Sure. Via: https://www.nia.nih.gov/health/alzheimers-disease-fact-sheet#treating": Alzheimer’s disease is an irreversible, progressive brain disorder".
Alzheimer’s is a very complicated topic for multiple reasons, including but not limited to the fact that there are other conditions that have characteristics similar to those of Alzheimer’s, but because they don’t meet all of a certain number of criteria, these conditions are simply called “dementia” or another, related name.
From the same source: " Other dementias include Lewy body dementia, frontotemporal disorders, and vascular dementia. It is common for people to have mixed dementia—a combination of two or more disorders, at least one of which is dementia. For example, some people have both Alzheimer’s disease and vascular dementia."
And from: https://www.mayoclinic.org/diseases-conditions/alzheimers-disease/expert-answers/alzheimers-disease/faq-20057881: (Can excercise prevent Alzheimer’s disease): “Possibly. Exercise has many known benefits, including reducing the risk of cardiovascular disease and diabetes, strengthening the bones and muscles, and reducing stress.”
Note that the answer is not “yes” but rather “possibly”. No one can prove that anything 100% guarantees that it “prevents” Alzheimer’s just like no one can 100% prove that anything prevents cancer. But data exist that show correlations.