Speech-based machine learning for detecting neuropsychiatric symptoms in Alzheimer's disease

Abstract

Background

Neuropsychiatric symptoms (NPS) are common in Alzheimer's disease (AD) and mild cognitive impairment (MCI), yet their detection relies on subjective assessments. Speech features offer a promising objective biomarker for NPS, reflecting emotional and cognitive states. However, existing studies are limited in terms of scale and duration.

Objective

This study aims to characterize acoustic features associated with NPS in early cognitive decline using Automated Assessment Model-Mini-Mental State Examination framework, and to evaluate machine learning classifiers for identifying indicators of NPS.

Methods

Speech data from 647 clinically diagnosed AD or MCI patients were collected and split into training and test sets in a 6:4 ratio. The training set was used for feature selection and model development, while test set was used for performance evaluation. The Synthetic Minority Over-Sampling Technique was applied to address class imbalance. Twelve machine learning models were trained to classify NPS categories. The best-performing models were evaluated, and SHapley Additive exPlanations (SHAP) were used to analyze feature importance.

Results

The ExtraTrees model outperformed the others in identifying patterns associated with NPS categories, with cross-validated AUCs ranging from 0.869 to 0.901. SHAP revealed spectral_entropy_std and kurtosis_energy as key features across multiple NPS categories.

Conclusions

This study demonstrates that short speech samples obtained during the MMSE can identify acoustic patterns associated with NPS in clinically diagnosed AD and MCI using machine learning. Given the single-center design and absence of external validation, model outputs should be interpreted as directional signals to raise clinical awareness rather than as definitive diagnostic determinations.