Cerebrovascular risk factors do not contribute to genetic variance of cognitive function: the ERF study

Impaired cognition in later life may result from Alzheimer's disease-related pathology, but also from vascular pathology. We studied to what extent vascular risk explained heritability of cognition in 780 individuals, related in one extended pedigree in a genetically isolated population, in the ERF study. Heritability was estimated using variance components modelling (SOLAR). Univariate analyses included models with and without vascular disease; bivariate analyses included both cognitive and vascular traits, such as blood pressure, serum glucose or lipids. Heritability for immediate and delayed recall, recognition, semantic fluency, Trail making B and Stroop tests was significant, with estimates from 0.16 to 0.36. Vascular factors did not affect cognitive functions, except immediate recall and the Stroop test. Heritability estimates did not change significantly when adjusted for vascular disease. We found no genetic correlation between cognition and vascular traits. Therefore, in this population vascular disease is mildly associated with cognitive dysfunction, and in those with vascular disease, the underlying genetic risk factors are not likely to account for the genetic variation in cognition at adult age.