Dementia is a collective term used to describe various symptoms of cognitive decline, such as forgetfulness. It is a symptom of several underlying diseases and brain disorders.
This article discusses the potential causes of dementia, the various types, and any available treatments.
Contents of this article:
Fast facts on dementia
Here are some key points about dementia. More detail and supporting information is in the main article.
- There are an estimated 47.5 million dementia sufferers worldwide
- One new case of dementia is diagnosed every 4 seconds
- Dementia mostly affects older people, but is not a normal part of aging
What is dementia?
Dementia is not a normal part of aging.
Dementia is not a single disease in itself, but a general term to describe symptoms such as impairments to memory, communication, and thinking.
While the likelihood of having dementia increases with age, it is not a normal part of aging.
Light cognitive impairments, such as poorer short-term memory, can happen as a normal part of aging. This is known as age-related cognitive decline rather than dementia because it does not cause significant problems.
Dementia describes two or more types of symptom that are severe enough to affect daily activities.
An analysis of the most recent census estimates that 4.7 million people aged 65 years or older in the United States were living with Alzheimer's disease in 2010. The Alzheimer's Association estimates that:
- Just over a tenth of people aged 65 years or more have Alzheimer's disease
- This proportion rises to about a third of people aged 85 and older
- Alzheimer's accounts for 60-80 percent of all cases of dementia
Causes of dementia
Dementias can be caused by brain cell death, and neurodegenerative disease - progressive brain cell death that happens over time - is behind most dementias.
- Vascular dementia - resulting from brain cell death caused by conditions such as cerebrovascular disease, for example, stroke. This prevents normal blood flow, depriving brain cells of oxygen.
- Injury - post-traumatic dementia is directly related to brain cell death caused by injury.
Some types of traumatic brain injury - particularly if repetitive, such as those received by sports players - have been linked to certain dementias appearing later in life. Evidence is weak, however, that a single brain injury raises the likelihood of having a degenerative dementia such as Alzheimer's disease.
- Prion diseases - for instance, CJD (Creutzfeldt-Jakob disease)
- HIV infection - how the virus damages brain cells is not certain
- Reversible factors - some dementias can be treated by reversing the effects of underlying causes, including medication interactions, depression, vitamin deficiencies, and thyroid abnormalities
Types of dementia
Alzheimer's is characterized by "plaques" between the dying cells in the brain and "tangles" within the cells (both are due to protein abnormalities).
The brain tissue in a person with Alzheimer's has progressively fewer nerve cells and connections, and the total brain size shrinks.
Dementia with Lewy bodies is a neurodegenerative condition linked to abnormal structures in the brain. The brain changes involve a protein called alpha-synuclein.
Mixed dementia refers to a diagnosis of two or three types occurring together. For instance, a person may show both Alzheimer's disease and vascular dementia at the same time.
Parkinson's disease is also marked by the presence of Lewy bodies. Although Parkinson's is often considered a disorder of movement, people with Parkinson's can also go on to develop dementia symptoms.
Huntington's disease is characterized by specific types of uncontrolled movements but also includes dementia.
Other disorders leading to symptoms of dementia include:
- Frontotemporal dementia (also known as Pick's disease)
- Normal pressure hydrocephalus (when excess cerebrospinal fluid accumulates in the brain)
- Posterior cortical atrophy (resembles changes seen in Alzheimer's disease, but in a different part of the brain)
- Down syndrome (increases the likelihood of young-onset Alzheimer's)
Symptoms of dementia
Dementia symptoms include memory loss, disorientation, and mood changes.
A person with dementia may show any of the problems listed below, mostly due to memory loss - some of which they may notice themselves, while others may only be picked up by caregivers or healthcare workers.
The signs used to compile this list are published by the American Academy of Family Physicians (AAFP) in the journal American Family Physician:
Possible symptoms of dementia:
- Recent memory loss - a sign of this might be asking the same question repeatedly
- Difficulty completing familiar tasks - for example, making a drink or cooking a meal
- Problems communicating - difficulty with language; forgetting simple words or using the wrong ones
- Disorientation - getting lost on a previously familiar street, for example
- Problems with abstract thinking - for instance, dealing with money
- Misplacing things
- Mood changes
- Personality changes - perhaps becoming irritable, suspicious or fearful
- Loss of initiative - showing less interest in starting something or going somewhere
The first step in testing memory performance and cognitive health involves standard questions and tasks.
Asking simple questions, such as "who is President?" will give doctors an indication of whether there is dementia or not and help to decide whether further investigation is needed.
Simple word knowledge tests and drawing tasks are included alongside memory questions.
Research has shown that dementia cannot be reliably diagnosed without using the standard tests below, completing them fully, and recording all the answers; however, diagnosis also takes account of other factors.
Cognitive dementia tests
Today's cognitive dementia tests are widely used and have been verified as a reliable way of indicating dementia. They have changed little since being established in the early 1970s.
The abbreviated mental test score has 10 questions which include:
- What is your age?
- What is the time, to the nearest hour?
- What is the year?
- What is your date of birth?
Each correct answer gets one point; scoring six points or fewer suggests cognitive impairment.
The General Practitioner Assessment of Cognition (GPCOG) test includes an added element for recording the observations of relatives and caregivers.
Designed for doctors, this sort of test may be the first formal assessment of a person's mental ability.
The second part of the test probes someone close to the patient and includes six questions to find out whether the patient has:
- Become less able to remember recent events or conversations
- Begun struggling to find the right words or using inappropriate ones
- Found difficulty managing money or medications
- Needed more help with transport (without the reason being, for example, injury)
If the test does suggest memory loss, standard investigations are then recommended, including routine blood tests and a CT brain scan.
Clinical tests will identify, or rule out, treatable causes of memory loss and help to narrow down potential causes, such as Alzheimer's disease.
The mini-mental state examination (MMSE) is a cognitive test which measures:
- Orientation to time and place
- Word recall
- Language abilities
- Attention and calculation
- Visuospatial skills
The MMSE is used to help diagnose dementia caused by Alzheimer's disease and also to rate its severity and whether drug treatment is needed.
Treatments for dementia
Brain cell death cannot be reversed, so there is no known cure for degenerative dementia. Management of disorders such as Alzheimer's disease is instead focused on providing care and treating symptoms rather than their underlying cause.
If dementia symptoms are due to a reversible, non-degenerative cause, however, treatment may be possible to prevent or halt further brain tissue damage. Examples include injury, medication effects, and vitamin deficiency.
Symptoms of Alzheimer's disease can be reduced by some medications. There are four drugs, called cholinesterase inhibitors, approved for use in the U.S.:
- Donepezil (brand name Aricept)
- Alantamine (Reminyl)
- Rivastigmine (Exelon)
- Tacrine (Cognex)
A different kind of drug, memantine (Namenda), an NMDA receptor antagonist, may also be used, alone or in combination with a cholinesterase inhibitor.
Cholinesterase inhibitors can also help with the behavioral elements of Parkinson's disease.
Other quality-of-life care
"Brain training" can help improve cognitive functioning and help deal with forgetfulness in the early stages of Alzheimer's. This might involve the use of mnemonics and other memory aids such as computerized recall devices.
Prevention of dementia
Certain risk factors are known to be associated with dementia. However, age is the biggest predictor. Other risk factors include:
- Smoking and alcohol use
- Atherosclerosis (cardiovascular disease causing the arteries to narrow)
- High levels of "bad" cholesterol (low-density lipoprotein)
- Above-average blood levels of homocysteine (a type of amino acid)
- Mild cognitive impairment can sometimes, but not always, lead to dementia