Mild Cognitive Impairments Moderate the Effect of Time on Verbal Fluency Performance

Objectives: Mild cognitive impairments (MCI) is a transitional state in aging associated with increased risk of incident dementia. The current study investigated whether MCI status moderated the effect of time on word generation during verbal fluency tasks. Specifically, the objective was to determine whether MCI status had differential effects on initial automatic or latter more effortful retrieval processes of fluency tasks. Methods: Participants were community residing older adults enrolled in a longitudinal cohort study. Of the 408 participants, 353 were normal (age = 76.06 +/- 6.61; %female = 57.8) and 55 were diagnosed with MCI (age = 78.62 +/- 7.00; %female = 52.7). Phonemic and category fluency were each administered for 60 s, but performance was recorded at three consecutive 20-s intervals (0-20s [T1], 21-40s [T2], 41-60s [T3]. Separate linear mixed effects models for each fluency task were used to determine the effects of group, time, and their interaction on word generation. Results: In both fluency tasks, word generation declined as a function of time. Individuals with MCI generated fewer words compared to controls during the first 20s of phonemic (beta = -1.56; p < .001; d = 0.28) and category fluency (beta = -1.85; p < .001; d = 0.37). Group by time interactions revealed that individuals with MCI demonstrated attenuated declines in word generation from the first to the second and third time intervals of both phonemic ([T1 vs. T2] beta = 2.17, p = .001; d = 0.41; [T1 vs. T3] beta = 2.28, p = .001; d = 0.45) and category ([T1 vs. T2] beta = 2.22, p = .002; d = 0.50; [T1 vs. T3] beta = 3.16, p < .001; d = 0.71) fluency. Conclusions: Early automatic retrieval processes in verbal fluency tasks are compromised in MCI.