It is particularly difficult to diagnose Alzheimer's disease because many of the symptoms are similar to other conditions.

No case of Alzheimer's disease is ever the same, as different people react in different ways to the condition. However, there are commonly three stages to the condition:

• mild,
• moderate, and
• severe.

Mild Alzheimer's disease

Common symptoms of mild Alzheimer's disease include:

• confusion
• poor memory and forgetfulness,
• mood swings, and
• problems with speech.

These symptoms are a result of gradual loss of brain function. The first section of the brain to start deteriorating is often the part that controls the memory and speech functions.

Moderate Alzheimer's disease

As Alzheimer's disease develops into a moderate stage, it can also cause:

• hallucinations,
• delusions,
• obsessive or repetitive behaviour,
• thinking you have done or experienced something that never happened,
• disturbed sleep, and
• incontinence.

The person affected may have trouble remembering very recent things. Problems with language and speech could also start to develop at this stage. This can make the person with Alzheimer's disease feel frustrated and depressed, leading to mood swings.

Severe Alzheimer's disease

Someone with Alzheimer's disease in its severe form may seem very disorientated and show signs of major confusion.

This is also the stage where people are most likely to experience hallucinations and delusions. They may think they can smell, see or hear things that are not there, or believe that someone has stolen from them or attacked them when they have not. This can be distressing for friends and family, as well as the person with Alzheimer's disease.

The hallucinations and delusions are often worse at night, and the person with Alzheimer's disease may start to become violent, demanding and suspicious of those around them.

As Alzheimer's disease becomes severe, it can cause other symptoms, such as:

• difficulty swallowing,
• difficulty changing position or moving from place to place without assistance,
• loss of appetite or loss of weight,
• increased vulnerability to infection, and
• complete loss of short-term and long-term memory.

During the severe stage, people often start to neglect their personal hygiene. It is at this stage where most people with Alzheimer's disease will need full-time care as they can do very little on their own.

Alzheimer's disease and life expectancy

One feature of Alzheimer's disease is that it affects a person's ability to look after themselves when they are ill, so a condition can develop rapidly if left untreated. A person with Alzheimer's may also be unable to tell someone if they feel unwell or uncomfortable.

Alzheimer's disease can shorten life-expectancy. This is often due to developing another condition, such as pneumonia, as a result of having Alzheimer's disease. Therefore, Alzheimer's may not be the only cause of death, but it may contribute towards it.