Cognitive and functional decline in the stage previous to the diagnosis of Alzheimer's disease

Introduction: The decline in the phase prior to diagnosis of Alzheimer's disease (AD) is not well known, although this knowledge is necessary to evaluate the efficiency of new drugs that can influence in disease course prior to diagnosis. Objective: To contribute to better knowledge of the decline prior to diagnosis, we have investigated the cognitive and functional deterioration for 2-3 years before the probable AD diagnosis was established. Patients and methods: We compared results obtained by 17 control subjects and 27 patients at the time of diagnosis of a probable AD with results obtained 2-3 years before (interval of 27.7+4 months). We compared memory functions (logical, recognition, learning and autobiographical memory), naming, visual and visuospatial gnosis, visuoconstructive praxis, verbal fluency and the Mini-Mental State Examination (MMSE), Informant Questionnaire and Blessed's Scale scores. Results: Performance of control subjects did not change. AD patients showed a significant decline in scores, except for verbal fluency. In order of importance, cognitive decline was more marked in scores of learning memory, visuospatial gnosis, autobiographical memory and visuoconstructive praxis. Conclussions: Decline prior to diagnosis of AD is characterized by an important learning memory impairment. Deterioration of visuospatial gnosis and visuoconstructive praxis is greater than deterioration of MMSE and Informant Questionnaire scores.