Dementia

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Contents

Introduction

General Description

The term ‘dementia’ is derived from the Latin word 'demens' meaning ‘without mind’. Dementia is the progressive decline in cognitive function due to damage or disease in the brain beyond what might be expected from normal ageing. Particularly affected areas may be memory, attention, language, and problem solving. Especially in the later stages of the condition, affected persons may be disoriented in time (not knowing what day of the week, day of the month, month, or even what year it is), in place (not knowing where they are), and in person (not knowing who they are).

Dementia is most common in elderly people; it used to be called senility and was considered a normal part of aging. We now know that dementia is not a normal part of aging but is caused by a number of underlying medical conditions that can occur in both elderly and young individuals. In some cases, dementia can be reversed with proper medical treatment. In others, it is permanent and gets worse over time.

Comparison of a normal aged brain (left) and an Alzheimer's patient's brain (right)


Types and Classifications of Dementia

There are over 100 illnesses and conditions that can result in dementia — a comprehensive list of these is included in the International Statistical Classification of Diseases and Related Health Problems (ICD), 10th Revision (WHO 1992a) [1]. The ICD approaches dementia from a disease perspective, attempting to identify the underlying aetiology; and the DSM[2] and International Classification of Functioning, Disability and Health (ICF)[3] which both approach dementia from a perspective of functional outcomes. There are many different types and causes of dementia. According to the National Institutes of Health[4], Alzheimer's disease is the most common cause of dementia, followed by vascular dementia. Vascular dementia is caused by a lack of blood to the brain, often following a stroke. Other types of dementia include:

The Brain Regions

Dementia is classified in many different ways. Some physicians and scientists classify dementia as being either cortical or subcortical. Cortical dementia occurs as a result of impairment or damage to the cerebral cortex. This is the outer layer of the brain and is associated with memory and language, along with many other aspects of consciousness. Cortical dementias (e.g., Alzheimer's disease, Creutzfeldt-Jakob disease) often result in loss of memory and language skills.

Subcortical dementia results from impairment or damage to parts of the brain underneath the cerebral cortex. Because the cortex can be undamaged, people with subcortical dementia (such as those with Huntington’s disease) rarely experience memory loss and problems with language. Instead, people with subcortical dementia can experience behavior and personality changes, resulting in socially inappropriate and unusual actions.

Risk Factors for Dementia

The biggest risk factor for dementia is age. People over the age of 85 are more likely to experience the condition, although some forms of dementia occur in people under the age of 50. Some individuals are genetically more susceptible to develop certain forms of dementia [5], such as Alzheimer's and Huntington’s diseases. Additionally, several factors can cause temporary or permanent dementia, such as:

  • Brain injuries (including damage caused by stroke)
  • Malnutrition
  • Infections
  • Reaction to medication
  • Poisoning
  • Brain tumor or lesion

Demographic Statistics

  • About 4-5 million people in the United States have some degree of dementia, and that number is expected to increase over the next few decades with the ageing of the population.
  • Dementia affects about 1% of people aged 60-64 years and as many as 30-50% of people older than 85 years. It is the leading reason for placing elderly people in institutions such as nursing homes [4].
  • In Japan roughly 3.1 million people have some degree of dementia, with over 66% of them remaining at home in the care of their families.

Economic Factors

Worldwide, Direct costs associated with dementia were $315.4 billion in 2005, including $105 billion for informal (non-professional) care provided by family members (37 percent). Seventy-seven percent of the total costs occur in the more developed regions that have 46 percent of the prevalence. Worldwide prevalence may quadruple to nearly 120 million by 2050.[2]

Interventions and Challenges

Current research focuses on many different aspects of dementia. Research promises to improve the lives of people affected by the dementia and may eventually lead to ways of preventing or curing associated disorders.

Research on the causes of dementia

These include studies of genetic factors, neurotransmitters, inflammation, factors that influence programmed cell death in the brain. Researchers are trying to determine the possible roles of cholesterol, cholesterol metabolism, oxidative stress (chemical reactions that can damage proteins, DNA,and lipids inside cells), and microglia in the development of dementia. Scientists also are investigating the role of aging-related proteins such as the enzyme telomerase[6].

Since dementia has been linked to abnormal clumps of proteins in cells, researchers are trying to learn how these clumps develop, how they affect cells, and how the clumping can be prevented. Some studies are examining whether changes in white matter - nerve fibres lined with myelin - may play a role in the onset of dementia.

Researchers are searching for additional genes that may contribute to dementia. Some studies suggest that people could eventually be screened for a number of genes that contribute to dementia and receive treatments that specifically address their individual genetic risks. However, such individualized screening and treatment is still years away.

Early Studies on Cause

  • Several studies have found a reduced risk of dementia in people who take cholesterol-lowering drugs called statins. However, it is not yet clear if the apparent effect is due to the drugs or to other factors.
  • Early studies of estrogen suggested that it might help prevent dementia in older women. However, a clinical study of several thousand postmenopausal women aged 65 or older found that combination therapy with estrogen and progestin substantially increased the risk of dementia. Oestrogen alone, also appeared to slightly increase the risk of dementia in this study.

Diagnosis of Dementia

Improving early diagnosis of dementia is important not only for patients and families, but also for researchers who seek to better understand the causes of the disease and find ways to reverse or halt it at early stages. Improved diagnosis can also reduce the risk that people will receive inappropriate treatments. Ongoing studies [7] are investigating whether three-dimensional computer models of PET and MRI images can identify brain changes typical of early dementia, before any symptoms appear.

Vaccines and Treatments for Dementia

Researchers are continually working to develop new drugs for dementia. Many researchers believe a vaccine that reduces the number of amyloid plaques in the brain might ultimately prove to be the most effective treatment for dementia. In 2001, researchers began one clinical trial of a vaccine called AN-1792 [8]. The study was halted after a number of people developed inflammation of the brain and spinal cord. Despite these problems, one patient appeared to have reduced numbers of amyloid plaques in the brain. Other patients showed little or no cognitive decline during the course of the study, suggesting that the vaccine may slow or halt the disease. Researchers are now trying to find safer and more effective vaccines for dementia.

A clinical trial called the Vitamins to Slow Alzheimer's Disease (VITAL) [9] study is testing whether high doses of three common B vitamins - folic acid, B12, and B6 - can reduce homocysteine levels and slow the rate of cognitive decline in Alzheimer's Disease.

Since many studies have found evidence of brain inflammation in Alzheimer's Disease, some researchers have proposed that drugs that control inflammation, such as Non Steriodal Anti Inflammatorys (NSAIDs), might prevent the disease or slow its progression. Studies in mice have suggested that these drugs can limit production of amyloid plaques in the brain. Early studies of these drugs in humans have shown promising results. However, a large National Institue of Health (USA) funded clinical trial of two NSAIDS (naproxen and celecoxib) to prevent Alzheimer's Disease was stopped in late 2004 because of an increase in stroke and heart attack in people taking naproxen, and an unrelated study that linked celecoxib to an increased risk of heart attack.

Some studies have suggested that two drugs, pentoxifylline and propentofylline, may be useful in treating vascular dementia. Pentoxifylline improves blood flow, while propentofylline appears to interfere with some of the processes that cause cell death in the brain.

One study is testing the safety and effectiveness of donepezil (Aricept) for treating mild dementia in patients with Parkinson's dementia.

The drugs listed here are some of the most frequently prescribed from each class.

Gene Therapies

Researchers are also investigating possible methods of gene therapy for dementia. In one case, researchers used cells genetically engineered to produce nerve growth factor and transplanted them into monkeys' forebrains. The transplanted cells boosted the amount of nerve growth factors in the brain and seemed to prevent degeneration of acetylcholine-producing neurons in the animals. This suggests that gene therapy might help to reduce or delay symptoms of the disease. Researchers are now testing a similar therapy in a small number of patients. Other researchers have experimented with gene therapy that adds a gene called neprilysin in a mouse model that produces human beta amyloid. They found that increasing the level of neprilysin greatly reduced the amount of beta amyloid in the mice and halted the amyloid-related brain degeneration. They are now trying to determine whether neprilysin gene therapy can improve cognition in mice.


Related Interventions in CAPSIL:


Enabling Technologies

Dementia and The Home Environment

For individuals who are able to remain at home or to retain some degree of independent living, maintaining a familiar and safe environment is important.

  • The individual must be comfortable and safe if he or she is to continue to function independently.
  • Minor modifications of the home may be needed. Most important is to prevent falls and accidents. Getting rid of area rugs and putting grab bars in the shower and mats in the tub are easy important steps to make the environment safe. Sometimes, disabling the stove or using child proof knobs may be necessary to prevent cooking accidents.
  • The balance between safety and independence must be assessed often. If necessary, changes must be made to keep the individual safe.

Individuals with dementia should remain physically, mentally, and socially active.

  • Daily physical exercise helps the body and mind function. Exercise can be as simple as a daily walk.
  • The individual should engage in as much mental activity as he or she can handle. Mental activity is believed to slow the progress of some types of dementia. Puzzles, games, reading, and safe hobbies and crafts are good choices.
  • Social interaction is stimulating and enjoyable for most people with dementia. Most senior centers or community centers have scheduled activities, such as parties and clubs that are suitable for those with dementia.

It is possible to envision combining smart homes and smart devices that interact with patients (encouraging them to conduct different tasks everyday, reminding them of tasks such as exercise, gathering social events, playing mental games, etc.). Such homes and devices can allow doctors and medical staff to monitor patient progress and ensure that emergencies can be addressed promptly.


Related Enabling Technologies in CAPSIL:


References

  1. ↑ WHO 1992b. The ICD-10 classification of mental and behavioural disorders: clinical descriptions and diagnostic guidelines. Geneva: WHO
  2. ↑ 2.0 2.1 American Psychiatric Association 2000. Diagnostic and statistical manual of mental disorders, fourth edition, text revision. Washington DC: American Psychiatric Association.
  3. ↑ WHO 2001. International classification of functioning, disability and health. Geneva: WHO.
  4. ↑ 4.0 4.1 Crook T, Barrtus RT, Ferris SH, Whitehouse P, Cohen GD & Gershon S 1986. Age associated memory impairment: proposed diagnostic criteria and measures of clinical change: report of a National Institute of Mental Health work group. Developmental Neuropsychology 2:261–76.
  5. ↑ Harvey RJ, Skelton-Robinson M & Rossor MN 2003. The prevalence and causes of dementia in people under the age of 65 years. Journal of Neurology Neurosurgery and Psychiatry 74(9):1206–9.
  6. ↑ H arvey RJ, Skelton-Robinson M & Rossor MN 2003. The prevalence and causes of dementia in people under the age of 65 years. Journal of Neurology Neurosurgery and Psychiatry
  7. ↑ Chong MS & Sahadevan S 2005. Preclinical Alzheimer’s disease: diagnosis and prediction of progression. Lancet Neurology 4:576–9.
  8. ↑ http://www.alzforum.org/drg/drc/detail.asp?id=82
  9. ↑ http://clinicaltrials.gov/show/NCT00056225

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