Cognitive reserve among highly intelligent older individuals makes
detection of early Alzheimer's disease (AD) difficult. We tested the
hypothesis that mild memory impairment determined by IQ-adjusted norms is
associated with single photon emission computed tomography (SPECT)
perfusion abnormality at baseline and predictive of future decline.
Twenty-three subjects with a Clinical Dementia Rating (CDR) score of 0,
were reclassified after scores were adjusted for IQ into two groups, 10 as
having mild memory impairments for ability (IQ-MI) and 13 as memory-normal
(IQ-MN). Subjects underwent cognitive and functional assessments at
baseline and annual follow-up for 3 years. Perfusion SPECT was acquired at
baseline. At follow-up, the IQ-MI subjects demonstrated decline in memory,
visuospatial processing, and phonemic fluency, and 6 of 10 had progressed
to a CDR of 0.5, while the IQ-MN subjects did not show decline. The IQ-MI
group had significantly lower perfusion than the IQ-MN group in
parietal/precuneus, temporal, and opercular frontal regions. In
contrast, higher perfusion was observed in IQ-MI compared with
IQ-MN in the left medial frontal and rostral anterior cingulate regions.
IQ-adjusted memory impairment in individuals with high cognitive reserve
is associated with baseline SPECT abnormality in a pattern consistent with
prodromal AD and predicts subsequent cognitive and functional decline.
(JINS, 2007, 13, 821–831.)