HI My Father Is 70, His Is In Good Physical

HI My father is 70, his is in good physical condition and very active (having been a PTI in the army), however he is saying that his he feels dizzy and his head feels foggy. I asked him how long he has been feeling like this and he said a few weeks. I have been researching symptoms of a stroke I can't find anywhere if they can start this far out from a stroke actually occurring.