Alzheimer's Disease and Other Types of Dementia

Alzheimer's Disease
More than 5 million Americans have Alzheimer’s disease, the most common form of dementia. Alzheimer’s accounts for 60 to 80 percent of all dementia cases. That includes 11 percent of those age 65 and older and one-third of those 85 and older. The disease also impacts more than 15 million family members, friends and caregivers.

Dementia is a general term for the loss of memory and other cognitive abilities serious enough to interfere with daily life.

Other types of dementia:


  • Vascular dementia is a decline in thinking skills caused by conditions that block or reduce blood flow to the brain, depriving brain cells of vital oxygen and nutrients. These changes sometimes occur suddenly following strokes that block major brain blood vessels. It is widely considered the second most common cause of dementia after Alzheimer’s disease.
  • Mixed dementia is a condition in which abnormalities characteristic of more than one type of dementia occur simultaneously. Symptoms may vary, depending on the types of brain changes involved and the brain regions affected, and may be similar to or even indistinguishable from those of Alzheimer’s or another dementia.
  • Parkinson’s disease dementia is an impairment in thinking and reasoning that many people with Parkinson’s disease eventually develop. As brain changes gradually spread, they often begin to affect mental functions, including memory and the ability to pay attention, make sound judgments and plan the steps needed to complete a task.
  • Dementia with Lewy bodies is a type of progressive dementia that leads to a decline in thinking, reasoning and independent function due to abnormal microscopic deposits that damage brain cells.
  • Huntington’s disease dementia is a progressive brain disorder caused by a defective gene. It causes changes in the central area of the brain, which affect movement, mood and thinking skills.
  • Creutzfeldt-Jakob disease is the most common human form of a group of rare, fatal brain disorders known as prion diseases. Misfolded prion protein destroys brain cells, resulting in damage that leads to rapid decline in thinking and reasoning as well as involuntary muscle movements, confusion, difficulty walking and mood changes.
  • Frontotemporal dementia (FTD) is a group of disorders caused by progressive cell degeneration in the brain’s frontal lobes (the areas behind the forehead) or its temporal lobes (the regions behind the ears).
  • Normal pressure hydrocephalus is a brain disorder in which excess cerebrospinal fluid accumulates in the brain’s ventricles, causing thinking and reasoning problems, difficulty walking and loss of bladder control.
  • Down syndrome dementia develops in people born with extra genetic material from chromosome 21, one of the 23 human chromosomes. As individuals with Down syndrome age, they have a greatly increased risk of developing a type of dementia that’s either the same as or very similar to Alzheimer’s disease.
  • Korsakoff syndrome is a chronic memory disorder caused by severe deficiency of thiamine (vitamin B-1). It is most commonly caused by alcohol misuse, but certain other conditions can also cause the syndrome.
  • Posterior cortical atrophy (PCA) is the gradual and progressive degeneration of the outer layer of the brain (the cortex) located in the back of the head (posterior). It is not known whether PCA is a unique disease or a possible variant form of Alzheimer’s disease.