Analysis of spontaneous, conversational speech in dementia of Alzheimer type: Evaluation of an objective technique for analysing lexical performance

Spontaneous, conversational speech in probable dementia of Alzheimer type ( DAT) participants and healthy older controls was analysed using eight lingu istic measures. These were evaluated for their usefulness in discriminating between healthy and demented individuals. The measures were; noun rate, pr onoun rate, verb rate, adjective rate, clause-like semantic unit rate tall per 100 words), including three lexical richness measures; type token ratio (TTR), Brunet's Index (W) and Honore's statistic (R). Results suggest that these measures offer a sensitive method of assessing spontaneous speech ou tput in DAT. Comparison between DAT and healthy older participants demonstr ates that these measures discriminate well between these groups. This metho d shows promise as a diagnostic and prognostic tool, and as a measure for u se in clinical trials. Further validation in a large sample of patient vers us control 'norms' in addition to evaluation in other types of dementia is considered.