Intraindividual Variability in Verbal Fluency Performance Is Moderated by and Predictive of Mild Cognitive Impairments

Objective: The current study was designed to achieve 2 primary objectives: (a) determine the moderating effect of mild cognitive impairments (MCI) on intraindividual variability in semantic and letter fluency performance taking into account longitudinal annual assessments; and (b) establish predictive utility for intraindividual variability in semantic and letter fluency performance as a risk factor of incident MCI. Methods: Participants were community-residing older adults (n = 514; M age = 75.89 ± 6.45; 55.1% female). Sixty participants were diagnosed with MCI at baseline and 50 developed incident MCI during the follow-up. We operationalized intraindividual variability as word generation slopes derived from 3 consecutive time intervals during the standard 1-min administration of both letter and semantic fluency tasks (i.e., 0-20 s, 21-40 s, and 41-60 s). Results: Linear mixed effects models revealed significant within task slope effects for semantic (estimate = −8.350; p < .0001; 95% confidence interval [CI] = −8.604, −8.095) and letter (estimate = −5.068; p < .0001; 95% CI [−5.268, −4.869]) fluency indicating that word generation declined over the course of both tasks. The two-way interactions of MCI × Slope were significant for semantic (estimate = 1.34; p = .001; 95% CI [0.551, 2.126]) and letter (estimate = 0.733; p = .020; 95% CI [0.116, 1.350]) fluency indicating attenuated slopes among MCI participants compared to controls taking into account repeated annual assessments. Cox proportional-hazards models revealed that attenuated word generation slope, at baseline, in semantic (hazard ratio [HR] = 2.063; p = .015; 95% = 1.149 to 3.702) but not letter (HR = 0.704; p = .243; 95% CI [0.391, 1.269]) fluency was associated with increased risk of incident MCI. Conclusion: Intraindividual variability in verbal fluency performance has clinical and predictive utility; it can be easily incorporated into testing batteries in clinical and research settings. General Scientific Summary Identifying older adults at risk of cognitive decline has important individual and public health implications. Here we demonstrated that a change in performance within a person during the course of a commonly used neuropsychological test predicted the risk of future cognitive decline in a cohort of community-residing older adults. The method used to assess the change in performance during the course of the task could be easily incorporated into standard testing procedures in both cl