It depends on the person and how useful the information is, and your “delivery” of it. If they are asking questions about why they are forgetting things and you think it will ease their mind to tell them, and that they really want to know, then explain to them what you are noticing. However, you don’t want it to tell it to them every day, and constantly give them examples. As things progress they do not need to be reminded of it. It is better to reassure them that you are there for them and will help them navigate their daily needs.