Alzheimer's (AHLZ-high-merz) disease is a progressive brain disorder that gradually destroys a person’s memory and ability to learn, reason, make judgments, communicate and carry out daily activities. As Alzheimer's progresses, individuals may also experience changes in personality and behaviour, such as anxiety, suspiciousness or agitation, as well as delusions or hallucinations.

The brain is perhaps the most awesome and complex example of divine engineering. In performance and ingenuity, it surpasses even the most powerful computer devised by mankind. Weighing between 1.3-1.4kg. and containing some 100 Billion neurons or nerve cells, it controls and determines who we are, what we do and how we do it.

Dementia is the progressive loss of the powers of the brain. The most common cause is Alzheimer's disease. Other kinds of dementia are vascular dementias (including multi infarct dementia), alcohol-related dementias, Lewy body dementia and Pick's disease. What all these diseases have in common is that they damage and kill brain cells, so that the brain cannot work as well as it should.

In India, approximately 3 million people have dementia. It is most common in older people but can affect people in their 40s or 50s or even younger.

We do not yet know exactly what causes dementia. Medical researchers all over the world are working to find causes and develop treatments.

Alzheimer's disease damages individual brain cells one by one, so that the brain can't work as well as it used to. A protein called amyloid builds up in deposits, called plaques, and tiny filaments in the brain cell form tangles. Much current research is trying to find out why these changes happen. Some kinds of Alzheimer's disease affecting people under 65 can be inherited. Faulty genes may cause the build up of the amyloid protein. Recent research seems to show that there may also be a genetic factor in other cases of Alzheimer's disease. However, this does not mean that someone whose parent had Alzheimer's will automatically develop the disease.

In the vascular dementias, there are problems with the blood supply to brain cells. For example, the most common type of vascular dementia is multi-infarct dementia, in which tiny strokes (infarcts) damage small areas of the brain.

Every person with dementia is different. How their illness affects them depends on which areas of their brain are most damaged.

One of the most common symptoms of dementia is memory loss. It is important to remember that everyone forgets things sometimes. Most people's memory gets worse as they get older. But when someone has dementia, they may forget the names of family members, not just of strangers. They may burn pans because they have forgotten them or forget whether they have eaten lunch. They may repeat the same question again and again and not know they are doing it.

People with dementia may lose their sense of time, losing track of which day it is or of the time of day. They may lose track of where they are, and get lost even in a familiar place. They may fail to recognise people they know well.

People with dementia may often be confused. Their ability to think, to reason and to calculate can all be damaged. They may make odd decisions and find it hard to solve problems. Handling money may become difficult as they find it harder to work out their change or lose their sense of the value of money.

Dementia can also cause personality changes. Someone who was active and energetic may become listless, someone pleasant and well-mannered may become rude and aggressive. These changes can be particularly distressing to relatives and friends as they lose the person they knew.

Gradually, over a period of years, most functions of the brain will be affected. Eventually, people with dementia will probably need help with even simple daily activities, such as dressing, eating or going to the toilet.

If someone develop dementia, their family will have to come to terms with the fact that he or she will not get better. It can help for them to have information, such as this leaflet, and to talk to someone about how they feel and what they can do. For example:

Share feelings with other members of the family or friends. Give them this leaflet and other information.

Tell the doctor about any changes.

Find out what services are available, for example form ARDSI. Try to get as much help as possible.

Talk to other people with dementia, families and carers who are facing similar problems.

Try to make life as full and enjoyable as possible. Both people with dementia and carers should try to get out and about and keep in contact with friends.

Don't just put up with new difficulties. Ask for information, help and advice to cope with problems.