Some investigators have postulated that cerebrovascular risk factor increase the risk of AD, while others do not support that view. There are data that suggest that if you have AD and then have a stroke the disease onset may occur earlier. These are questions that people have that are currently unresolved. Obviously having multiple strokes and AD is not good and is certainly worse than having one disease. So whether cerebrovascular disease has a causal relationship to AD or whether cerebrovascular disease and AD simply share risk factors is unclear right now.
Silent strokes occur in a good portion of the population.
We don't know whether that triggers something or is even important. Currently vascular biology of the brain is extremely important and not fully worked out in terms of the relationship to degenerative disease. We know a lot more, the methods are better, the imaging is helping us sort out who is going to get AD and who is not. The genetics are very exciting, and AD is a major public health problem that will only increase in the immediate future. There will be more tools to ask more and more specific questions.