risk factors for incident Alzheimer’s disease, based in three neighborhoods on the south side of Chicago.  An initial enrollment was supplemented by enrollment of successive age cohorts of community residents as they attained the age of 65.  After the enrollment period, the CHAP pursued a complex strategy for follow-up evaluations, interviewing all participants about every three years and conducting in-depth clinical evaluations among a stratified random sample of participants at each of these cycles. Cognition was assessed for all CHAP subjects and the presence of Alzheimer’s disease (AD) was assessed for those in the Clinical Evaluation sample.

Clinical evaluation included a neuropsychological battery, structured neurological examination and medical history.  For persons in whom there was evidence of dementia and uncertainty as to whether a stroke had occurred or its relation to detention, limited diagnostic use of brain magnetic resonance imaging (MRI) occurred.  Diagnosis of dementia required loss of cognitive function by the neurologist’s assessment and impairment in two or more functions on cognitive performance tests. The diagnosis of Alzheimer’s disease was by criteria of the National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer’s Disease and Related Disorders Association (NINCDS/ADRDA) for probable Alzheimer’s disease.