It's fairly common for people to be aware that there's something wrong with them early in the course of the disease. It's a painful thing to acknowledge. Other people are completely unaware. Dementia is particularly difficult for individuals who remain acutely and painfully aware of difficulties as their impairment worsens. In addition to the memory and thinking difficulties there are a whole host of behavioral and other psychiatric problems in Alzheimer's.
People tend to be depressed.
The risk of depression is related to the level of awareness of the deficits. In addition to depression people develop symptoms of aggressiveness, often directed at caregivers. They may develop inappropriate sexual behaviors and other behaviors that are completely out of character. They may become crude and profane in language. These are often the problems that bring people to Sheppard Pratt for treatment.