Dissociation in Age-Related Developmental Trajectories Between Phonetic Fluency and Semantic Fluency Tests: Analysis of Longitudinal Data From the Yakumo Study

Possible age-related differences in Phonemic Fluency Test (PFT) and Semantic Fluency Test (SFT) performance were examined by using longitudinal data of healthy older adults. The performance trajectories of 81 older adults in the 2 tests were analyzed for 11 years, from 65 to 75 years of age, via individually calculated linear regression coefficients. The results indicated that the PFT and SFT performance showed an age-related decline. However, the declining slope of the SFT was steeper than that of the PFT performance. These findings correspond with those of previous cross-sectional studies and suggest a future need to examine neurobiological substrates underlying the two domains of verbal fluency abilities.