Does the meaning of neurocognitive change change with age?

Abstract

Significant declines in longitudinal comparisons of neurocognitive performance are seldom evident until adults are in their 60s or older, but relatively little is known about the existence, or nature, of age-related changes at earlier periods in adulthood. The current research was designed to address this issue by examining characteristics of change in measures from 12 neuropsychological and cognitive tests at different periods in adulthood. Although change was largely positive for adults under about 55 years of age and frequently negative for adults at older ages, the reliabilities of the changes in the neuropsychological and cognitive variables were similar at all ages. Furthermore, there were few systematic relations of age on the reliability-adjusted correlations between the changes in composite scores representing different abilities. These results imply that although neurocognitive declines may not be apparent at young ages because of positive retest effects or other factors, at least in some respects longitudinal changes may have nearly the same meaning across all of adulthood.

Figure 1

Mean longitudinal change (second score minus first score) in individual variables in first-occasion z-score units for 12 overlapping age groups.

Figure 2

Coefficient alpha estimates of the reliability of longitudinal changes in individual variables for 12 overlapping age groups.

Figure 3

(A) Mean longitudinal change in first-occasion z-score units for composite ability scores for 12 overlapping age groups. (B) Coefficient alpha estimates of the reliability of longitudinal changes in composite ability scores for 12 overlapping age groups. (C) Reliability-adjusted correlations between changes in composite scores for 12 overlapping age groups.