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Published on: June 25, 2019
'Normal' semantic-phonemic fluency discrepancy in Alzheimer's disease? A meta-analytic study
Keith R Laws1, Amy Duncan, Tim M Gale
1School of Psychology, University of Hertfordshire, Hatfield, UK. k.laws@herts.ac.uk
Summary
Alzheimer's disease (AD) patients show greater impairment in semantic fluency than phonemic fluency. However, the semantic-phonemic fluency discrepancy is not unique to AD and may be an exaggerated normal tendency.
Area of Science:
- Neuroscience
- Cognitive Psychology
- Gerontology
Background:
- Alzheimer's disease (AD) is a progressive neurodegenerative disorder.
- Language impairments, including semantic and phonemic fluency deficits, are common in AD.
- The discrepancy between semantic and phonemic fluency is often cited as a key characteristic of AD.
Purpose of the Study:
- To quantitatively assess the relative impairment of semantic and phonemic fluency in Alzheimer's disease (AD) patients.
- To investigate factors influencing fluency performance in AD.
- To examine whether the semantic-phonemic fluency discrepancy is a unique marker of AD.
Main Methods:
- A meta-analysis of 135 studies comparing 6000 AD patients with 6057 healthy controls.
- Calculation of effect sizes for semantic fluency, phonemic fluency, and picture naming.
- Meta-regression analyses to explore moderator variables (e.g., patient demographics, dementia severity, education).
- Analysis of semantic-phonemic discrepancy scores in studies measuring both fluency types.
Main Results:
- Semantic fluency showed a significantly larger effect size of impairment (d=2.10) compared to phonemic fluency (d=1.46) and picture naming (d=1.54) in AD patients.
- Meta-regression revealed that higher proportions of female patients and less severe dementia were associated with better phonemic fluency.
- Increased patient education unexpectedly correlated with worse semantic fluency.
- The effect size for semantic-phonemic discrepancy scores did not differ between AD patients and controls and was not influenced by moderator variables.
Conclusions:
- Semantic fluency is more severely affected than phonemic fluency in Alzheimer's disease (AD).
- Factors like sex, dementia severity, and education level influence fluency performance in AD.
- The semantic-phonemic fluency discrepancy is not a specific marker for AD and may represent an exaggeration of normal cognitive tendencies.
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