Cognitive change in older women using a computerised battery: a longitudinal quantitative genetic twin study

Abstract

Cognitive performance is known to change over age 45, especially processing speed. Studies to date indicate that change in performance with ageing is largely environmentally mediated, with little contribution from genetics. We estimated the heritability of a longitudinal battery of computerised cognitive tests including speed measures, using a classical twin design. 324 (127 MZ, 197 DZ) female twins, aged 43-73 at baseline testing, were followed-up after 10 years, using seven measures of the Cambridge Automated Neuropsychological Test battery, four of which were measures of response latency (speed). Results were analysed using univariate and bivariate structural equation modelling. Heritability of longitudinal change was found in 5 of the 7 tests, ranging from 21 to 41%. The genetic aetiology was remarkably stable. The first principle component of change was strongly associated with age (p < 0.001) and heritable at 47% (27-62%). While estimates for heritability increased in all measures over time compared to baseline, these increases were statistically non-significant. This computerised battery showed significant heritability of age-related change in cognition. Focus on this form of change may aid the search for genetic pathways involved in normal and pre-morbid cognitive ageing.

Fig. 1

Study participants

Fig. 2

Relationship between Age and ARC factor score. y-axis: first principle component of factor analysis of all the change scores adjusted for baseline performance. Scores below 1 indicate declining function over 10 years. x-axis: age at second time point

Fig. 3

Cross sectional heritability estimates for each cognitive measure. Best fitting model heritability point estimates for each of the tasks and 95 % confidence intervals in the two waves of testing. The best models were CE for PAL errors, RTIS or SWM between errors in 1999