What is dementia? The signs, symptoms and causes of dementia

Dementia is a term used to describe various symptoms of cognitive decline such as forgetfulness, but is not a clinical diagnosis itself until an underlying disease or disorder has been identified.

Dementia is a collective term used to describe the problems that people with various underlying brain disorders or damage can have with their memory, language and thinking.Alzheimer's disease is the best known and most common disorder under the umbrella of dementia.

Contents of this article:

 
1. 1. What is dementia?
 
2. 2. What causes dementia?
 
3. 3. Signs and symptoms
 
4. 4. Tests and diagnosis
 
5. 5. Treatment and prevention

What is dementia?

Dementia is not a single disease in itself, but a general term to describe symptoms such as impairments to memory, communication and thinking.¹

While the likelihood of having dementia increases with age, it is not a normal part of aging. Before we had today's understanding of specific disorders, "going senile" used to be a common phrase for dementia ("senility"), which misunderstood it as a standard part of getting old. ^1,2

Light cognitive impairments, by contrast, such as poorer short-term memory, can happen as a normal part of aging (we slowly start to lose brain cells as we age beyond our 20s³). This is known as age-related cognitive decline, not dementia, because it does not cause the person or the people around them any problems.¹Dementia describes two or more types of symptom that are severe enough to affect daily activities.

Symptoms that are classed as "mild cognitive impairment" - which, unlike cognitive decline, are not a normal part of aging - do not qualify as dementia either, since these symptoms are not severe enough.¹ For some people though, this milder disease leads to dementia later on.⁴

A number of brain disorders with more severe symptoms are classified as dementias, with Alzheimer's disease being the best known and most common.

An analysis of the most recent census estimates that 4.7 million people aged 65 years or older in the US were living with Alzheimer's disease in 2010.⁵ The Alzheimer's Association has used this analysis to number-crunch the extent of the disorder in its 2013 report. It 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.

The non-profit organization says Alzheimer's accounts for between 60% and 80% of all cases of dementia, with vascular dementia caused by stroke being the second most common type.

What causes dementia?

All dementias are caused by brain cell death,¹ and neurodegenerative disease - progressive brain cell death that happens over a course of time - is behind most dementias.^4,6

Nerve cells (neurons) in the brain - loss or damage can cause dementia. Alzheimer's disease is the leading cause.

But as well as progressive brain cell death like that seen in Alzheimer's disease, dementia can be caused by a head injury, a stroke or a brain tumor, among other causes.⁶

Some of the causes are simpler to understand in terms of how they affect the brain and lead to dementia:¹

• Vascular dementia - this results 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 received by sports players - have been linked to certain dementias appearing later in life. Evidence is weak, however, that a single brain injury will raise the likelihood of having a degenerative dementia such as Alzheimer's disease.⁷

Dementia can also be caused by:^1,2,8

• Prion diseases - from certain types of protein, as in CJD (Creutzfeldt-Jakob disease) and GSS (Gerstmann-Straussler-Scheinker syndrome).
• HIV infection - when the problem is simply termed HIV-associated dementia. 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 (for example, thiamine/B1, leading to Wernicke-Korsakoff syndrome, which is most often caused by alcohol misuse), and thyroid abnormalities.

Alzheimer's dementia is caused by progressive brain cell death. Estimates range between 60% and 80% for the proportion of all cases of dementia being accounted for by Alzheimer's disease.² In the US, about 5.3 million people are thought to have the disorder among the estimated 6.8 million individuals who have some form of dementia.⁴

Alzheimer's is thought to be caused by "plaques" between the dying cells in the brain and "tangles" within the cells (both are protein abnormalities: a build-up of "beta-amyloid" in plaques and the disintegration of "tau" protein in tangles).

These inclusions in the brain are always present with the disorder but whether they are themselves the cause, or if there is some other underlying process, is not known - and there is some overlap with other disorders that show similar changes in brain cells.^1,9

The brain tissue in a person with Alzheimer's has progressively fewer nerve cells and connections, and the total brain size shrinks.^1,9

Dementia with Lewy bodies is also caused by neurodegeneration linked to abnormal structures in the brain. Here, the brain changes involve a protein called alpha-synuclein.¹⁰

Mixed dementia refers to a diagnosis of two or three types occurring together. A person may show both Alzheimer's disease and vascular dementia at the same time. Or the combination could be Lewy bodies and Alzheimer's. There can also be a combination of all three types.¹⁰

Parkinson's disease is also marked by the presence of Lewy bodies. While the part of the brain affected means there are classic movement symptoms, people with Parkinson's can also go on to develop dementia symptoms as the degenerative changes in the brain gradually spread.¹⁰

Huntington's disease is similar to Parkinson's in the respect of being classically marked by uncontrolled movements yet having dementia as a component. It results in mood changes, too. Huntington's is an inherited condition caused by a single faulty gene. This can produce the disease at any age - as young at 2 years of age and as old as 80, but typically between the ages of 30 and 50 years.¹⁰

Other disorders leading to symptoms of dementia include:¹⁰

• Frontotemporal dementia (also known as Pick's disease)
• Normal pressure hydrocephalus (when excess cerebrospinal fluid accumulates in the brain)
• Posterior cortical atrophy (caused by the same tissue abnormalities seen in Alzheimer's disease, but in a different part of the brain), and
• Down syndrome (people born with this are more likely to develop young-onset Alzheimer's).

Recent developments on causes of dementia 

Link found between dementia and vitamin D deficiency - In what is regarded as the first large, population-based study of its kind, a team of researchers has found a link between vitamin D consumption and the risk of developing dementia. Older people who do not get enough vitamin D could double their risk of developing the condition.

Signs and symptoms

Memory loss in dementia can be serious enough for the person to forget where they are, even on their home street.

The symptoms of dementia experienced by patients, or noticed by people close to them, are exactly the same signs that healthcare professionals look for. Therefore, detailed information on these is given in the next section about tests and diagnosis.

A person with dementia may show any of the following problems, mostly due to memory loss - some of which they may notice (or become frustrated with) themselves, while others may only be picked up by carers or healthcare workers as a cause for concern. The signs used to compile this list are published by the American Academy of Family Physicians (AAFP) in the journal American Family Physician:⁶

• Recent memory loss - a sign of this might be asking the same question repeatedly, forgetting about already asking it.
• Difficulty completing familiar tasks - for example, making a drink or cooking a meal, but forgetting and leaving it.
• Problems communicating - difficulty with language by forgetting simple words or using the wrong ones.
• Disorientation - with time and place, getting lost on a previously familiar street close to home, for example, and forgetting how they got there or would get home again.
• Poor judgment - the AAFP says: "Even a well person might get distracted and forget to watch a child for a little while. People with dementia, however, might forget all about the child and just leave the house for the day."
• Problems with abstract thinking - for example, dealing with money.
• Misplacing things - including putting them in the wrong places and forgetting about doing this.
• Mood changes - unlike those we all have, swinging quickly through a set of moods.
• Personality changes - becoming irritable, suspicious or fearful, for example.
• Loss of initiative - showing less interest in starting something or going somewhere.

The Alzheimer's Association has put together Know the 10 signs - a PDF document listing real-life examples of how this type of dementia can affect people.

Tests and diagnosis

The first step in testing concerns about memory performance and cognitive health involves standard questions and tasks. Asking for knowledge of facts that should be known to any adult will give healthcare professionals an indication of whether there is dementia or not and help to guide a decision on further investigation. Simple word knowledge tests and drawing tasks are included alongside memory questions.

It is important that healthcare professionals carry out standardized testing of cognition, as opposed to gaining informal impressions of a person's mental abilities. Research has shown that dementia cannot be reliably differentiated without using the standard tests below, completing them fully and recording all the answers before forming a diagnostic indication that also takes account of other factors.¹¹

Equally important is that people with concerns about their own or someone else's possible dementia get the problem checked by a doctor, both because of the confusing nature of the symptoms and because there are various causes that could need checking and treating.

Cognitive tests

Today's cognitive tests are in widespread use and have been verified as a reliable way of indicating dementia.¹¹ They have changed little since being established in the early 1970s. The simple questions that are used come from a set first developed in 1972 by Professor Henry Hodkinson, working at the time in a London hospital as a UK specialist in geriatric medicine.¹²

Prof Hodkinson's research identified the most effective 10 questions in a previous list of 26 to screen older people in confused states. The questionnaire - which is one of the dementia tools most commonly used by family and hospital doctors¹¹ - is known as the abbreviated mental test score (AMTS).

The abbreviated mental test score has 10 questions:¹²

1.  What is your age?
2. What is the time, to the nearest hour?
3.  Repeat an address at the end of the test that I will give you now (e.g. "42 West Street")
4.  What is the year?
5.  What is the name of the hospital or town we are in?
6.  Can you recognize two people (e.g. the doctor, nurse, home help, etc.)?
7.  What is your date of birth?
8.  In what year did World War 1 begin? (Other widely known dates in the past can be used.)
9.  Name the president/prime minister/monarch.
10.  Count backwards from 20 down to 1.

Each correct answer attracts one point; scoring seven or more indicates normal functioning while getting six points or fewer suggests cognitive impairment.¹¹

People with dementia might forget where in this circle to write the hours of a clock face. One test for this also asks the patient to draw in hands at ten past eleven.

The GPCOG test is briefer than the AMTS in terms of the questions asked of the patient, but if these raise concern there is an added element for recording the observations of relatives and carers.

Designed for GPs, this sort of test may be the first formal assessment of a person's mental ability that is done before fuller tests are considered.¹³

The doctor records the answers to questions and tasks given at the GPCOG test website.

This online diagnostic tool returns a score after the first, patient-based set of questions, then prompts whether "more information is required" from relatives in a second step. At the end of the two-part test, a statement is given on whether "cognitive impairment is indicated". The test was developed at Australia's University of New South Wales.

One task for the patient part of the GPCOG test is to write the hours of a clock face around a blank circle on a piece of paper - with accurate relative spacing - and then draw the hour and minute hands to show ten past eleven.

The second part of the test, which probes someone "close to the person" being evaluated - the informant interview - has six questions around the following areas of cognition, finding 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. "Further and special investigations" may also be needed.

Cognitive checklists measure dementia symptoms and other tests also help to narrow down, for example, Alzheimer's disease.

The clinical tests (see below) will identify, or rule out, treatable causes for the memory loss and help to narrow down whether there is a degenerative cause such as Alzheimer's disease.

The mini mental state examination (MMSE) is a fuller cognitive test. The shorter tests above are reliable alternatives to the MMSE, and considered more effective in some settings.^13,14

Primary care doctors have less time but are in a good position to do the initial screening with shorter tests, while specialists will be referred to for further evaluation with, for example, the MMSE alongside other testing to confirm whether there is dementia and diagnose the particular type.⁴

In some settings, it is standard for all patients to skip straight to the MMSE as the first screen for dementia. For example, all older people in a geriatric healthcare setting may be tested on admission.

The mini mental state examination measures:^4,15

• Orientation to time and place
• Word recall
• Language abilities
• Attention and calculation
• Visuospatial skills.

Abilities to name objects, follow verbal and written commands, write a sentence spontaneously and copy a complex shape are tested.¹

The maximum possible score is 30 points and dementia is suggested at scores of up to between 24 and 27, with normal being anything over this.

Doctors should consider adjustments for age and education because performance in the test can be influenced by demographic, non-dementia factors.^14,16 The following should be taken into account:¹⁴

• Educational level, skills, prior level of functioning and attainment
• Language and culture
• Any sensory impairments (for example, hearing loss)
• Psychiatric illness or physical/neurological problems.

The mini mental state examination is used to help diagnose dementia caused by Alzheimer's disease and also to rate its severity and when drug treatment is needed. Mild-to-moderate Alzheimer's disease is classified by an MMSE score below 26, moderate disease is below 20 but above 10, and severe Alzheimer's produces a score of less than 10.^14,16

Other tests

The cognitive tests above are central to diagnosing whether dementia is present and for tracking progression and severity after a particular disorder is confirmed.

At the earliest stages of diagnosis, before a disorder such as Alzheimer's can be narrowed down, other tests are done, often to rule out treatable causes or pinpoint a dementia with an obvious cause. The other reason for more tests is that different diseases can overlap.

Doctors will "take a history" (ask the patient questions), carry out a physical examination to uncover any signs of, for example, a stroke, heart condition or kidney disease and check neurological function, by testing balance, senses and reflexes.¹

Depending on what the doctor thinks could need further investigation, other diagnostics include laboratory tests of blood and urine samples, brain scans (possibly including CT, MRI, and EEG), genetic testing in the case of suspected inherited disorders such as Huntington's, and sometimes psychiatric assessment if, for example, depression may be involved.¹

Recent developments in tests and diagnosis 

Four biomarkers of dementia have been suggested by other work, published in Neurology in August 2012. Research into blood plasma levels of different "analytes" identified four that were altered in people with Alzheimer's and milder forms of dementia (apoE, B-type natriuretic peptide, C-reactive protein and pancreatic polypeptide).

Physical abilities of the "oldest old". In people aged 90 years or more, performance in measures such as grip strength, standing balance, a 4-meter walk and "chair stands" was linked to dementia risk in a University of California, Irvine, study reported in the Archives of Neurology in January 2013. The researchers ask whether this and further research could uncover a cause-and-effect relationship to physical abilities and help with the early identification of risk factors and with the prevention of dementia.

Treatment and prevention

Brain cell death cannot be reversed so there is no known treatment to cure a degenerative cause of dementia symptoms or fully halt its progress. Management of disorders such as Alzheimer's disease is instead focused on providing care and treating symptoms rather than their underlying cause.^1,3

If dementia symptoms are due to a reversible, non-degenerative cause, however, treatment may be possible, to prevent or halt further brain tissue damage.^1,3 Examples include injury, medication effects, vitamin deficiency.

Symptoms of Alzheimer's disease can be reduced by drugs to help improve an individual's quality of life - there are four drugs in a class called cholinesterase inhibitor approved for this in the US:¹

• 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.¹

A cholinesterase inhibitor such as donepezil can also help with the behavioral elements of Parkinson's disease.¹

Other quality-of-life care

A therapeutic robot companion shown with its researcher, Professor Cook.

"Brain training" can help in the early stages of Alzheimer's to improve cognitive functioning and help deal with forgetfulness. This might involve the use of mnemonics and other memory aids such as computerized recall devices.¹

Of course, care from healthcare professionals, and relatives to some extent, can help people with the later stages of dementia.

There have been some tech developments in this area, too - an innovation to provide a therapeutic robot companion has been shown to help sufferers be less anxious, aggressive and lonely. See our news story - Robo-pets help dementia patients - about the PARO baby seal reported in the May 2013 issue of the Journal of Gerontological Nursing. The picture shows the baby seal with Northumbria University's Professor Glenda Cook, one of the report's authors.

Prevention

Certain risk factors are known to be associated with dementia and many of them are modifiable - something we can act on and so possibly contribute to avoiding dementia. But age is the biggest predictor of dementia, and there is nothing we can do to reverse this, of course.

Other risk factors include:¹

• 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)
• Diabetes, which is also a risk factor for cardiovascular disease and stroke, which may lead to vascular dementia
• Mild cognitive impairment, which can sometimes, but not always, lead to dementia.

There is a lot of research into risk factors associated with Alzheimer's disease so there may be lifestyle measures we can take to potentially reduce our risk and enjoy a healthier life more generally. Medical News Today has a page compiling ideas from researchers on how to prevent Alzheimer's disease and dementia - including information about heart health, diet, exercise and keeping an active brain.

References:

1.        National Institute of Neurological Disorders and Stroke. Dementia: hope through research. Bethesda, MD: Office of Communications and Public Liaison, National Institute of Neurological Disorders and Stroke, US National Institutes of Health. Published online; version last updated 26th June 2013 accessed 21st October 2013. Summary information.

2.        Alzheimer’s Association. What is dementia? Published online, accessed 21st October 2013. Also, PDF report published online: 2013 Alzheimer’s disease facts and figures accessed 21st October 2013.

3.        American Academy of Family Physicians. Dementia: overview. FamilyDoctor.org, accessed 21st October 2013.

4.        DeFina PA, Moser RS, Glenn M, Lichtenstein JD and Fellus J. Alzheimer's disease clinical and research update for health care practitioners. Journal of Aging Research, volume 2013 (e-publication, 4th September 2013), article ID: 207178.

5.        Hebert LE, Weuve J, Scherr PA and Evans DA. Alzheimer disease in the United States (2010-2050) estimated using the 2010 census. Neurology, 2013. Published online before print 6th February 2013 (DOI: 10.1212/WNL.0b013e31828726f5).

6.        American Academy of Family Physicians. The signs of dementia (patient information). American Family Physician, 2001, volume 63 (number 4), pages 717-718.

7.        Alzheimer’s Association. What is dementia? Traumatic brain injury. Published online, accessed 21st October 2013.

8.        FCA. Dementia - is this dementia and what does it mean? San Francisco, CA: Family Caregiver Alliance. Fact sheet published online, accessed 21st October 2013.

9.        Alzheimer’s Association. The role of plaques and tangles. Published online, accessed 21st October 2013.

10.     Alzheimer’s Association. Types of dementia. Published online, accessed 21st October 2013.

11.     Burleigh E, Reeves I, McAlpine C and Davie J. Can doctors predict patients' abbreviated mental test scores (PDF) Age and Ageing, 2002, volume 31, issue 4, pages 303-306. Abstract.

12.     Hodkinson HM. Evaluation of a mental test score for assessment of mental impairment in the elderly. Age and Ageing, 2012, volume 41, supplement 3, pages iii35-40. Reprint of original 1972 paper published online (DOI: 10.1093/ageing/afs148).

13.     Alzheimer’s Association. Cognitive assessment information on Alzheimer’s disease for healthcare professionals. Published online, accessed 21st October 2013.

14.     NICE. Diagnosis and assessment of dementia. In: Dementia: Supporting people with dementia and their carers in health and social care, NICE clinical guideline. London, UK: National Institute for Health and Care Excellence, November 2006.

15.     Folstein MF, Folstein SE, McHugh PR. "Mini-mental state". A practical method for grading the cognitive state of patients for the clinician. Journal of Psychiatric Research, 1975, volume 12, number 3: pages 189-198.

16.     Alzheimer’s Society. The mini mental state examination (MMSE). Fact sheet published online, accessed 21st October 2013.

17.     Moreno JA, Halliday M, Molloy C and others. An oral treatment targeting the unfolded protein response prevents prion neurodegeneration and clinical disease in mice. Science Translational Medicine, 2013, volume 5, issue 206, page 206ra138 (DOI: 10.1126/scitranslmed.3006767).

18.     Cooper C. Alzheimer’s treatment breakthrough: British scientists pave way for simple pill to cure disease. The Independent, 10th October 2013. Published online, accessed 21st October 2013.