Speech and language characteristics differentiate Alzheimer's disease and dementia with Lewy bodies

Abstract

Introduction: Early differential diagnosis of Alzheimer's disease (AD) and dementia with Lewy bodies (DLB) is important, but it remains challenging. Different profiles of speech and language impairments between AD and DLB have been suggested, but direct comparisons have not been investigated.

Methods: We collected speech responses from 121 older adults comprising AD, DLB, and cognitively normal (CN) groups and investigated their acoustic, prosodic, and linguistic features.

Results: The AD group showed larger differences from the CN group than the DLB group in linguistic features, while the DLB group showed larger differences in prosodic and acoustic features. Machine-learning classifiers using these speech features achieved 87.0% accuracy for AD versus CN, 93.2% for DLB versus CN, and 87.4% for AD versus DLB.

Discussion: Our findings indicate the discriminative differences in speech features in AD and DLB and the feasibility of using these features in combination as a screening tool for identifying/differentiating AD and DLB.

Keywords: acoustic; digital health; language impairment; linguistic; machine learning; natural language processing; prosodic; spontaneous speech.

FIGURE 1

Differences in the linguistic, acoustic, and prosodic features between three clinical diagnostic groups: Alzheimer's disease (AD) patients, dementia with Lewy bodies (DLB) patients, and cognitively normal (CN) individuals. (A) Graphs of linguistic (upper left), acoustic (upper right), and prosodic (lower left and right) features. Boxes indicate the 25th (Q1) and 75th (Q3) percentiles. Whiskers indicate the upper and lower adjacent values that are most extreme within Q3+1.5 (Q3–Q1) and Q1–1.5 (Q3–Q1), respectively. The line and diamond in each box represent the median and mean, respectively. Dots outside of the box represent outliers. Horizontal bars indicate significant differences (Tukey‐Kramer test: *P < 0.05, **P < 0.01, ***P < 0.001). (B) Radar chart comparing the linguistic, acoustic, and prosodic features of the AD, DLB, and CN groups, scaled according to Z‐scores derived from the CN group's means and standard deviations.

FIGURE 2

Differences in acoustic features (upper: jitter; lower: shimmer) based on clinical diagnosis (cognitively normal [CN], Alzheimer's disease [AD], dementia with Lewy bodies [DLB]) and disease stages (mild cognitive impairment [MCI], dementia). Boxes indicate the 25th (Q1) and 75th (Q3) percentiles. Whiskers indicate the upper and lower adjacent values that are most extreme within Q3+1.5 (Q3–Q1) and Q1–1.5 (Q3–Q1), respectively. The line and diamond in each box represent the median and mean, respectively. Dots outside of the box represent outliers.