Genetic/Environmental Architecture and Stability of Executive Functions in Midlife

Research on executive functions (EFs) has suggested that a general factor underlies performance across a number of EF tasks and domains. This Common EF factor is highly stable in adolescence through young adulthood, correlates... [ view full abstract ]

Research on executive functions (EFs) has suggested that a general factor underlies performance across a number of EF tasks and domains. This Common EF factor is highly stable in adolescence through young adulthood, correlates with other cognitive abilities, and is explained largely by genetic influences. However, little is known about Common EF beyond young adulthood. We examined data from 1,464 middle-aged twins in the Vietnam Era Twin Study of Aging who completed seven neuropsychological measures of EFs at two time points (mean age 56 and 62), as well as measures of general cognitive ability and processing speed. Confirmatory factor analysis indicated that Common EF (at age 56) was moderately heritable (a²=.46), with additional evidence for shared environmental influences (c²=.41) and nonshared environmental influences (e²=.13). Common EF (at age 56) was moderately associated with higher general cognitive ability, measured both in early adulthood (age 20) and in midlife (age 56), and faster processing speed in midlife (age 56). These correlations were driven by shared genetic influences. After accounting for practice effects, there was a large mean-level performance decline in Common EF (d = -.60) between age 56 and 62, but individual differences in Common EF remained highly stable over time (r=.97), with genetic and shared environmental influences showing perfect overlap (r_a=1.0, r_c=1.0). Finally, we also identified a Working Memory Span-specific factor that captured variance in span tasks above and beyond Common EF. This span-specific factor was highly heritable at age 56 (a² = .81), and also showed strong stability at the level of genetic and shared environmental influences (r_a=1.0, r_c=1.0). These results suggest that the latent factor structure of EF is similar in midlife as in earlier ages, and that individual differences in EFs continue to show strong stability throughout midlife even as mean-level performance declines substantially.