advertisement
15 September 2011

Alzheimer's disease

Alzheimer’s disease is marked by a progressive degeneration of brain tissue, causing dementia.

0

Summary

  • Alzheimer’s disease is marked by a progressive degeneration of brain tissue.
  • It is the most common form of dementia in older adults and entails the eventual loss of memory and the ability to think and do.
  • Initially the progression is slow and the disease may be mistaken for the normal ageing process.
  • There is no cure.
  • The goal of treatment is to slow the progression of the disease and manage symptoms.

Description

Alzheimer's disease – after heart disease, cancer and stroke – is the fourth leading cause of death in the United States of America and the most common form of dementia.

This incurable brain disease was named after the German physician Alois Alzheimer, who identified it in 1907. The disease, marked by a progressive degeneration of brain tissue, primarily affects people over the age of 65. In such cases it is known as late-onset Alzheimer’s disease. It has also been reported among people in their 50s, 40s and – rarely – 30s (early onset). Nearly all people with Down syndrome will develop this disease if they live into their 40s.

Eventually, people suffering from Alzheimer’s disease lose the ability to think, reason and co-ordinate movement, and become incapacitated over the course of five to eight years. From the age of 60 one’s risk for developing  Alzheimer’s disease or a related dementia doubles every five years. At 60 years of age the risk is approximately 1 in a hundred, by 65 years 1 in 50,  70 years 1 in 20 , etc. By 85 and older, approximately 2 out of every 5 people have some form of dementia.

Causes

The causes of Alzheimer’s disease are not fully known and scientists continue to investigate this area. So far, research into the causes of this brain disease has found two main forms of neural damage or abnormalities that can be linked to the disease and its progression.

Genetic studies have shed new light on possible causes of Alzheimer's disease, but these must be researched further. Aluminium and zinc as causes were the topics of controversial studies and are discussed in less detail.

Tangled nerve cell fibres (neurofibrillary tangles)

Microscopic study of the brain of a person who has died from Alzheimer’s disease reveals tangled nerve cell fibres in certain areas of the brain. (Nerve cell fibres are typically found inside nerve cells.) As the nerve fibres become tangled, protein deposits called plaques build up in the affected tissue. A protein called tau is found in the tangles. Scientists are not sure how these neurofibrillary tangles are formed, but they are characteristic of the condition.

Senile or neuritic plaques

These patches are situated outside the nerve cells and are surrounded by dying neurons (nerve cells). The plaques contain a sticky protein, beta amyloid, which causes malfunctioning of nerve cells that eventually results in death of these cells. The plaques are made of amyloid precursor protein (APP) molecules, which are usually essential components of the brain. Plaques are formed when an enzyme takes APP apart at a specific location and leaves the fragments (beta amyloid) in brain tissue, where they deposit abnormally. The presence of neuritic plaques may be linked to a reduction in acetylcholine, an important chemical that is instrumental in relaying messages in the brain.

Genetics

The association between Down syndrome and Alzheimer's disease has led scientists to look for genetic factors on chromosome 21, the chromosome involved in Down syndrome. Chromosomes are found in each cell in the body and carry the hereditary information (genes). Other chromosomes that scientists have studied in relation to Alzheimer’s disease include chromosomes 14 and 19. The study of chromosome 19 is the most significant. It was on this chromosome that scientists discovered the ApoE-e4 gene, a well-known marker for heart disease that is commonly found in people who developed Alzheimer's disease at age 65 years or older. The gene was less likely to be found in people who did not have Alzheimer's disease. These findings led scientists to believe that people with this gene might be more susceptible to Alzheimer's disease, although it is not a definite indicator.

Aluminium

Some researchers found increased levels of aluminium, mercury and other metals in the brains of victims of Alzheimer’s disease. This led to a controversial theory suggesting that the ingestion of small particles of one of these metals, especially aluminium, may lead to the development of Alzheimer's disease. However, much more research is necessary to determine whether aluminium build-up is a cause or a result of Alzheimer’s disease and to better understand the exact role of this and other metals in the development of the disorder.

Zinc

Zinc is the focus of another controversial theory about the possible causes of Alzheimer's disease. Studies suggesting a link between zinc and improved mental alertness in the elderly led scientists to give Alzheimer's disease patients zinc supplements in a 1991 study. However, after only two days the patients’ mental abilities deteriorated rapidly. A few years later, laboratory tests revealed that zinc could make proteins form clumps similar to the plaques found in the brains of Alzheimer's disease sufferers. This needs to be further investigated, as scientists are not sure yet whether the plaques actually cause the disease or whether they are a result of it.

Symptoms

Symptoms of Alzheimer's disease vary greatly from person to person, but a few general symptoms can be distinguished. The symptoms are closely related to the various stages of the disease.

Early stage

During this period, usually the first two to four years, symptoms are slow and gradual and can be mistaken for the normal ageing process. Early signs of memory loss characterise this period and may include forgetting names or events. Affected people may also have difficulty following directions and be disoriented. Changes in their normal behaviour and personality can be noted and they are no longer able to perform routine tasks.

Later stage

In this stage, people may suddenly lose their inhibitions, no longer be able to solve simple problems and have trouble with figures. Adapting to simple changes becomes a problem and the afflicted may become confused and disoriented, not knowing what month or year it is and not being able to describe accurately where they live or recall correctly the name of a place recently visited.

Emotionally, Alzheimer sufferers become increasingly suspicious and paranoid. They can no longer control their anger, frustration or inappropriate behaviour and become increasingly quarrelsome, irritable and agitated. They can also no longer dress appropriately and neglect their personal appearance.

Final stage

Severe impairment of intellectual abilities are typical of the final stage of the disease. Physical functioning deteriorates and sufferers become incontinent (unable to control bowel and bladder function). They can no longer engage in conversation, are erratic and inattentive and appear uncooperative. In the final stage they become incapable of looking after themselves and become bedridden or wheelchair-bound. They are often not able to feed themselves and have to be fed. Death is usually the result of pneumonia or another illness that occurs when health has deteriorated severely.

Prevalence

The prevalence of Alzheimer's disease is closely linked to age and dramatically increases with age. 10% of all persons older than 65 years have Alzheimer's disease and 50% of those older than 85 years.

Course

The average duration of the illness is  six to eight years, but it can run its course in just a few months or take as long as 20 years.

Risk Factors

Increasing age is the main risk factor for Alzheimer's disease.

Other risk factors include a family history of dementia and previous head trauma.

When to see a doctor

If a family member or friend displays signs of Alzheimer’s disease over time, you must call your doctor. The person may have a lack of insight that is characterised by not knowing that he or she has the disease and denying the assistance of other people. Thus, the affected person may have to be persuaded to visit a doctor for help.

Diagnosis

It is most important that a doctor should diagnose Alzheimer’s disease, as many other treatable conditions (such as hypothyroidism, vitamin deficiency, hypoglycaemia, anaemia and depression) have symptoms similar to Alzheimer's disease. Other causes of Alzheimer's disease-like symptoms include an adverse reaction to prescribed medicine or a harmful combination of medicines.

To check whether a person has Alzheimer’s disease, the doctor will first do a memory test and then a physical examination in order to eliminate other possible causes of the patient’s mental impairment. Therefore the clinical diagnosis of Alzheimer's disease is a diagnosis by exclusion. Verbal tests, as well as interviews with family members may be the next step, although these methods will not yield definitive results.

Other tests used to diagnose possible Alzheimer's disease could include

  • Blood tests
  • Brain scan
  • Electrocardiogram (ECG, a recording of the electric activity of the heart)
  • Electroencephalogram (EEG, a recording of the electric activity of the brain)

Brain scans can provide valuable information about the brain. These include

  • Computerised axial tomography (CAT) – to exclude disorders with similar symptoms to Alzheimer's disease. CAT scans may reveal changes that are characteristic of the disease.
  • Magnetic resonance imaging (MRI) – this type of scan provides more detailed information about physical structure and deeper brain tissue near bone and may add diagnostic information. Functional MRI (fMRI) can provide information on the functioning of the brain including which areas may be underfperforming.
  • Positron emission tomography (PET) – a new instrument that researchers can use to learn more about the brain. It can provide information about blood flow in the brain, metabolic activity and the way that specific receptors are distributed in the brain. More recently it can be used to identify and quantify both neurofibrillary tangles and plaques with mildly radio-active substances that bind to these.
  • Single photon emission computerised tomography (SPECT) – another instrument available to researchers to help them look for the abnormalities typical of Alzheimer’s disease.

Treatment

There is no cure for Alzheimer's disease. Certain medicines can improve memory and slow the progression of the disease in the early stages, and others can alleviate mood changes and other behavioural problems associated with the disease. The goal of treatment in Alzheimer's disease is to manage the symptoms as far as possible.

Medication

  • Aricept (donepezil hydrochloride), Exelon (rivastigmine) and Reminyl (galanthamine) work by slowing the breakdown of acetylcholine, the chemical that helps the neurons communicate with one another. It may help improve memory to some extent in people with mild to moderate Alzheimer’s disease.
  • Ebixa (memantine) blocks NMDA glutamate receptors in the brain providing neuroprotective effects from toxic levels of glutamate.  It has been shown to slow the deterioration of the illness and to improve activites of daily living.
  • A number of drugs can alleviate specific symptoms. Antidepressants, anti-anxiety, mood-stabilising and other medications (e.g. anti-psychotics) can be prescribed.

Home

The immediate environment of the Alzheimer's disease sufferer can play an important role in helping him or her cope with the disease. It is important that family members who are looking after the person in the final stages of the illness take note of this and modify the surroundings to reduce stress from environmental factors.

Family members of people with Alzheimer's disease can do the following

  • Provide balanced nutrition and plenty of fluids.
  • Keep pills and poisons away.
  • Keep instructions simple and short.
  • Promote a feeling of safety. Keep the living environment familiar and stable by sticking to a routine.
  • Keep visual clues to time and place, such as calendars, clocks and pictures of the season.
  • If you have to leave the house, leave reminder notes and simple directions which your relative can easily follow and remember.
  • Label objects.
  • An ID bracelet with a phone number is indispensable for people with Alzheimer's disease because they are inclined to wander and get lost.
  • As long-term memory is better than short-term memory in the early stages of the disease, the person may enjoy reminiscing about pleasant past memories. Use family photo albums, old magazines and favourite family stories to bring these memories to the fore.

Looking after an Alzheimer's disease patient can be an emotionally draining experience for family members. If you are caring for someone with Alzheimer's disease, relief from ordinary day-to-day chores in the home may help you cope with the deterioration of a loved one. The role of support groups and social workers cannot be overemphasised in this regard.

Prevention

Prevention of Alzheimer's disease is very difficult, as there is no known cause. Although genetics is a possible cause, this does not mean that if Alzheimer's disease has claimed some members of a family that all the other members will develop it.

If you are concerned about developing Alzheimer’s disease, the best thing to do is to have a healthy lifestyle. Eat a balanced diet and exercise regularly to keep your body, including your brain’s nerve cells, in shape. Studies suggest that highly educated or mentally active older people are less likely to fall prey to this debilitating disease. If possible, avoid cigarette smoke and air pollution. Avoiding these substances minimises your exposure to free radicals (highly reactive molecules) that have been implicated in the formation of plaques.

High doses of Vitamin E and Ginkgo biloba are no longer recommended.

Omega-3 fatty acids may have some preventative role in Alzheimer’s disease.

Do not limit your daily intake of zinc in accordance with the theory that explores a link between this mineral and Alzheimer’s disease. Zinc is an important mineral and, although you should not take an overdose of it, restricting your intake to below the recommended daily allowance (15 mg for men and 12 mg for women) will do more harm than good.

Social interaction may be protective, while alcohol consumption, particularly in excess has been identified as neurotoxic.

A recent study links exercise to improvements in memory for those with early short-term memory problems.  It was discovered that those who exercised increased the size of their hippocampus (an important part of the brain for memory). Scientists have linked this to increased levels of Brain-derived Neurotrophic Factor, an important chemical for healthy brain function.

Previously reviewedby Dr Frans Hugo, MBChB, M.Med Psychiatry

Reviewed by Dr Michael S. Mason, MB ChB,  FC Psych (South Africa), Consultant Psychiatrist In Private Practice at Panorama Psychiatry and Memory Clinic, September 2011 

Post a question to Cybershrink

 
advertisement

Get a quote

advertisement

Read Health24’s Comments Policy

Comment on this story
0 comments
Add your comment
Comment 0 characters remaining

Live healthier

Knee pain relief »

Knee injuries Test your knee pain knowledge Symptoms of knee pain

Do you suffer from knee pain?

Do you suffer from recurrent knee pain? It could be osteoarthritis...

Vitamin wise »

Vitamins for HIV What to eat for vitamin B? Cut down on vitamins

Get your vitamins right

Find out which vitamin to use for which condition. Ask our Vitamin expert.