This article was last reviewed on
This article waslast modified on 5 January 2018.
What is it?

Alzheimer's Disease (AD) is an irreversible form of dementia characterised by memory loss, a progressive decline in intellectual ability, deteriorating language and speech skills, and by personality and behavioural changes that eventually interfere with daily living. The commonest early sign is memory loss, especially for recent events. Long term memory is often preserved in the early stages of AD. Patients find it difficult to multi-task and may have disturbed sleep patterns, being wakeful during the night.

According to the Alzheimer's Society, the number of people living with dementia in the UK is about 850,000, 1.3% of the population, and it predicts that this will grow to over a million by 2025. Approximately 62% of people with dementia have Alzheimer’s disease which is the most common form of dementia. Although AD mimics some changes found in the brain as we age, it is not a normal part of the aging process. It causes nerve cell injury and death and is characterised by the build-up of senile plaques and neurofibrillary tangles (twisted protein fragments that clog nerve cells) in the brain. The destruction of nerve cells also decreases levels of acetylcholine and other neurotransmitters (chemicals necessary for communication between nerve cells) in the brain. Over time, AD results in decreased interaction between different areas of the brain. Although AD mimics some changes found in the brain as we age, it is not a normal part of the aging process. It causes nerve cell injury and death and is characterized by the build-up of senile plaques and neurofibrillary tangles (twisted protein fragments that clog nerve cells) in the brain. The destruction of nerve cells also decreases levels of acetylcholine and other neurotransmitters (chemicals necessary for communication between nerve cells) in the brain. Over time, AD results in decreased interaction between different areas of the brain.

Relationship with Ageing
The risk of having AD and other dementias increases greatly with age. About 10% to 12% of the population will have dementia by the time they are 65 years old, with the risk increasing to 50% for those who reach the age of 100. Most of the time AD is “late onset,” beginning after the age of 65, and sporadic (does not seem to be family-related). "Early onset" AD, starting before the age of 65, is more rare and more likely to be family-related. (It accounts for about 5% to 10% of all AD cases).

Risk factors
The main risk factors for developing AD are age and a family history of dementia. Other factors such as smoking, obesity, high blood pressure, diabetes mellitus and dyslipidaemia (abnormal blood cholesterol or fats) are better known as risk factors for heart disease but are also associated with AD. Women are at higher risk than men. Exercise, social and mental stimulation, a moderate intake of alcohol and a Mediterranean type diet appear to be protective.

Genetic Relationship
Although we know that people with a family history of the condition are more likely to develop AD, the genetics of the common type of AD are not well understood.

We know that there are a few very rare cases, associated with early onset Alzheimer's disease, where there is a clear genetic inheritance within specific families. These are families where members inherit genetic faults on chromosomes 14, 1 or 21. The genes affect proteins in the brain called presenilin 1, presenilin 2 and amyloid precursor protein respectively. Children of affected individuals have a 50% chance of inheriting the condition. All those who inherit the gene will go on to develop Alzheimer's.

Another gene, ApoE, has been associated with an increased susceptibility to late onset AD. This gene directs the production of apolipoprotein E, a protein that forms part of the body’s lipoproteins (such as HDL cholesterol) and is involved in lipid transportation and clearing dietary fats from the body. The ApoE gene normally exists in three forms: e2, e3, and e4. Everyone has two copies of the ApoE gene, in some combination of the three forms. People who have two copies of the e4 variant have a fifteen fold increased risk of AD.

There is a higher incidence of Alzheimer’s Disease in people with Down's Syndrome and in families who have siblings and/or parents with AD and/or several generations of family members with AD. Researchers have been aware of a connection between Down's syndrome and Alzheimer's disease since the 1940s. People with Down's syndrome, who inherit an extra copy of chromosome 21, develop the same 'plaques' and 'tangles' in their brains as people with Alzheimer's disease.

 

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About Alzheimer's Disease
  • Tests

    There are no laboratory tests available that will positively diagnose Alzheimer’s Disease. Currently, the only definite diagnosis of AD is to examine a section of the patient’s brain tissue under a microscope; this is rarely undertaken during life. Pathologists look for senile plaques and neurofibrillary tangles characteristic of AD. Since plaque and tangle formation is also seen in normal aging, the sample must be compared to a control sample (normal, non-AD brain tissue) from a person the same age as the patient.

    Some studies have suggested that looking at changes in specific substances in cerebrospinal fluid (CSF), such as tau protein or amyloid-beta proteins could help to make a diagnosis or monitor treatment. More research is required to see if these techniques could be useful in routine care.

    Doctors currently use a variety of tests and procedures to rule out other causes for dementia, such as anaemia, infection, disorders of the thyroid gland, vitamin B12 deficiency and mini-strokes, before diagnosing patients as having AD.

    In some patients, magnetic resonance imaging (MRI) scans are used to look for evidence of trauma, tumours or stroke that could be causing dementia and to look for brain atrophy (shrinkage) that is typical but not diagnostic of Alzheimer’s Disease (it may also be seen in many other brain disorders).

    When a patient presents with symptoms of dementia, the doctor will evaluate his or her personal and family history (preferably of several generations); perform a physical examination; determine the age of onset, and undertake neuropsychological tests to measure his or her memory, language skills, and other cognitive functions. These tests include the Mini-Mental State Examination and the Montreal Cognitive Assessment scores. They can be repeated at intervals to determine how rapidly the disease is progressing. A hallmark of Alzheimer's Disease is that its appearance is a subtle, progressive decline in function. If the onset of the patient’s problems is abrupt or happened in a step-wise fashion, then the cause is most likely something other than AD.

  • Treatments

    There is currently no prevention or cure for Alzheimer’s Disease. Patients may live with AD for 1 to 25 years, but the average is 8 to 10 years. Treatment consists of attempting to slow the progression of the disease, easing symptoms, managing behavioural issues, and providing the patient and carers with support and education. Early in the disease, those with AD may be able to live fairly normal lives with small amounts of assistance, such as memory aids and a structured environment. This is the time when the patient can make plans and participate in decisions about their future care.

    Early diagnosis of AD may allow some people to receive moderate benefit from cholinesterase inhibitors, drugs that preserve intellectual ability by enhancing the function of acetylcholine (a neurotransmitter in the brain that allows nerves and parts of the brain to communicate with each other). Drugs available in the UK include galantamine , donepezil and rivastigmine. Memantine is another type of medication that works by protecting the brain from excess glutamate but is used in the later more severe stages of AD. The patient’s other drugs will be evaluated, and those that may worsen confusion, such as central nervous system depressants, antihistamines, sleeping pills, and analgesics will be stopped whenever possible.

    Throughout the progression of AD, antidepressants and other drugs may also be used in small quantities, along with environmental modification (making the home environment safer and more familiar), to alleviate personality and behavioural issues such as depression, agitation, paranoia, and violence, and to make the patient more comfortable.

    Research studies into the protective and therapeutic influences of substances such as nonsteroidal anti-inflammatory drugs (NSAIDs), oestrogen, and antioxidants like Vitamin E are on-going. Early results suggest that Vitamin E may be protective but that the others have little effect. None are recommended for routine use because the benefits are outweighed by the potential risks.

  • Frequently Asked Questions

    1. What are some other causes of confusion, memory lapses, and cognitive decline?
    Occasional forgetfulness is normal and should not be a cause for concern unless it significantly increases in frequency or interferes with daily living. Some of the causes of cognitive decline, besides AD, include nutritional deficiencies, such as vitamin B12 deficiency; metabolic conditions, including diabetes, electrolyte imbalance, hypertension (high blood pressure), and kidney, liver, and thyroid disorders; structural disorders like brain tumours, head injuries, normal pressure hydrocephalus, and vascular dementia; degenerative disease, including age-related cognitive decline, diffuse Lewy body disease, Huntington's chorea disease, Parkinson's disease, and Pick's disease; infectious diseases like HIV/AIDS, Creutzfeldt-Jakob, meningitis, encephalitis, and syphilis; and still other causes, such as anxiety, depression, heavy metal poisoning (for example, lead poisoning), medication interactions and side effects, overmedication, and seizures.

    2. Is there a way to get involved in research efforts related to Alzheimer’s Disease?
    Yes, by supporting the work of Alzheimer's Research UK, a national Alzheimer's research network. For more information, visit Alzheimer's Research UK.

    3. Is there a link between Mad Cow Disease and Alzheimer’s Disease?
    There is no evidence at this time of any connection between Mad Cow Disease and Alzheimer's even though the symptoms may appear similar.