Language performances in dementia with Lewy bodies and Alzheimer's disease: A longitudinal comparative study of naming and fluency

BackgroundWhile language impairments are well-documented in Alzheimer's disease (AD), their longitudinal progression in dementia with Lewy bodies (DLB) remains poorly understood.ObjectiveTo compare four-year trajectories of naming and verbal fluency in DLB, AD, and healthy controls (HC), and to identify the cognitive correlates underlying naming performance over time.MethodsThis study included 111 participants (62 DLB, 26 AD, 23 HC) followed at baseline, 12, 24, and 48 months. Primary outcomes were naming (DO-80) and verbal fluency (letter/semantic) scores. Secondary assessments included verbal memory, executive, and visuospatial functions. Linear Mixed Models compared longitudinal trajectories, and Spearman correlations explored cognitive associations.ResultsA significant Visit x Group interaction (p < 0.001) revealed that naming remained stable in DLB (-1.15 points) and HC, whereas AD patients showed a steep decline (-7.77 points). In DLB, letter fluency remained stable over 48 months, while semantic fluency significantly decreased (p = 0.002). Conversely, AD patients deteriorated across all tasks. By month 48, DLB patients significantly outperformed AD patients in naming (p = 0.002) and semantic fluency (p = 0.015). Naming in DLB was positively and increasingly correlated with executive functions (Frontal Assessment Battery: rho 0.416 to 0.578) and Mini-Mental State Examination, whereas in AD, it was tied to episodic memory. No correlation was found with attentional fluctuations in DLB.ConclusionsThese findings highlight distinct language trajectories: naming abilities are relatively preserved in DLB compared to the global collapse in AD. This preservation in DLB appears increasingly dependent on executive control, underscoring the need for tailored, domain-specific interventions.