Timed executive functions and white matter in aging with and without cardiovascular risk factors.

The present article reviews recent studies of 'healthy aging' with and without cardiovascular risk factors and accompanying white matter changes. Specifically, the relationship between white matter hyperintensities (WMH) and various cognitive functions, in particular executive functions (EF), was subjected to meta-analysis. The results of this analysis indicate that WMH induce a decrease in performance on timed EF tests, while the more basic cognitive abilities (e.g. short-term memory and vocabulary) remained relatively intact. Interestingly, the performance on untimed EF tasks was uniformly unrelated to WMH. This pattern of cognitive dysfunction was observed equally in the 'healthy aged' and the cardiovascular group. These findings suggest that an important distinction exists between untimed and timed EF tests, and that this distinction should be taken into account when interpreting the results of such tests.