Reduced Cluster Switching in Category Fluency Reveals Cognitive Decline: A Longitudinal Study

Impairments in semantic fluency tasks are well-established in Alzheimer’s disease (AD). These are apparent both in quantitative measures, namely total number of items produced, and qualititative measures, namely the frequency with which AD patients switch between semantic clusters (e.g., from farm animals to African animals). Similar deficits have been seen in quantitative output of individuals who will go on to develop AD or who have been diagnosed with mild cognitive impairment (MCI). However, less research has examined qualitative aspects of fluency performance in these populations. We assessed the fluency performance over time of twelve healthy elderly who went on to be diagnosed with MCI. Over a seven-year period, declines were seen in qualitative measures, specifically the number of cluster switches, but not in total output. The finding that switching between clusters on a semantic fluency task begins to decline up to seven years before diagnosis with MCI indicates that performance on this task may be an important predictor of future cognitive decline in healthy elderly adults.