Did You Know

Heredity plays a role in causing certain forms of dementia; however, in most types of dementia, many other factors are also involved. It is, therefore, very difficult to predict who will get it and who will not. Read more about each type of dementia to learn how much of a role heredity plays for that type.

In most cases, dementia is not caused by a person's behaviors or actions. Instead, most dementia develops as a result of either a biological cause or a physical event in the body.

Neurodegenerative Causes of Dementia

Neurodegeneration is the most common biological cause of dementia and often leads to Alzheimer's disease. Neurodegeneration is the process where brain cells (neurons) break down and die. These dying brain cells cause a permanent and progressive decrease in mental and physical function over time. Types of dementia that result from neurodegeneration include:

Cerebrovascular Causes of Dementia

Damage to blood vessels in the brain, or cerebrovascular damage, is a common biological cause of dementia. It includes strokes and/or narrowing of the blood vessels supplying the brain. Localized areas of the brain are destroyed (so-called "infarcts") from not getting enough blood supply. Many of the same factors that cause heart disease also cause cerebrovascular disease. The type of dementia that results from cerebrovascular disease is:

Infection-Related Dementia

Infection can also cause dementia. Viruses, bacteria, or parasites can destroy brain cells and dementia can result in some cases -- usually in later stages of severe infections. Common types of dementia caused by infection include:

Toxic and Metabolic Causes of Dementia

Dementia can also result from a chemical imbalance in the body caused by either a toxin (e.g. drugs), malnutrition, or other biological conditions, such as metabolic disorders. This form of dementia includes:

Traumatic Causes of Dementia

Serious injuries and concussions to the head and brain can cause dementia. This category includes:

Resources
Source: 
Alzheimer's Society (United Kingdom)
Description: 
This web page briefly describes common causes of the different types of dementia and links to fact sheets for each type. A link for rarer causes of dementia is also included.
Source: 
eMedicine from WebMD
Description: 
This article discusses the many causes of dementia, including different diseases and infections, strokes, head injuries, drugs, and nutritional deficiencies. It also describes irreversible conditions and treatable conditions separately.
Source: 
WebMD
Description: 
Description of the role of heredity in Alzheimer's