Simple topological task-based functional connectivity features predict longitudinal behavioral change of fluid reasoning in the RANN cohort

•Longitudinal change in task-based functional connectivity was investigated across the lifespan in the reference ability neural network (RANN) cohort.•Topological data analysis (TDA) was compared to whole-brain system segregation with respect to age-related decline.•TDA measure displayed age-related longitudinal decreases for fluid reasoning whereas system segregation displayed age-related longitudinal decreases in Memory, fluid Reasoning, and processing speed.•When investigating the link between connectivity and behavior, only the TDA measure significantly predicted longitudinal cognitive change in the fluid reasoning domain.•The longitudinal TDA measure mediated the effect of age on longitudinal change in cognition again for the fluid reasoning domain.