Dementia is a general term that is often misunderstood. Dementia refers to mental deterioration to the point that one can no longer do higher level mental tasks like doing a checkbook, using a computer, or preparing a meal. In more severe forms of dementia, one may no longer be able to tend to personal needs such as bathing, toileting, or changing clothes.

In other words, dementia refers to mental decline where one can no longer function independently (i.e., needs at least some level of external care). Dementia refers to the severity of the mental deterioration. It is not a state of being.

Dementia is caused by a loss of skills (i.e., brain function). There are many possible causes of dementia. For example, many who develop a progressive form of dementia have a heavy burden of amyloid plaques and tau tangles. When this is the cause of the decline the condition is referred to as Alzheimer’s disease. In short, dementia is the general term for decline and Alzheimer’s disease is the cause of the decline.

There are many other causes that can produce dementias. For example, when strokes cause the decline, the diagnosis would be vascular dementia. When a head injury causes the decline, the diagnosis would be dementia due to traumatic brain injury.

If the frontal lobes (the part of the brain that plans, makes judgments, interacts in socially appropriate ways, expresses oneself) decline, the diagnosis would be a frontotemporal dementia. Progressive loss of expressive language is diagnosed as a semantic dementia. There is a dementia sometimes associated with Parkinson’s disease.

There is another rather common dementia caused by Lewy bodies called diffuse Lewy body disease. These conditions (as well as others) are all irreversible declines in ability. Some of the conditions are progressive (meaning they get worse over time) whereas others may be develop suddenly then stabilize over time (such as a stroke or a brain injury).

We often hear of so called “treatable dementias.” This is a poor choice of words. The term dementia should refer to irreversible conditions. There are some medical conditions that may cause temporary mental deterioration. With appropriate treatment, there is a recovery to normal.

Medical conditions such as thyroid disorder, metabolic disorders, certain vitamin deficiencies, tumors, severe depression, normal pressure hydrocephalus (if discovered and treated early enough), reactions to medications, untreated sleep apnea, “brain fog” from chemotherapy, acute illnesses (e.g., urinary tract infections, high fever) may cause temporary inability to function. These possibilities need to be evaluated in anyone showing decline. Any condition that resolves with time or treatment should not be referred to as a dementia. Dementia should be reserved for decline that cannot be resolved.