Cognitive changes in memory precede those in praxis in aging persons with Down syndrome

Experimental tests of cognitive functions were developed and standardised to detect the onset and progression of the early stage of Alzheimer disease in persons with Down syndrome. The aim was to determine whether or not there was a specific sequence of cognitive changes over a 3-year period for the test measures. When compared with a young group (17–39 years of age at the start), an old group of persons with Down syndrome (40–58 years of age at the start) showed small but statistically significant changes over time suggestive of “pre-clinical signs” of dementia. When the data were sorted into 4 subgroups on the basis of age, a more detailed analysis revealed that the subgroup that was 50 years of age and older at the start showed changes in scores which were of a magnitude more clearly indicative of early dementia on the test measures. Deterioration in learning/memory functions began at a mean age of 54.2 years, followed later by deterioration in movement-related functions (praxis) at a mean age of 56.9 ...