Dementia and Alzheimer's Disease

Definition
Dementia is an acquired impairment of intellectual function and memory without an underlying disturbance in the level of consciousness. The predominant feature is of memory loss and impairment of acquisition of new memories. There may be other defects in mental ability, such as abstract thinking, judgement, personality and language. Dementia interferes with social or occupational functioning.

Incidence/Age/Sex
The most common cause of dementia in Europe is Alzheimer’s disease with an incidence of approximately 1% over the age of 65, and 2% over the age of 80, i.e. 2 new cases every year in a group of 100 80 year olds.

Alzheimer’s disease (a specific type of dementia) is responsible for 50 - 60% of all cases; the second most common cause is multi-infarct dementia which accounts for 20% of cases and this is due to multiple small strokes. Dementia associated with Parkinson’s Disease accounts for some cases of dementia and very rarely Creutzfeldt-Jakob disease will be responsible, although this is still very rare (despite worries about BSE).

Signs & Symptoms
In the early stages of dementia it may be difficult to make the diagnosis and the diagnosis is often made by interviewing relatives of the patient. There is often a loss of social functioning, sometimes a personality change, loss of memory, particularly new memory, a loss of problem solving ability, judgement and visuospacial function. For example patients may get lost in the supermarket, on the way home from the shops or be unable to find the bathroom when visiting a relative’s house, despite having been there many times before. Standardized tests to identify dementia include the Folstein mini-mental state examination (a 30 item questionnaire designed to check reasoning, calculation and memory), or the abbreviated mental test score (a 10 point test which looks at orientation in place, time and person together with some simple memory tests). Standardized tests are particularly useful where treatment is being evaluated to give an objective view of whether a drug treatment is working.

Dementia is a diagnosis of exclusion and can be confused with brain tumour, stroke and other more rare brain diseases.

Investigations
The main investigation is an estimation of mental functioning by an experienced doctor often using the mini mental state examination, but other tests to exclude organic disorders such as brain tumour are often used. A CT brain scan is usually normal in Alzheimer’s or dementia or may show some signs of brain shrinkage. In multi-infarct dementia, signs of numerous previous tiny strokes may be seen.

Treatment
In Alzheimer’s disease there is no known treatment which will provide a cure. There are two drugs currently licensed in the U.K. which may help to slow the progression of dementia. Both of these are still undergoing large scale evaluation. The drugs currently under license in the U.K. are Donepezil and Rivastigmine. Both of these drugs are designed to increase the amount of acetylcholine in the brain as it has been found that nerve cells containing acetylcholine are much reduced in brains affected by Alzheimer’s disease. These drugs are available on the NHS but generally as part of controlled trials and many Health Authorities do not allow G.P.s to prescribe them. Not all patients with Alzheimer’s disease who take these drugs show a benefit, but many do. If no improvement is seen at 12 or 24 weeks, the drugs are usually stopped. About one-third of patients will discontinue their drugs due to side effects.

In multi-infarct dementia, attention is paid to minimizing the risk factors for stroke, such as high blood pressure, high cholesterol, diabetes and drugs such as Aspirin or Dipyridamole may be given to thin the blood in an attempt to reduce the risk of further mini strokes.

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