Age-Related Differences in Resting-State Functional Connectivity Predict Specific Patterns of Speech Disfluency

Fluent speech production remains largely preserved across adulthood, yet subtle disruptions such as pauses, repetitions, and revisions become more common with age. These disfluencies may reflect underlying cognitive and neural changes that accompany aging, particularly in executive function (EF) and large-scale brain network organization. In this study, we examined whether EF and resting-state functional connectivity (RSFC) independently or jointly explained age-related differences in naturalistic speech disfluencies in an adult lifespan sample (n = 252, ages 20-81 years). RSFC was used to assess network segregation within three systems implicated in language and cognitive control: language network, default mode network (DMN), and multiple demand (MD) network. These task-independent connectivity patterns provide insight into how the brain's functional architecture impacts speech production and its age-related vulnerabilities. Our findings indicate that age was associated with increased rates of specific disfluency subtypes, such as unfilled pauses, repetitions, and revisions, as well as lower EF and lower language, MD, and DMN network segregation. Although increasing age was associated with lower EF, EF performance did not predict disfluencies or mediate their age-related increase. In contrast, higher DMN segregation predicted lower overall disfluencies, repetitions, and revisions. Age moderated the relationship between DMN segregation and repetitions, with a significant association only in younger and middle-aged adults, suggesting weaker brain-behavior relationships at older ages. DMN segregation also partially mediated the relationship between age and revisions. These findings suggest that while EF relates to planning-related disruptions, changes in functional brain organization may more directly contribute to age-related increases in self-monitoring disfluencies.