Normal ageing in adults with Down's syndrome: a longitudinal study

Abstract

The ubiquitous presence of the neuropathology of Alzheimer disease (AD) in individuals with Down's syndrome (DS) over 40 years of age suggests that this group of people will exhibit a high prevalence of dementia of the Alzheimer type (DAT) as they age. The present study indicates that there is a clear discrepancy between the presumed presence of AD neuropathology and the clinical expression of DAT among older people with DS. In the first 6 years of a longitudinal study, the present authors compared 91 adults (31-63 years of age) with DS and mild or moderate mental retardation to 64 adults (31-76 years of age) with other forms of mental retardation (MR) on yearly measures of mental status, short- and long-term memory, speeded psychomotor function, and visuospatial organization. The results indicated that, over repeated testing on the verbal long-term memory test, younger participants with DS showed small increases in their scores, while older participants with DS showed very slight decreases. Overall performance scores on this test and a speeded psychomotor task were poorer for both diagnostic groups in individuals aged 50 years and older. The magnitude and type of these selective changes in performance were consistent with performance profiles observed in older healthy adults without mental retardation on tests measuring similar cognitive functions. Only four out of the 91 people with DS in the present sample showed changes in functioning that have led to a diagnosis of possi…