Verbal fluency performance in normal adult population in Iran: Norms and Effects of age, education and gender

Objective: Verbal fluency is a cognitive function that can be easily assessed in bedside and provide useful data for clinical assessment of a variety of cognitive functions. We decided to provide a standardized test for the assessment of verbal fluency in Persian language, including both phonemic and semantic fluency subtests.  Method: First, three letters (P, D, and Sh) and three categories (animals, fruits, and objects of kitchen) were selected based on a pilot study and a panel of specialists. Then, we selected 500 Persian speaking participants (47.8% male) that were 18 to 65 years old via convenient sampling from general population. Participants were stratified according to age, gender, and education. They performed the verbal fluency test.  Results: The mean number of generated words in letter fluency and semantic fluency (±SD) were 8.3±4.1 and 18.0±5.5, respectively. Age, educational level, and mother tongue were associated with letter fluency. Semantic fluency was associated with age, gender, education level, and mother tongue. Conclusion: For a more reliable clinical assessment, we suggest to use all of the three letters and three semantic categories for each subject, calculate the mean of the produced words and compare them with the suggested cut-points provided for each subcategory. Age was negatively correlated with the number of generated words in letter fluency (r=-0.33; p<0.001) and semantic fluency tasks (r=-0.26; p<0.001). In letter fluency task, there was not a statistically significant difference between males and females according to the number of generated words (P=0.057). However, in semantic fluency, female participants generated more words (p=0.005). Mother tongue (Farsi) showed a significant effect both on letter fluency (t=5.55, p<0.001) and semantic fluency (t=9.41, p<0.001). Level of education had a significant association with both letter fluency (F=117.23, p<0.001) and semantic fluency (F=64.48, p<0.001).