Vascular risk and A beta interact to reduce cortical thickness in AD vulnerable brain regions

Objective: The objective of this study was to define whether vascular risk factors interact with beta-amyloid (Ab) in producing changes in brain structure that could underlie the increased risk of Alzheimer disease (AD).

Methods: Sixty-six cognitively normal and mildly impaired older individuals with a wide range of vascular risk factors were included in this study. The presence of Ab was assessed using [C-11] Pittsburgh compound B-PET imaging, and cortical thickness was measured using 3-tesla MRI. Vascular risk was measured with the Framingham Coronary Risk Profile Index.

Results: Individuals with high levels of vascular risk factors have thinner frontotemporal cortex independent of Ab. These frontotemporal regions are also affected in individuals with Ab deposition, but the latter show additional thinning in parietal cortices. Ab and vascular risk were found to interact in posterior (especially in parietal) brain regions, where Ab has its greatest effect. In this way, the negative effect of Ab in posterior regions is increased by the presence of vascular risk.

Conclusion: Ab and vascular risk interact to enhance cortical thinning in posterior brain regions that are particularly vulnerable to AD. These findings give insight concerning the mechanisms whereby vascular risk increases the likelihood of developing AD and supports the therapeutic intervention of controlling vascular risk for the prevention of AD.