Dementia is a collection of symptoms characterized by cognitive problems – deficits in thinking, memory, reasoning, judgment, language, communication, and awareness. Dementia can also include psychological symptoms such as behavior, personality, and mood changes, as well as psychotic symptoms such as hallucinations and delusions. There are many causes of dementia. Knowing the type of dementia someone has helps doctors prescribe effective treatments and better predict how the disease will progress.
Alzheimer’s disease is the leading cause of dementia, accounting for 60 to 80 percent of cases. Other causes of dementia can include vascular dementia, dementia with Lewy bodies, Parkinson’s disease dementia, Huntington’s disease, mixed dementia, frontotemporal dementia, Creutzfeldt-Jakob (mad cow) disease, normal pressure hydrocephalus, and Wernicke-Korsakoff syndrome. Diagnosing which type of dementia someone has can be a complex process that may take years.
Alzheimer’s is typed by the age of onset.
Most people with Alzheimer’s have late-onset disease that develops after age 65. Nearly all cases of late-onset Alzheimer’s begin with memory issues.
Also called familial Alzheimer’s disease, or FAD, early-onset Alzheimer’s develops before age 65 in approximately 5 percent of people. Onset is usually in the 30s, 40s, or 50s. In early-onset Alzheimer’s, the earliest symptoms are more likely to be apraxia – a movement disorder that makes it difficult to perform voluntary actions – and vision changes such as loss of depth perception, peripheral vision, perceiving color or contrast, or spatial awareness of objects.