You’ve just been told that someone you know has dementia. You know that’s not a good thing, but you also aren’t really sure exactly what it means. Is it possible to grasp the idea without getting into too much medical detail?

A Decline in Mental Ability

Dementia is a general term for a condition highlighted by a decline in mental ability that’s severe enough to interfere with daily life. Alzheimer’s disease is the most common type of dementia. When memory loss becomes pronounced enough to impact daily living, it also becomes a type of dementia.

It’s Not a Disease

We just said that Alzheimer’s disease is a type of dementia, but it’s important to understand that dementia is not a disease. It’s a general term that describes a wide variety of symptoms that are associated with a decline in memory. When this decline becomes severe enough to reduce someone’s ability to perform everyday activities, it’s called dementia.

About 60% to 80% of dementia—or the inability to perform daily activities—is caused by Alzheimer’s disease. Brain circulation changes, including strokes are the second most common cause of dementia. This is specifically known as vascular dementia. These two biggest causes of dementia are irreversible.

Memory loss is not dementia. Memory loss often is simply a part of the aging process, and mild general forgetfulness is not a symptom of Alzheimer’s disease or any other type of dementia. Some causes of dementia are correctable. An example of a reversible dementia might be a vitamin deficiency, depression or medication side effects or a thyroid problem. In fact, some memory problems can be resolved with medical help. If you know someone who struggling with sudden onset memory problems or other cognitive changes, they should see a physician as soon as possible.


Symptoms vary greatly; however, at least two of these core mental functions have to be significantly impaired for someone to be diagnosed with dementia:

  • Memory
  • Communication or language
  • Ability to focus and pay attention
  • Reasoning and judgement
  • Visual perception

People often first display signs of dementia by experiencing short-term memory problems, such as keeping track of personal items or remembering appointments. It may progress to interfering with their ability to do things like prepare meals or pay bills. The symptoms will start out slowly and gradually get worse.


Dementia is caused by damage to brain cells. It interferes with the ability of these cells to communicate with each other. In the case of Alzheimer’s disease, elevated levels of certain proteins inside and outside brain cells make it difficult for brain cells to stay healthy and to communicate with each other. The hippocampus is the center for memory in the brain. Cells in this region are the first to be damaged. This is why memory loss is often one of the earliest symptoms of Alzheimer’s disease.

There’s no single medical test to determine and diagnose dementia or its cause. This is mainly because the physical manifestations of dementia often overlap. It takes a careful study of someone’s medical history, lab tests, and a thorough physical examination to start the process.

There’s still much to be learned about the causes of dementia. Dementia is a group of symptoms. And, the diseases that cause dementia are what need to be treated.