Cross-sectional versus longitudinal cognitive assessments for the diagnosis of symptomatic Alzheimer’s disease in adults with Down syndrome
Individuals with Down syndrome are at a high risk of developing the clinical symptoms of Alzheimer’s disease in old age due to the triplicating of chromosome 21. However, the clinical diagnosis of this disease is challenging, mainly due to the inherent intellectual disability.
Current clinical guidelines emphasize the use of longitudinal cognitive measures for the detection of symptomatic Alzheimer’s disease; which involves comparing an individual’s cognitive performance over time. Nonetheless, no studies have demonstrated that longitudinal cognitive assessment is more sensitive than cross-sectional measures, which refer to cognitive performance at a single time-point.
What have been done in this study?
Our main objective was to compare the diagnostic performance of cross-sectional and longitudinal cognitive assessments for the detection of Alzheimer’s disease in a cohort of 562 adults with Down syndrome.
What are the main results?
Our findings show that the diagnostic accuracy of cross-sectional neuropsychological measures exceeded that of longitudinal cognitive assessments at the 1- and 2-year intervals. Therefore, we suggest that, akin to the general population, population norms and cutoff points should be established for the correction of neuropsychological tests.
Relevance of the study
This is the first comparative study of the diagnostic performance of cross-sectional and longitudinal cognitive assessments for the detection of symptomatic Alzheimer’s disease in Down syndrome. Contrary to current clinical recommendations, we observed that neuropsychological assessments at a single time point have good diagnostic performance even in the early stages of the disease (prodromal phase).
These results may entail a paradigm shift in the way Alzheimer’s disease is diagnosed in this population, as it allows for early and accurate diagnosis and thus earlier intervention. On the other hand, our findings provide valuable information to define cognitive endpoints for clinical trials for Alzheimer’s disease specifically designed for individuals with Down syndrome.