From the National Institute on Aging
As Alzheimer’s disease progresses, the person with the disease may have hallucinations, delusions, or paranoia. During a hallucination, the person sees, hears, smells, tastes, or feels something that isn’t there. He or she also may have delusions—false beliefs that the person thinks are real.
Paranoia is a type of delusion in which a person may believe—without a good reason—that others are mean, lying, unfair, or “out to get me.” He or she may become suspicious, fearful, or jealous of people.