Dementia covers a range of symptoms that interfere with your ability to function normally. By the time you get to middle age it is not unusual to start worrying that any sign of forgetfulness means you are developing dementia.

What is dementia?

There are different types of dementia, but the most common are Alzheimer's disease (in which the brain is disrupted by clumps of protein that build up and damage brain cells) and vascular dementia (caused by blood vessel damage resulting in an inadequate circulation of oxygen to the brain).

What are the symptoms?

Dementia becomes increasingly common over the age of 65 and people often worry about developing it just because they can't remember where they put their car keys. Yet the early signs are often subtler. Symptoms can include struggling to find the right name for something or needing to be told arrangements again and again.

Someone with dementia may find it hard to concentrate and be unable to use household items, such as microwaves. They may forget what day it is or what their routine is. Another early sign is constantly losing things – to the extent that they accuse someone of taking their belongings. People with early dementia can be grumpy and withdraw from social activities. They can also seem depressed or distracted and have mood swings. In the early stages you may only suspect something is not quite right.

How is it diagnosed?

Dementia in its early stages can be difficult to diagnose. Some medical conditions and drugs mimic dementia. The most common test used is the mini mental state examination asking a series of questions such as: "Do you know what day of the week it is, the month and the year and the time of day?" The person may be asked to name familiar objects and to count backwards by subtracting a series of numbers. My father, who had dementia, was always asked: "Who's the prime minister?" The answers are marked out of 30, with 25 or more being normal.

What are the risk factors?

Getting older and having people in your family who have had dementia increases your own risk. Having high blood pressure increases your risk of vascular dementia as does drinking heavily and smoking.

Can it be prevented?

There is some evidence that if you are mentally and physically active and if you get out of the house, have friends you socialise with, read, play an instrument, take courses, play bridge or golf, or walk regularly, you are less likely to develop dementia.

Can it be treated?

The latest draft guidance from Nice says that some drugs improve the symptoms of Alzheimer's disease. In some cases these drugs can slow the progression of the disease, but there is no cure. Acetylcholinesterase inhibitors work by preventing the breakdown of a chemical in the brain called acetylcholine (examples include Aricept and Exelon) that's involved in messaging between nerve cells. Another drug called Ebixa blocks a chemical called glutamate which is released and damages brain cells in Alzheimer's disease.

When should I see my doctor?

If you think you or someone you are caring for is developing symptoms of dementia it is worth getting tested.