Cognitive and linguistic impairments in adults with Down syndrome and Alzheimer's disease: a systematic review

OBJECTIVES: To explore the cognitive and linguistic impairments associated with Alzheimer's disease (AD) in individuals with Down syndrome (DS), identify gaps in current research, and propose directions for future investigation. METHODS: A systematic review following PRISMA guidelines was conducted using PubMed, Scopus, and Web of Science from database inception to May 2026. Studies examining cognitive and linguistic impairments in adults with DS and AD were included. Findings were synthesized across cognition and memory, language and communication, and functional and social impact domains. RESULTS: Fourteen studies met the inclusion criteria. Significant impairments in episodic memory, executive functioning, and attention were consistently identified as early markers of AD-related decline in adults with DS. Linguistic deficits, particularly receptive language impairments, semantic verbal fluency decline, naming difficulties, and short-term memory alterations, were also frequently reported. Functional consequences included reduced independence in daily activities and increasing communicative limitations. Across studies, assessment tools primarily emphasized cognitive domains, while language impairments remained comparatively underexplored. CONCLUSION: DS-associated AD requires integrated assessment approaches addressing cognitive, linguistic, communicative, and functional domains. Future research should prioritize longitudinal studies and population-sensitive assessment tools to improve early detection and individualized interventions.