IOW, those with Alzheimer's have done better when they are more physically active. Obviously this is because vasodialation (opening of blood vessels) increases with exercise.
My step father had a bad case. He often reported feelings of "surging blood" in his upper body (neck, shoulders, head) which most-likely was related to what is being discussed in the article.
He did not exercise much. His only activity late in life was walking his dog. Once he could no longer do that, his mental condition declined dramatically and he passed away.