Semantic and phonemic advantages in Alzheimer's disease and behavioral variant-frontotemporal dementia: Insights from the Fluency Type Index

Background: Phonemic and semantic verbal fluency tasks are cognitive measures that engage both executive functioning and language. Objective: Exploring the prevalence of phonemic and semantic advantages (PAs; SAs) in patients with dementia due to Alzheimer's disease and behavioral variant-frontotemporal dementia (ADD; bvFTD) by means of the Fluency Type Index (FTI), and to examine, in these populations, its association with clinical variables. Methods: ADD (N = 113) and bvFTD (N = 38) patients and healthy controls (HCs, N = 87), were administered phonemic and semantic fluency tests. The FTI was computed using demographically adjusted scores as follows: SVF-PVF/SVF + PVF. Negative values suggest a PA and positive ones suggest a SA. Bidirectional tolerance limits were computed on HCs' FTI values to set the thresholds for defining both a PA and a SA. In patients, correlational analyses were run to test the association between FTI values and disease duration (in months) and severity (i.e., Mini-Mental State Examination, MMSE). Results: In the ADD cohort, an almost equal number of patients displayed a PA (11%) and a SA (10%). In the bvFTD group, 11% of patients presented with a SA, while a PA was less frequent (5%). FTI classification distributions did not differ between these two groups (p = 0.615). In ADD patients, but not in bvFTD ones, the FTI was negatively related to disease duration (p = 0.009). No associations were detected with the MMSE. Conclusions: Both PAs and SAs might be common to both ADD and bvFTD patients; however, in ADD patients, PAs might reflect a longer disease duration and a more severe cognitive involvement.