Abstract
A number of linguistic and cognitive deficits have been reported during the course of Alzheimer’s disease (AD) and its preceding stage of mild cognitive impairment (MCI), with some deficits appearing years before onset of clinical symptoms. It continues to be a critical task to identify tools that may serve as an early marker of pathology that are also reliably able to distinguish AD from normal ageing. Given the limited success of classic psychometric cognitive testing, a novel approach in assessment is warranted. A potentially sensitive assessment paradigm is discourse processing. The aim of this review was to synthesize original research studies investigating comprehension of discourse in AD and MCI, and to evaluate the potential of this paradigm as a promising avenue for further research. A literature search targeting studies with AD or MCI groups over 60 years of age was conducted in PubMed, Web of Science, and PsycINFO databases. Eight articles with good quality were included in the review. Six measures of discourse comprehension—naming latency, summary, lesson, main idea, proportion of inferential clauses, true/false questions—were identified. All eight studies reported significant deficits in discourse comprehension in AD and MCI groups on five of the six measures, when compared to cognitively healthy older adults. Mixed results were observed for associations with commonly used cognitive measures. Given the consistent findings for discourse comprehension measures across all studies, we strongly recommend further research on its early predictive potential, and discuss different avenues for research.
Highlights
The overarching goal of this review is to evaluate currently available research measuring macrostructural discourse comprehension in the course of Alzheimer’s disease (AD), and to assess the potential of a discourse comprehension paradigm as a novel approach in neuropsychological testing, in seeing what it may add to current testing practices
A total of eight articles were included in the review, which aimed to measure discourse comprehension at a macrolevel, in adults with Alzheimer’s disease or mild cognitive impairment (MCI)
Despite some variations in the methods and outcome measures across the eight studies included in the review, significant deficits in macrostructural discourse comprehension were observed in AD and MCI groups across all, but one, measures in all studies, in comparison with cognitively healthy older adults
Summary
As life expectancy continues to increase, the ageing population continues to grow in number, and so does the prevalence and incidence of age-related disorders. Dementia is one of the most common age-related disorders, and is a major cause of concern worldwide due to its untreatable nature. As of 2018, an estimated 50 million people worldwide live with dementia, with the number expected to be over 152 million by the year 2050 (Patterson 2018). (AD) is the most common type of dementia, accounting for an estimated 60% to 80% of the cases. It results in progressive cognitive and functional decline, which is irreversible, and begins before clinical onset of AD. The clinical manifestation of AD is preceded by a transitional stage of mild cognitive impairment (MCI), which has received considerable attention as a target stage for early detection and interventions
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