Neuropsychological evaluation of adults with Down's syndrome: patterns of selective impairment in non-demented old adults.

A battery of neuropsychological tests, developed to study patterns of age-related differences in adults with Down's syndrome (DS), was administered to 10 DS adults over age 35 and 19 younger DS adults. Although all adults with DS are reported to develop the neuropathological changes of Alzheimer's disease by the fourth decade of life, only four of the 10 old DS adults were judged to have dementia based on clinical criteria. Demented old DS adults had global neuropsychological deficits, as indicated by significant differences on all functions tested except some simple language functions. In contrast, non-demented old adults had a selective pattern of neuropsychological reductions relative to young adults. Ability to form new long-term memories and visuospatial construction were consistently diminished, whereas immediate memory span and language were not. The global mental decline observed in demented adults suggests a stage of disease progression that corresponds to severe dementia in premorbidly normal adults with dementia of the Alzheimer type (DAT). The prominent long-term memory impairment with selective reductions of nonmemory functions in non-demented adults suggests a correspondence to early and intermediate DAT.