What causes Alzheimer’s disease?
Alzheimer’s disease is caused by a loss of nerve cells in regions of the brain responsible for memory (known medically as the cerebral cortex). As the disease progresses this loss gradually affects those parts of the cortex that deal with almost all aspects of behaviour, although certain areas (those dealing with the processing of vision and the control of normal movement) are spared.
How many people are affected?
When Alzheimer’s disease was first identified in 1907, it was considered a rare disorder. Today, Alzheimer’s disease accounts for up to two thirds of all cases of dementia – and affects over 500,000 people in the United Kingdom. There are about 60,000 new cases of AD each year in the UK, and this number is expected to rise to around 100,000 by the year 2040.
Although this bald statement indicates how many people have the disease, it is not a true indication of how many people are affected. Around 80% of AD sufferers live at home, and many of these people are cared for by informal carers – usually partners. About half of the carers for people with AD are themselves over 70 years old.
What are the symptoms of AD?
Alzheimer’s disease usually begins gradually, causing a person to forget recent events and to have difficulty performing some familiar tasks. This is unlike the memory lapses that can occur in older people. While the ordinarily forgetful person will temporarily forget parts of an experience (and remember them later), a person with AD is likely to forget the entire experience (and will rarely remember anything about it at a later time).
Most people have the experience of momentarily forgetting the name of the person they are talking to, but people with AD lose the entire context of what they are doing – and this can mean that memory losses in AD can be quite startling. In the middle of a conversation, people with AD may suddenly forget what topic they are talking about – or, quite literally, who they are talking to. Understandably, confusion is also a symptom of AD.
How is Alzheimer’s disease diagnosed?
There are no simple tests for Alzheimer’s disease. The diagnosis is usually arrived at by a process of elimination, which may involve:
- a thorough medical history and physical examination
- a psychological assessment or questionnaire
- an assessment of how well memory is functioning
- a brain scan
Because the symptoms of AD are diffuse and difficult to quantify, the doctor making the diagnosis will often need to take a history from a partner, or somebody who knows the patient well. The reason for such an extensive diagnostic procedure is that memory lapses or confusion can be caused by conditions such as chest or urinary infections, constipation, thyroid problems, stress, depression and can also be the side effects of certain drug treatments.
Is Alzheimer’s disease an inevitable part of ageing?
The risk of developing Alzheimer’s disease increases with age – it is present in 5% of people over the age of 65 and 25-30% of people over 85 years. However, most researchers would resist the temptation to categorise AD as an inevitable part of normal ageing. There are many sprightly 90 year olds who do not suffer from Alzheimer’s, and there are occasional cases where Alzheimer’s disease develops in people as young as 40 years old. If Alzheimer’s disease develops before the age of 65 years it is referred to as early onset AD. There are about 17,000 people with early onset dementia in the United Kingdom the majority of which is AD.
Is Alzheimer’s disease genetic?
Research has identified three genes that are responsible for the rare early onset Alzheimer’s disease, and it is probable that other genes causing early familial AD remain to be discovered.
The genetics of late onset AD is very different, and probably more complex. Research has identified two genes that affect the risk of developing AD. However, there are other strands of research which suggest that the risk can be affected by a variety of non-genetic influences including:
Hormones
Several studies have observed that women taking HRT are less likely to develop AD. However the evidence on the therapeutic effect of HRT is far from clear – a recent trial of oestrogen replacement therapy in women who already have AD proved negative. The triallists concluded that HRT should not be used to treat AD that is already in existence, but the question remains: does HRT taken earlier in life prevent AD from developing? A major ten year study, involving 22,000 women is now underway to clarify this point.
Diet
Results from various different strands of research have started to highlight the potential role of diet in the development or progression of AD. Japanese living in Hawaii have a higher risk of developing AD than those living in Japan, suggesting a dietary or environmental factor. A two year study has shown that very high doses of vitamin E can significantly prolong functioning in people in the early to middle stages of AD, but without improving the memory problems, and further trials are underway. Work in Oxford has shown that patients with AD have low levels of folic acid in the blood and this has been confirmed in the USA; trials are being planned to see if dietary folic acid can help slow the progression of the disease.
Is it possible to live with Alzheimer’s disease?
In the early stages of Alzheimer’s disease there are few problems presented to people continuing to live their lives as they did previously. Most people choose to remain in familiar surroundings for as long as possible, and make adjustments to their everyday lives to compensate for the effects of the disease. These can include establishing routines or habits to compensate for failing memory, or modifying the home in preparation for a time when their mobility or co-ordination becomes impaired. Most people choose to re-organise their finances when they are diagnosed.
After the shock of their diagnosis has subsided, many people start to focus on the activities they can still enjoy, even though their lives might be more limited than before. “In many ways the diagnosis opened my mind – and it was an impetus for both of us to make the most of life. We made sure we took more holidays, and valued the time together as a family.” Pat Boyes, wife of former MP Roland Boyes, who has Alzheimer’s disease.
The progression of Alzheimer’s disease
AD has an insidious onset, with a gradual decline in memory and other aspects of functioning. There may be subtle changes in personality, with a reduction in confidence and range of interests. More complex aspects of daily living – like cooking a meal, dealing with finances, or driving – prove increasingly difficult for people as the disease progresses. Language problems may occur, particularly affecting word fluency, and cause difficulty in finding the right words or with following conversations. These language difficulties are sometimes quite prominent even in the early stages of the disease. As AD progresses there are increasing changes in behaviour and in more personal activities of daily living, such as dressing and eating. Loss of bladder, and later, bowel control is common.
The rate of decline is not necessarily constant, being slower in the early and advanced stages of the disease compared to the middle stage. People with any type of dementia have a lower survival rate, and the average duration from onset of symptoms to death is eight to 10 years.
Are there any treatments for Alzheimer’s disease?
Over the past 30-40 years, numerous drugs have been suggested for use in AD or other dementias. Until recently, most drugs had not been evaluated properly, there are now several drugs which are either at the clinical trial stage, or are available on prescription. All of these the drugs are designed to provide symptomatic relief – a temporary improvement in memory or thinking abilities – for people in the mild to moderate stage of the disease.
The two drugs that are available on prescription are donepezil (called Aricept) and rivastigmine (called Exelon). Although they are relatively new, studies have shown that these drugs can give an overall improvement in the patient’s ability to function in everyday situations. There is also evidence that donepezil can reduce the apathy and agitation that are sometimes experienced by people with AD.
There are several drugs that are currently at the clinical trial stages. The results of a trial of galantamine (called Reminyl), derived from a substance present in Caucasian snowdrops, have shown that it may improve memory performance and the behavioural symptoms of AD.
The results of recent research are providing substantial hope that a new vaccine may be developed for AD. The vaccine is thought to stimulate the body to mount its own immune defence against protein deposits which impede and kill nerves in the brain, although scientists do not know whether they are a cause or a result of the illness. The vaccine is now entering clinical trials.
Studies have suggested that the progression of Alzheimer’s disease may be delayed in those taking non-steroidal anti-inflammatory drugs (NSAIDs), with the incidence in these patients described as being cut as much as in half. There are currently trials underway to verify these claims.
Gingko biloba is a plant extract whose main actions may be as a vasodilator and an antioxidant. Although there is some evidence of positive effects for patients with Alzheimer’s disease, the trials have not been as rigorous as is normal in the testing of pharmacological agents. Further carefully controlled studies are necessary to determine the level of benefit and to clarify dosage.
Is there anything else to help people with Alzheimer’s disease?
Other drugs are sometimes prescribed for the symptoms of dementia, such as depression, restlessness, delusions and hallucinations. These include tranquillisers, antidepressants and anxiety-relieving drugs.
In addition to the drug therapies that are commonly dispensed to help sufferers of AD, there are also a number of approaches that help people maintain contact with the outside world. Occupational Therapists have a repertoire of techniques, including music and art therapy, which help dissolve the feelings of frustration that are often experienced by people in the advanced stages of the disease.
