Dementia Definition – What is Dementia?

Dementia is a term very loosely used to describe muddled or forgetful behavior. But what exactly is dementia? Is it a disease? Does it only affect the elderly? Let's start with a dementia definition using simple, lay-man's language. 

Dementia Definition - In simple terms:  

Dementia is not a disease, although it is often caused by a disease. Dementia is an umbrella term that describes a wide range of symptoms caused by changes in the brain.

Dementia is an umbrella term for a range of symptoms caused when brain cells are damaged. The damage may have been caused by disease, stroke or injury. When dementia occurs, the brains ability to function properly is impaired.

People with dementia may have difficulty remembering or thinking clearly. They may experience personality changes, or they may have difficulty with coordination. Dementia is not a normal part of ageing, although it mostly, but not always, affects the elderly.

Alzheimer’s disease is the most common dementia causing disease, affecting 80% of people diagnosed with dementia.

Dementia Definition - In more detail:

Dementia describes a range of symptoms which affect cognitive, behavioral or physical abilities enough to impede normal daily functioning. The symptoms of dementia are caused by physical changes to the brain whereby brain cells become damaged. The cells degenerate and die more rapidly than they should under normal ageing. Damaged brain cells are unable to communicate properly with other cells. Hence messages sent between brain cells, or to parts of the body, become mixed or ineffective.

The symptoms of dementia will vary from person to person. It all depends on the region of the brain where the damaged brain cells occur. Memory, communication, reasoning or movement may become difficult, leaving a feeling of confusion or frustration.

Dementia is not a specific disease. It is an overall term that describes a wide range of symptoms associated with a decline in memory or other thinking skills severe enough to reduce a person's ability to perform everyday activities. (dementia definition from )

What Causes Dementia?

Brain cell damage resulting in the symptoms which define dementia, may have been primarily or secondarily caused by disease (such as Alzheimer’s disease or Parkinson’s disease), stroke, or injury (such as severe head impact).

  • Most forms of Dementia cannot be inherited, however frontotemporal dementia can sometimes run in families.

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What are the Types of Dementia?

The different conditions or diseases which cause dementia symptoms are commonly referred to as the Types of Dementia. Alzheimer’s disease, Vascular or Parkinson’s disease are some of the most common types of dementia.

What are the Stages of Dementia?

Dementia is progressive, meaning that the symptoms of dementia usually become more severe with time. This decline is commonly referred to as the Stages of Dementia.

What are the Symptoms of Dementia?

  • The symptoms of dementia will vary depending on the region of the brain damaged by the different causes or types of dementia. To be diagnosed as dementia, at least two or more core mental functions must be significantly impaired beyond that considered a normal part of aging. Core mental functions may include:
  • Memory
  • Communication
  • Concentration
  • Reasoning and analysis
  • Perception

Let's look at these symptoms in more detail:

The following covers some of the more common symptoms of dementia. Links are also provided for more detailed medical and scientific dementia definition and descriptions, which are not covered here.

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Dementia causing Memory loss

Forgetfulness is a normal part of ageing, and as memory loss has a number of causes, it is not necessarily a sign of dementia. It is common to have greater difficulty remembering names, places and other things as you age. You may forget the name of an acquaintance you bump into, but you are still aware how and why you know each other. Or you may walk in and out of a room and forget the collect the thing you came for, but you will soon realize what you needed and return to fetch it. Someone with dementia will also forget the context surrounding the person or thing.

* For more detailed medical and scientific dementia definition, refer to: Dementia and the Brain,

Misplacing things

Forgetting where you put your keys and spending 5 minutes looking for them is quite normal at any age. Most people will attempt to keep their keys or other things in the same place each day, establishing an organised routine. However putting things in the wrong place is common for people with dementia. You may find they have placed a bowl in the sock drawer, or put their brush in the fridge. Although most people may keep things in random places occasionally when distracted, someone with dementia might regularly misplace their things.

Language and Communication

“It’s on the tip of my tongue,” is a common phrase to hear. All of us have experienced the annoyance of not being able to find the right word for the right situation. For dementia patients this is a regular problem even for simple words. This leads to feelings of frustration and isolation, as communicating becomes more difficult.

In addition, words can get mixed up and used in the wrong context, or given the wrong meaning. Conversations become more and more basic as it gets increasingly difficult to have sensible conversations with others.

Difficulty following a conversation

Due to the confusion of words and their correct meanings, and difficulty concentrating, conversations make less sense and harder to follow. In addition, the brain slows down with age, even more so with dementia. Hence fast flowing conversations are impossible to keep up with. This leads to further withdrawal and isolation of dementia patients.

Difficulty with everyday tasks

We are all taught in childhood how to perform everyday tasks which we soon take for granted. Tasks like tying shoe laces or brushing our teeth become second nature. Dementia causes confusion whereby everyday tasks become difficult or mixed up. For instance, a person may forget how to use a knife to butter the bread, or forget to put the shirt on before the coat, or the socks before the shoes.

Difficulty learning new tasks

It is hard to teach an old dog new tricks, or so the saying goes. With dementia patients, concentrating and learning become even more difficult. Following instructions, be they verbal or written, is especially problematic. Although it is unlikely someone with dementia will enroll in a class or attempt to learn a new language, they may find themselves needing to operate a new television control unit, or to change the battery on their hearing aids.

Many of today’s modern gadgets, such as telephones or tablets, are designed to be intuitive. But their simplicity makes them increasingly complex for the elderly, and for dementia patients in particular. Even a microwave or electric kettle will pose problems.

Difficulty keeping track of regular events

We perform many daily events like clockwork, without a second thought. Eating breakfast first thing in the morning, or watching the 6pm news, may be some of our regular routines. People with dementia may have difficulty remembering daily routines they have been performing for decades. Weekly routines, like putting out the trash, are even more likely to be skipped.

Poor or decreased judgement

People with dementia may end up wearing miss-matched clothing without realising it. Or they may put on a heavy coat in the Summer time. What they perceive may be quite different to the reality and they may be easily annoyed if their bad judgement is pointed out.

Another example of decreased judgment comes from their inability to reason and analyse situations fully. For instance they may be easily convinced to spend money on unnecessary items. Or they may put out a just few cookies, when a large family group has come to visit.


Disorientation is the symptom of dementia most well-known amongst the general population. This is due in no small part to films and television, which like to portray confused elders wondering around the streets unable to locate their home. People with dementia may be easily lost in familiar surroundings, unable to remember how to get to where they need to be. Often they cannot remember why they are there at all. These situations are extremely frustrating and stressful, making it difficult to assist if you come across someone who is lost in this manner.

It is also common for dementia patients to assume they are in another city or building. Perhaps they are confused with a city they used to live in at one time, or with an old work place, or previous home.

Disorientation in time

Eating dinner first thing in the morning, or dressing for an outing in the middle of the night are examples of disorientation in time. Regular daily routines are forgotten with dementia. Things to do may be remembered at odd moments in the day, and enacted without regard for the time of day.

Changes in mood or behavior

Some people are often described as being happy or optimistic, whist others are more prone to feelings of melancholy or grumpiness. Whatever a person’s general mood, it is acceptable for changes in mood to occur depending on any number of factors.  Changes in behavior such as lashing out in anger may also be justified as a reaction to a certain situation. A person with dementia, on the other hand, may demonstrate unusual behavior, emotions or mood swings for no apparent reason. They may also show no emotion or less emotion than you might expect at certain times.

Personality changes

Frustration, as has been mentioned in many of the symptoms above, is a common manifestation of dementia. Difficulty with remembering, following conversations, completing tasks or recognizing places leads to frustration, and in turn feelings of anxiousness or agitation. This is understandable, however dementia can induce other changes in personality which are not so easily explained. Many dementia patients become suspicious of others, depressed, or unnecessarily distracted by nothing in particular. It is not uncommon for family members to describe this as “not her usual self,” without being able to clearly express in what way.

Loss of interest

Dementia patients may lose interest in life’s daily challenges, preferring to pass time in bed or in front of the television. They stop seeking activities with which to keep busy. Should others make suggestions of things to do, they may seem apathetic or passive. It would appear they have lost all initiative and interest in activities or hobbies.

* For more detailed medical and scientific dementia definition, refer to: What is Dementia?

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