Dementia isn't a specific disease. Instead, dementia describes a group of symptoms affecting memory, thinking and social abilities severely enough to interfere with daily functioning. Alzheimer's disease is the most common cause of a progressive dementia in older adults, but there are a number of other causes of dementia including alcohol abuse and heart and/or vascular disease. Dementia can involve both cognitive and psychological changes.

Cognitive changes: Memory loss, difficulty communicating or finding words, trouble reasoning or problem-solving, difficulty handling complex tasks, trouble planning and organizing, trouble with coordination and motor functions, and confusion and disorientation
Psychological changes: Personality changes, depression, anxiety, inappropriate behaviors, paranoia, and agitation