Prevalence, Causes & Types of Dementia: Dementia Series, Part 3

Video transcription
Dementia (part 1), unfortunately, is extremely common. 47 million people around the world are affected,1 and 1 in 10 people will develop dementia at some point in their lives.2 The nature of dementia makes it the most significant cause of disability in people ages 65 and older, with an enormous impact on a person, their family and their caregivers.

Dementia is not one thing — it’s a group of symptoms (part 2) that can have many different underlying causes. Depending on the cause, some dementias may be reversible.3 That is why finding the root cause of dementia by going to the doctor and getting a comprehensive evaluation is critical.

Dementia types

Dementia is classified into two types, based on the part of the brain and the corresponding neurological functions that are affected, cortical dementia and subcortical dementia.

Cortical dementia

In cortical dementia, the part of the brain that’s damaged is the cortex, which is critical for higher level, abstract thinking. In this case, problems with memory and language are the main symptoms.

Subcortical dementia

In subcortical dementia, the deep brain structures beneath the cortex are affected — mental processing speed and initiative for new activities are the main deficits. It is also possible for both parts of the brain to be affected. Unfortunately, dementia is complicated.

Dementia causes

The most common cause of dementia is neurological disease that alters brain cells or structures. As you may have guessed, the most common of these is Alzheimer’s disease, which accounts for over half of dementia cases.4

There are other neurological diseases — frontotemporal lobar degeneration, Parkinson’s, Huntington’s, MS and others — that, like Alzheimer’s, can cause dementia, but these are more rare.5

Not all causes of dementia are diseases. Vascular dementia can occur after a stroke in the brain.6 Chronic alcohol or drug use,7 traumatic brain injury8 as a result of a car accident or sports-related concussion, or brain infections such as meningitis or HIV/AIDS can cause dementia symptoms.9 Typically these dementias cannot be treated or cured.

Occasionally, dementia can be caused by deficiencies in vitamins or hormones, and those dementias can be reversed when the problem is corrected.10

In the next video, we’ll talk about what happens in the brain during dementia, risk factors and prevention.


  1. “Dementia.” World Health Organization. April 2016. Web. 18 May 2017. Retrieved from
  2. Alzheimer’s Association. (n.d.).2017 Alzheimer’s Disease Facts and Figures. Retrieved from
  3. “There Are Dementia Symptoms That Are Treatable.” 3 February 2014. Web. 18 May 2017. Retrieved from
  4. “2015 Alzheimer’s disease facts and figures.”Alzheimer’s Association. March 2015. Web. 18 May 2017. Retrieved from
  5. “The Dementias: Hope Through Research.” National Institute on Aging. 26 April 2017. Web. 18 May 2017. Retrieved from
  6. Alzheimer’s Association. (n.d.).2017 Alzheimer’s & Dementia. Retrieved from
  7. “Dementia associated with alcohol and other drug use.” National Center for Biotechnology Information. 2005. Web. 18 May 2017. Retrieved from
  8. Alzheimer’s Association. (n.d.).2017 Alzheimer’s & Dementia. Retrieved from
  9. “Neurological Complications of HIV.” Johns Hopkins Medicine. Web. 18 May 2017. Retrieved from,46/
  10. “Dementia due to metabolic causes.” Medline Plus. 9 May 2017. Web. 18 May 2017. Retrieved from

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