Is it dementia or is it Alzheimer's?

by matt bridgman

I have been asked this question many times. What is the difference between dementia and Alzheimer's disease? Read more to find out. 

Dementia is a syndrome. Alzheimer's is a disease. 

Dementia is the term used to refer to a condition where someone has a significant decline in at least two areas of cognitive ability (refer back to my post on cognition for a description of those areas), to the point that they are no longer capable of completing daily tasks independently.

Dementia involves basically two criteria:
1) a significant drop in at least two areas of cognition (such as memory, language, attention, or reasoning ability)
AND
2) that drop in cognition is severe enough that the person has to depend on other people for daily tasks or responsibilities. 

For example, if someone has a worsening of their memory and language skills, to the point that they are no longer capable of managing their own finances, or managing their own medications, then they would be considered to have dementia. 

(One exception would be if the worsening of cognition is determined to be reversible, such as because of medication side effects. That would then be considered a delirium - a sudden and temporary confusion - not dementia).

The term "dementia" therefore says nothing at all about what exactly is causing the change in cognition. 

Alzheimer's disease, then, is a disease that causes or leads to dementia. Alzheimer's disease starts (in most cases) by damaging the memory center of the brain (the hippocampus) and then progresses to damage other areas of the brain, causing impairments in memory and other areas of thinking, to the point that those individuals become unable to manage various daily activities. 

Alzheimer's disease is the most common cause of dementia, but numerous other diseases also lead to dementia. Cerebrovascular disease (caused by either a large stroke, multiple smaller strokes, or a long history of issues like uncontrolled diabetes, high blood pressure, and high cholesterol), Lewy body disease, frontotemporal degeneration, and Parkinson's disease are other causes of dementia.

I cannot stop there, however, as the term "dementia" has fairly recently been replaced/updated. What we used to refer to as dementia (that which I have described above) is now called Major Neurocognitive Disorder. 

Major Neurocognitive Disorder (formerly dementia) is distinguished from Mild Neurocognitive Disorder. Mild Neurocognitive Disorder is the midpoint between cognitive changes of healthy aging, and Major Neurocognitive Disorder. If changes in cognition are viewed on a scale, with one end of the scale representing the mild cognitive changes typical of healthy aging, and the other end of the scale representing cognitive changes severe enough to be causing loss of independence (that would be Major Neurocognitive Disorder), then Mild Neurocognitive Disorder is the middle of the scale. 

Mild Neurocognitive Disorder = changes in cognitive functioning that are more than what would be expected just from healthy aging, but the individual is still living and functioning independently. "Changes in cognitive functioning that are more than what would be expected just from healthy aging" is something that is determined by neuropsychological testing: an individual's current cognitive test scores are compared to those of healthy individuals in their age range (while also accounting for individual differences such as education history and work history). 

Although individuals with Mild Neurocognitive Disorder are, by definition, still living and functioning independently, they are typically making more mistakes than they used to, and they are usually having to work harder to compensate for the memory changes. 

This post is a very brief introduction to these conditions, and is certainly not enough information for anyone to self-diagnose. A comprehensive neuropsychological evaluation is the only way to accurately distinguish between cognitive changes of healthy aging versus Mild Neurocognitive Disorder versus Major Neurocognitive Disorder. Accurate diagnosis (through a neuropsychological evaluation) requires an assessment of many factors, such as developmental history, education history, family history, medical history, occupational history, and others. Objective measurement of cognition is also required, and the results of such measurement/testing must be interpreted in the context of an individual's age and the aforementioned factors. If you are concerned that you or a loved one may be showing signs of any of these conditions, talk with your family doctor to see if a neuropsychological evaluation would be appropriate. 

Check out the Resources/Links page for links to websites containing further information about dementia/Major and Minor Neurocognitive Disorder, and neurodegenerative diseases such as Alzheimer's and Lewy Body disease.