Accurate clinical staging of dementia in older subjects has not previously been achieved despite the use of such methods as psychometric testing, behavioural rating, and various combinations of simpler psychometric and behavioural evaluations. The Clinical Dementia Rating (CRD), a global rating device, was developed for a prospective study of mild senile dementia--Alzheimer type (SDAT). Reliability, validity, and correlational data are discussed. The CRD was found to distinguish unambiguously among older subjects with a wide range of cognitive function, from healthy to severely impaired.

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SUMMARY Clinical investigations of senile dementia of the Alzheimer type require establishment of explicit clinical diagnostic criteria before histological confirmation is possible. Criteria for selection of mildly impaired subjects with senile dementia of Alzheimer type, free of other major disease, are proposed. Problems of recruitment of this select population for a longitudinal study are discussed. A study population with matched healthy control subjects has been enrolled and described. Short term follow-up has provided preliminary support for the diagnostic criteria.The most frequent cause of dementia in persons over age 65 is senile dementia of the Alzheimer type (SDAT), multi-infarct dementia being much less common.`-Increased awareness has led investigators to focus on SDAT and to search for means of identifying subjects in the less advanced stages, before the illness is complicated by effects of chronic debility and/or institutionalisation.Establishing presumptive diagnostic criteria without resorting to histologic study of the brain is an essential goal of clinical investigation. The importance of this goal is underscored by the difficulties inherent in distinguishing among the many disorders leading to brain failure3`and by the dearth of valid information on aetiology, natural history, pathophysiology, and therapy of SDAT. Concurrent needs include a reliable means of quantifying the degree of dementia9 and a comparison of the effects of healthy aging with those of SDAT. The Dementia Study Group of Washington University has met frequently for several years to discuss and investigate topics related to dementia.`0-17 The needs listed above led to the group to establish explicit clinical diagnostic criteria for SDAT and to initiate a longitudinal study of mild cases and healthy aging. In this paper is Address for reprint requests: L Berg, MD.,

Forty-three subjects with mild senile dementia of the Alzheimer type, diagnosed and staged by clinical research criteria, were studied with clinical, psychometric, EEG, visual evoked potential, and CT measures. During the 12 months following entry into the study, 21 subjects progressed to moderate or severe dementia, 21 remained mild, and one was lost to follow-up. Many of the clinical and psychometric measures of impairment were predictive of the progression to moderate or severe dementia. Electrophysiologic and CT measures were not. In a discriminant function analysis, the scores on two measures (the digit symbol subtest of the Wechsler Adult Intelligence Scale and an Aphasia Battery) correctly predicted the stage of dementia 1 year later in 95% of the subjects.