Abstract
Objective
Late-life depression (LLD) has been associated with cognitive impairments in domains such as memory, processing speed, and executive functions (e.g., initiation). However, it is unclear whether or not LLD is associated with language fluency difficulties that are often seen in some forms of dementia. Broadly, letter fluency is often observed to be associated with frontal deficits while category fluency is thought to be linked to temporal lobe dysfunction. Both tests are commonly used to assess language in older adults. The current meta-analysis examined potential differences between letter and category fluency in LLD and the robustness of previous findings in this population.
Data Selection
Investigators searched eight databases including PubMed and PsycINFO using terms such as “neuropsychol*,” “late-life,” and “depression.” Studies were excluded if participants were diagnosed with severe mental illness, neurological or other medical conditions that impact neurocognition.
Data Synthesis
Independent coders extracted data from 27 studies (k = 10 letter fluency, k = 17 semantic fluency). The effect size for semantic fluency was g = 0.64 (p < 0.001) with significant heterogeneity I² = 73.53% (Q = 60.45, df = 16, p < 0.001). The effect size for letter fluency was g = 0.49 (p < 0.001) also with significant heterogeneity I² = 52.08% (Q = 18.78, df = 9, p < 0.027).
Conclusions
Depressed individuals exhibited poorer performance on both category and letter fluency when compared to controls. This may indicate that depressed elderly individuals have difficulty with initiating verbal responses regardless of whether these responses rely on semantic networks or executive control.
Continued methodological imprecisions, nontransparency, and misinterpretation in a meta-analysis of semantic fluency in schizophrenia: a comment on “Corrigendum to: Semantic memory impairment across the schizophrenia continuum: a meta-analysis of category fluency performance” by Tan et al.
