Dementia Learning Center

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What is Dementia?

Dementia is a decline in cognitive function. It may affect memory, thinking, language, judgment, and behavior. To be considered dementia, mental impairment must affect at least two brain functions. It may also cause personality changes.

Dementia is not a disease. It may be caused by a variety of illnesses or injuries. Mental impairment may range from mild to severe. Some dementias are progressive, which means they get worse over time. Some dementias are treatable or even reversible. Some experts restrict the term dementia to irreversible mental deterioration.

What Causes Dementia?

Dementia can be caused by degeneration of neurons  (brain cells), or by disturbances in other body systems that affect how neurons function.

Several conditions can cause dementia, including diseases of the brain. The most common such causes are Alzheimer’s disease and vascular dementia.

Neurodegenerative means that neurons gradually degenerate (cease to function or function inappropriately and eventually die). This impacts the neuron-to-neuron connections, called synapses, which are how messages are passed along in your brain. This “disconnect” can result in a range of dysfunction.

Some of the more common causes of dementia include:

Neurodegenerative Diseases

People with dementia have declines in brain function that are significant enough to interfere with their relationships and daily routine. Doctors diagnose dementia when two or more functions are affected, such as memory and judgment. Many disorders can cause dementia. Some can be reversed, but others progress.

Other Causes of Dementia

Dementia may also be caused by

  • structural brain disorders
    • normal-pressure hydrocephalus (increased pressure on the brain due to the buildup of cerebrospinal fluid)
    • subdural hematoma (a collection of blood on the surface of the brain)
  • metabolic disorders
    • hypothyroidism
    • vitamin B-12 deficiency
    • kidney and liver disorders
  • toxins, such as lead

Some of these dementias may be reversible. This is one of the many reasons why it is important to see your doctor and get a medical workup as soon as symptoms develop.

Isn’t Forgetfulness a Normal Part of Aging?

It’s absolutely normal to forget things once in a while. Memory loss by itself does not mean you have dementia. However, there is a difference between occasional forgetfulness and forgetfulness that is cause for serious concern.

Potential red flags for dementia include:

  • forgetting who someone is
  • forgetting how to do common tasks (such as how to use the telephone or find your way home)
  • Inability to comprehend and/or retain information that has been clearly provided

Seek medical attention if you experience any of the above.

Getting lost in familiar settings (driving to the supermarket, for example), is often one of the first signs of dementia.

How Common Is Dementia?

The Merck Manual states that approximately five percent of people aged 65 to 74 years and 40 percent of people older than 85 years have some form of dementia.

The number of people diagnosed with and/or living with dementia is increasing. This is at least in part due to increasing life expectancy. By 2030, the size of the population 65 years of age and older in the U.S. will have increased from 37 million people (in 2006) to an estimated 71.5 million, according to the U.S. Census Bureau.

What Research is Being Done?

Scientists all over the world are working hard to gain a better understanding of the many different aspects of dementia. This might help to develop preventive measures (such as a vaccine), improved early detection diagnostic tools, better and longer-lasting treatments, and even cures.

For example, a vaccine known as a bapineuzumab jab is currently in its final phase of testing. Though it cannot cure dementia or related disorders, this vaccine has been shown to prevent, and in some cases reverse, the buildup of amyloid plaques in the brain. Amyloid plaques—which are the hallmark of Alzheimer’s disease—are dense, mostly insoluble (not dissolvable) clumps of protein fragments that deposit a highly damaging gunky substance outside and around the brain’s nerve cells.

Scientists are also investigating genetic factors, various neurotransmitters, the role of inflammation, factors that influence programmed cell death in the brain, the roles of tau (a protein found in neurons of the central nervous system), and the possible roles of oxidative stress (i.e., chemical reactions that can damage proteins, DNA, and lipids/fats inside cells) in the development of dementia. Such research can help doctors and scientists better understand what causes dementia, and in turn, how best to treat and possibly prevent the disorder.

There is also increasing evidence that lifestyle factors, such as getting regular exercise and maintaining social connections, may be effective ways to decrease the risk of developing dementia.

Content licensed from:

Written by: Wendy Leonard, MPH
Published on Jul 15, 2014
Medically reviewed on Jul 15, 2014 by Kenneth R. Hirsch, MD

This feature is for informational purposes only and should not be used to replace the care and information received from your health care provider. Please consult a health care professional with any health concerns you may have.
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