TYPOLOGY OF ALZHEIMERS-DISEASE - FINDINGS FROM CERAD DATA

To identify heterogeneity in Alzheimer's disease (AD) we analyzed clin ical and neuropsychological data obtained from the first 718 AD patien ts submitted to the Consortium to Establish a Registry for Alzheimer's Disease (CERAD). These patients, who met stringent exclusion criteria , were entered by 23 tertiary US medical centers and had the advantage s of uniform evaluation, substantial size and reduction in selection b iases reflecting investigator interests. A Grade of Membership (GoM) a nalysis was used. GoM, based in fuzzy set theory, identifies the under lying pure types in the data. GoM recognizes that individuals need not fall crisply into a particular type, but that their characteristics m ay fit different pure types to different extents. Clinical and neurops ychological data obtained at entry were analyzed. Six clinical pure ty pes were identified: AD with parkinsonism; AD with depressive symptoma tology; AD with mild language problems (parkinsonism and depressive sy mptoms absent); AD presenting with impaired cognitive status and probl ems performing instrumental activities of daily living; late onset, mi ld AD; late onset AD of long duration, severe at entry and with additi onal chronic disease present. Five neuropsychological pure types were identified. They differed primarily in level of performance of the mea sures examined. No notable relationships between the clinical and neur opsychological pure types were found. Additional pure types may be pre sent (e.g. familial AD), but cannot be identified in the absence of in formation in the data base. It is clear, however, that in a group of A D patients meeting strict criteria, heterogeneity of disease is presen t.