Supplementary Material for: Written Discourse Task Helps to Identify Progression from Mild Cognitive Impairment to Dementia

<b><i>Purpose:</i></b> We aimed to investigate: (1) the clinical, diagnostic value of a written discourse task, and (2) the relationship between executive functions and written discourse within the spectrum of individuals with mild cognitive impairment (MCI). <b><i>Method:</i></b> To determine whether written discourse performance predicts clinical course among individuals with MCI, we retrospectively classified individuals with MCI as converters (<i>N</i> = 26) who were later diagnosed with dementia or as a stable MCI group (<i>N</i> = 45). We quantified core word measures from written discourse samples obtained from the Cookie Theft picture description task. <b><i>Result:</i></b> Written discourse measures differentiated converters from the stable MCI group. Converters produced a fewer number of core words than the stable MCI group. A measure of executive function significantly predicted performance on the production of core words in written discourse for the converters. In a multivariable regression, production of core words remained the only explanatory variable closely associated with the progression to dementia in MCI. <b><i>Conclusion:</i></b> Written discourse tasks can predict the likelihood of MCI progressing to dementia, independently of recall and an executive function measure. Correlational results suggest that written discourse performance was associated with executive function as measured by the Trail Making Test. Our findings emphasize the usefulness of including written discourse tasks in language assessment batteries targeting preclinical dementia populations.