When blood pressure rises, it strains the tiny blood vessels that keep brain cells alive, Koroshetz says.
"With every pulse of your heart, you are pushing blood into these very small blood vessels in the brain," he says. And when the heart pushes too hard, as it does when blood pressure is elevated, it can cause damage that can lead to a stroke.
At least two large studies have revealed an alarming trend among stroke patients, Koroshetz says.
"If you had a stroke, even a small stroke, your risk of dementia within the next two years was greatly magnified," he says. "So there's something about having a stroke that drives a lot of the processes that give rise to dementia."
The evidence is clearest for a type of dementia called vascular dementia. It occurs when something blocks or reduces the flow of blood to brain cells.
But high blood pressure also appears to increase a person's risk of developing Alzheimer's disease, which is associated with the accumulation of plaques and tangles in the brain.
If people knew about the link between dementia and high blood pressure, they might be more inclined to do something about it, Koroshetz says.
"Only about 50 percent of people who have hypertension are actually treated," he says. "So I think there's a lot to be said for trying to get high blood pressure under control."
Koroshetz's campaign is getting some help from the Alzheimer's Association.
The group will present new research on blood pressure and Alzheimer's at its annual scientific meeting in Chicago, which starts July 22. And the group is encouraging people to control high blood pressure.
"The good news is that we can control blood pressure now," says Maria Carrillo, the group's chief science officer. "We can do that with exercise, with lifestyle, with healthy eating and also with medications."
Koroshetz is using all of these approaches. And he says other people with high blood pressure should follow his lead.