WAIS Information Subtest as an indicator of crystallized cognitive abilities and brain reserve among highly educated older adults: A three-year longitudinal study.

The Wechsler Adult Intelligence Scale-Third Edition (WAIS-III) Information Subtest (IS) is known as a neuropsychological "Hold" test that is relatively resistant to decline with aging. We administered neuropsychological tests among highly educated healthy older adults once a year for three subsequent years. Results showed highly stable performances on the IS across years (Mean Z score: T0 = 1.39, SD = 0.60; T1 = 1.37, SD = 0.77; T2 = 1.50, SD = 0.66; T3 = 1.48, SD = 0.66), that were significantly higher than zero (T0: t = 12.08; T1: t = 9.29; T2: t = 11.71; T3: t = 11.68; for all, p < 0.0001). In contrast, other neuropsychological tests showed differences in performance across time; some performances significantly declined (Rey Osterrieth Complex Figure test-copy, Rey-Auditory Verbal Learning Test, and Montreal Cognitive Assessment test [MoCA]), whereas others were improved, possibly due to practice effects (Rey Osterrieth Complex Figure test- delayed, Rey-Auditory Verbal Learning Test- delayed, and Trail Making Test- part A). Correlation with whole brain volumetric analysis revealed a positive correlation between gray matter volumes and IS scores (r = 0.46, p < 0.05) even when controlling for age and education (partial correlations: r = 0.43; r = 0.45, for both p < 0.05). No significant correlations were found between gray matter and other test scores. Therefore, the WAIS-III Information subtest appears to be an adequate neuropsychological measurement of crystallized ability in highly educated older adults and may be considered as a proxy measure of brain reserve.