Background: We compared differences in intelligence and memory function between normal elderly Japanese subjects with more years of education and those with fewer years of education. We also investigated clinical and neuropsychological factors that are strongly correlated with memory function.
Methods: There were 118 normal elderly subjects who underwent the Mini-Mental State Examination, Wechsler Adult Intelligence Scale, 3rd edition (WAIS-III), and Wechsler Memory Scale Revised. Subjects with at least 13 years of education were categorized as the H group, and those with 12 years of education or less were categorized as the L group.
Results: Age and Mini-Mental State Examination scores were not significantly different between the two groups. On the WAIS-III, there were significant differences between the two groups in Verbal IQ and Full Scale IQ. On the Wechsler Memory Scale Revised, there were significant differences between the two groups in Visual Memory, General Memory, and Delayed Recall. Correlation coefficients between memory function and the other factors demonstrated significant but weak correlations between years of education and General Memory (R = 0.22) and between years of education and Delayed Recall (R = 0.20). Strong correlations were found between Verbal IQ and Verbal Memory (R = 0.45), between Verbal IQ and General Memory (R = 0.49), between Full Scale IQ and General Memory (R = 0.50) and between Full Scale IQ and Delayed Recall (R = 0.48).
Conclusions: In normal elderly Japanese subjects, years of education weakly correlated with memory function while Verbal IQ, Full Scale IQ and Verbal Comprehension on WAIS-III had stronger correlations with memory function. Verbal IQ and Verbal Comprehension on WAIS-III were found to be insusceptible to the cognitive decline characteristic of Alzheimer's disease or amnestic mild cognitive impairment. Therefore, verbal intelligence, as measured by Verbal IQ and Verbal Comprehension, may be the most useful factor for inferring premorbid memory function in Alzheimer's disease or amnestic mild cognitive impairment patients.