Meta-analysis of Controlled Oral Word Association Test (COWAT) FAS performance in amnestic mild cognitive impairment and cognitively unimpaired older adults

Findings from several studies have shown that amnestic mild cognitive impairment (aMCI) older adults have significantly lower performance on phonemic fluency tasks relative to cognitively unimpaired (CU) older adults. These findings suggest that nonmemory domains, such as executive function, are impacted in aMCI. As Alzheimer's disease (AD) research has shifted toward identifying and characterizing preclinical AD, there is a need to identify subtle but significant cognitive changes that are below the threshold for clinical impairment. The aim of this meta-analysis was to examine phonemic fluency differences between aMCI and CU older adults. Data from 18 studies were included in this analysis that found that aMCI individuals' phonemic fluency performance was approximately seven points lower than CU individuals (Delta = -7.31, 95% CI [-9.10, -5.52], z = -8.01, p < 0.001), which represents a medium effect size of (g = 0.61, 95% CI [0.46, 0.76], z = 7.90, p < 0.001). Normative conversion of the aMCI groups' raw scores showed that all were in the normal range of performance. The findings of this meta-analysis demonstrate that significant subclinical deficits in phonemic fluency can be present in aMCI. This should prompt greater use of phonemic fluency tasks in outcome measures for observational and intervention studies.