Dementia: Definition, Causes and Symptoms

Dementia: Definition, Causes and Symptoms

Dementia is a general term that includes specific disorders such as Alzheimer's disease, Vascular or Multi-infarct dementia, Pseudodementia, and others. Dementia is defined as a loss in at least two areas of complex behavior, such as language, memory, visual and spatial abilities, or judgment, that significantly interferes with a person's daily activities.

Dementia affects over 4 million Americans, is the 4th major cause of death, and costs society $100 billion annually.


Of the number of neurological disorders that can cause progressive memory loss in aging, Alzheimer's disease (AD) accounts for about 50%, Vascular dementia and Diffuse Lewy Body dementia about 10-20%, and depression about 1-5%. The other causes result from metabolic, infectious, traumatic, inflammatory, and mass lesion disorders.

Symptoms and Course of AD

The initial symptom of Alzheimer's Disease is almost always a persistent problem with remembering recently learned information. The course is characterized by a gradual or stepwise decline in memory, orientation, visual and spatial abilities, naming, fluency, comprehension, and judgment, difficulty in making calculations and handling money, and finally loss of control over body functions. Alzheimer's Disease affects all socioeconomic levels of all societies.

What Should I Look For?

Although dementia affects multiple areas of mental and functional performance, it may start out only affecting one area. In general, the more complex mental abilities a task requires, the more likely it is to be affected by a dementing illness early on. This means you should consider what it is that you do that requires complex mental abilities. For many people, having greater difficulty performing complex mental tasks at their job may be the first symptom. For example, a business manager may note greater difficulty coordinating the various departments and employees under his or her control. Persons whose jobs do not require complex mental skills may notice the first symptoms balancing their checkbook, remembering to pay bills on time, remembering what they read in the newspaper that day.

REMEMBER, everyone has areas they are weak in. That is not dementia. It is when you start to lose a mental ability that you previously could do that you should investigate further.

Short Term Memory

An early feature of most dementias is the impairment of short term memory or the inability to recall information you just learned. The reason that complex mental abilities become affected early on is that they often rely on a functioning short term memory system. Some examples of such mental abilities are:

Normal and Abnormal Short Term Memory

For many of us as we age, it is more difficult to freely recall these sorts of short term memories. Our current understanding is that this is a normal feature of aging. However, it is also true of normal aging that we can recall the short term memory if given the right cue or hint. Some stimulus that triggers recalling the event or fact such as a smell, a color, a word, a sound, or a sight provides the "energy" needed to activate the recall of the memory. This cued form of short term memory is called recognition memory, and is generally preserved with aging. Greater difficulty with recognition memory should be investigated further.

Procedural Skills & Learning New Procedures are Often Preserved

Short term memory is different from learning how to ride a bike, to sew, to do crossword puzzles, to bowl, to sing a song from "rote memory", to play bridge or other card games, to play tennis, or any other skill that takes thousands of repetitions before it is learned. This latter form of learning is sometimes called Procedural Motor Learning, and is preserved in many types of dementia, including Alzheimer's disease. This is valuable because many of the things we enjoy doing in life involve learning procedural motor skills, and these activities are preserved in many dementias. In fact, persons with some types of dementia, including Alzheimer's, can learn new skills when the motor learning task is properly structured!

Examples of the kinds of things some of our Alzheimer's patients can do well into the moderate to severe stages of the dementia are:

Inheritance of Alzheimer's:Is the Diagnosis Correct?

If someone has Alzheimer's disease in your family, the first thing you must know is whether the diagnosis is correct. Alzheimer's has become a waste-basket term for diagnosing persons with dementia without doing a proper evaluation. If one uses the standard guidelines from the NINCDS-ADRDA committee for diagnosing probable and possible Alzheimer's Disease, a 90% agreement between the clinical and autopsy diagnosis can be obtained. Unless these criteria have been applied or an autopsy diagnosis has confirmed AD, one can not be sure that the diagnosis is correct.

Will I Definitely Get Alzheimer's if Someone in my Family Has It?

No, but your risks may be greater. Recent research has shown that several genes are associated with increased risks.

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