Can lexical properties of words produced on a semantic fluency task distinguish older adults with cognitive decline from older adults with stable cognitive scores?

INTRODUCTION Deficits in semantic fluency are commonly observed across many types of dementia. However, deficits in semantic fluency are not always representative of a decline in language skills. Prior studies have suggested that the examination of the lexical properties of words produced on semantic fluency tasks may reveal disruptions in discrete cognitive processes that could assist in the detection of specific types of dementia.

Method

The mean word frequency, age of acquisition, and phonological neighborhood size of items generated on a semantic fluency task (fruits and vegetables) were compared between a sample of individuals with mild cognitive impairment or dementia (cognitively impaired, N = 65) and a sample of healthy older adults with normal cognition who were cognitively stable over an average of 5 years following initial assessment (cognitively stable, N = 72). Relations of these variables to scores on tests of language, executive functioning, and processing speed were also explored.

Results

After controlling for age and education, the cognitively impaired group produced words of higher mean word frequency and lower mean age of acquisition than the cognitively stable group. Mean phonological neighborhood displayed the opposite pattern to expectations, with the cognitively stable group generating words with more phonological neighbors. Relations of evaluated word properties to tests of varied cognitive domains were explored in the overall sample, with mixed results.

Conclusions

Word properties of items generated on a semantic fluency task differed between cognitively impaired and cognitively stable groups. Future studies should investigate word properties of semantic fluency responses in the context of severity of cognitive impairment, thoroughly examine susceptibility to sociocultural factors, evaluate if findings are consistent across semantic fluency tasks, and explore ability to offer incremental validity for differential diagnosis and early detection over total scores alone.