Worried about Alzheimer’s disease? You’re in the majority. A national survey says it’s North America’s most feared disease. While nothing, so far, can guarantee you’ll prevent or reverse the plaques, tangles and nerve-cell death that characterize Alzheimer’s, it turns out keeping the blood vessels in your brain healthy may cut your risk of brain dysfunction by a lot. There’s more and more evidence from academic and scientific brain centers around the world that a few simple steps can protect your cognitive powers and slash your risk for Alzheimer’s.