Background. While neuropathological studies indicate a
high risk for Alzheimer's disease in adults
with Down's syndrome, neuropsychological studies suggest a lower prevalence
of dementia. In this
study, cognitive deterioration in adults with Down's syndrome was
examined prospectively over
4 years to establish rates and profiles of cognitive deterioration.
Methods. Fifty-seven people with Down's syndrome aged
30 years or older were assessed using a
battery of neuropsychological tests on five occasions across 50 months.
Assessments of domains of
cognitive function known to change with the onset of Alzheimer related
dementia were employed.
These included tests of learning, memory, orientation, agnosia, apraxia
and aphasia. The individual
growth trajectory methodology was used to analyse change over time.
Results. Severe cognitive deterioration, such as acquired,
apraxia and agnosia, was evident in 28·3%
of those aged over 30 and a higher prevalence of these impairments was
associated with older age.
The rate of cognitive deterioration also increased with age and degree
of pre-existing cognitive
impairment. Additionally, deterioration in memory, learning and orientation
acquisition of aphasia, agnosia and apraxia.
Conclusions. The prevalence of cognitive impairments consistent
with the presence of Alzheimer's
disease is lower than that suggested by neuropathological studies. The
pattern of the acquisition of
cognitive impairments in adults with Down's syndrome is similar to
that seen in individuals with
Alzheimer's disease who do not have Down's syndrome.