Semantic and Phonemic Verbal Fluency Discrepancy in Mild Cognitive Impairment: Potential Predictor of Progression to Alzheimer's Disease

ObjectivesTo assess the utility of verbal fluency discrepancy scores in predicting progression to Alzheimer's disease (AD) in a cohort of individuals with mild cognitive impairment (MCI). DesignCase control. SettingCases identified from new referrals to a memory clinic and controls identified from The Irish Longitudinal Study on Ageing. ParticipantsOf 308 individuals with MCI at baseline identified from consecutive referrals to a memory clinic and compared at with age-, sex-, and education-matched controls (n=302), 161 completed 2 years of follow-up or progressed to AD during the study period. MeasurementsVerbal fluency discrepancy (semantic-phonemic fluency) scores at baseline were calculated for each participant. Each case was followed with repeated neuropsychological measurements, and multidisciplinary consensus diagnosis was recorded. ResultsMean discrepancy score for those who progressed to AD (2.7) was significantly lower than for those who retained a MCI diagnosis (4.8) and normal controls (7.7) (p<.001). Logistic regression revealed that, for each unit decrease in discrepancy score at baseline, the odds of progressing to AD were 9% greater. (Exp(B)=1.09, p=.02) ConclusionIndividuals with MCI have less of a semantic advantage than those without MCI. Those with MCI presenting with a phonemic advantage at initial assessment warrant close follow-up and a high index of suspicion for progression to AD.