From verbal fluency to naturalistic speech: a scoping review of language correlates of loneliness and social isolation in older adults.

Introduction: Population aging poses significant societal and health challenges, with loneliness and social isolation (L/SI) recognized as pressing public health concerns. While social isolation refers to an objective lack of social contacts, loneliness reflects the subjective perception that one's social needs are not being met. Although L/SI have been associated with an increased risk of dementia and global cognitive decline, their relationship with language functioning remains largely underexplored. Given the central role of language in social interaction, examining this relationship is particularly relevant. Methods: Following PRISMA-ScR guidelines, we conducted a scoping review to a) map the language domains and measures used in the literature, and b) synthesize evidence on the association between L/SI and language functioning in older adults. Web of Science, PubMed, and Scopus were searched without temporal restrictions using terms related to language, L/SI, and aging. Eligible studies included older adults (≥60 years) and examined the association between at least one language measure and one indicator of L/SI. Results: Thirty-four studies met the inclusion criteria. Considerable heterogeneity was observed in both language and social-disconnection measures. The literature focused primarily on verbal fluency tasks, with comparatively less attention devoted to lexical retrieval, discourse production, semantic processing, and speech-derived computational markers. Associations between L/SI and verbal fluency were suggestive but not robust after covariate adjustment, whereas discourse- and speech-derived markers emerged as promising, albeit methodologically underdeveloped, sources of evidence. Discussion: Current evidence suggests L/SI may be associated with language functioning in older adults. However, the literature remains conceptually and methodologically heterogeneous, highlighting the need for more systematic, comprehensive, and methodologically consistent research in this area.