NORMAL AGING IN ADULTS WITH DOWNS-SYNDROME - A LONGITUDINAL-STUDY

The ubiquitous presence of the neuropathology of Alzheimer disease (AD ) in individuals with Down's syndrome (DS) over 40 years of age sugges ts that this group of people will exhibit a high prevalence of dementi a 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 aut hors compared 91 adults (31-63 years of age) with DS and mild or moder ate mental retardation to 64 adults (31-76 years of age) with other fo rms of mental retardation (MR) on yearly measures of mental status, sh ort- and long-term memory, speeded psychomotor function, and visuospat ial 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 sho wed very slight decreases. Overall performance scores on this test and a speeded psychomotor task were poorer for bath diagnostic groups in individuals aged 50 years and older. The magnitude and type of these s elective changes in performance were consistent with performance profi les observed in older healthy adults without mental retardation on tes ts measuring similar cognitive functions. Only four out of the 91 peop le with DS in the present sample showed changes in functioning that ha ve led to a diagnosis of possible DAT, and in these individuals, alter native causes of performance declines were concurrently present (e.g. thyroid dysfunctional). These findings indicate that some age-associat ed changes in functioning are related to 'normal' but probably precoci ous ageing among adults with DS. Furthermore, these findings suggest t hat adults with DS and mild or moderate mental retardation may be at l ower risk for dementia during their fourth and fifth decades of life t han previous studies have suggested.