Multimodal assessment of the impact of cognitive decline on language processing in older adults: A systematic review

Cognitive decline significantly compromises the quality of life in older adults, with language impairment serving as a critical early marker. Despite the increasing adoption of multimodal methods, existing reviews in this domain suffer from methodological limitations and a narrow scope. To address these gaps, this PRISMA-compliant systematic review synthesizes 15 studies (January 2000—May 2025) evaluating language processing in cognitive decline via multimodal approaches, integrating narrative synthesis with supplemental case analysis. The synthesized findings reveal that firstly, normal cognitive aging primarily compromises pragmatic processing and language recognition, while paradoxically enhancing spatial contributions to narrative macrostructure. Secondly, pathological cognitive decline encompasses two main types. Neurodegenerative diseases (AD, PD, MCI, PCA, PPA) broadly impair linguistic processing at all levels and modalities, affecting spoken and written discourse and extending to pragmatic markers. Post-stroke semantic aphasia presents a distinct profile characterized by inflexible conceptual application for unconventional objects, poor inhibition of semantically related distractors, and impaired suppression of strong concept-distractor associations; however, these patients’ object use improves with verbal and pictorial cues under stricter task conditions. Thirdly, multimodal methods, which integrate multiple modalities through two main channels have emerged as an effective approach with strong methodological potential: they may offer higher sensitivity and accuracy, and certain modality combinations may prove both cost-effective and resource-efficient. This review synthesizes the current research landscape on impaired language functions arising from different types of cognitive decline among older adults and delineates future directions in this field, including incorporating diverse data dimensions, employing longitudinal designs to elucidate temporal dynamics and causal relationships, and leveraging the strengths of multimodal approaches to address the limitations of conventional methods and enhance efficacy.