High blood pressure, diabetes and smoking can damage blood vessels throughout the body. Lead investigator Dr. Josef Coresh said the findings reinforce the importance of controlling vascular risk factors from about age 45 onward. The researchers emphasised that the study does not prove these risk factors directly caused dementia because it was observational. Despite these limitations, the findings fit with many previous studies showing that healthy blood vessels are essential for a healthy brain. Randomized prevention studies will be needed to confirm how much reducing these risk factors can delay dementia.