Illustration depicting the pathology of Alzheimer’s disease

Understanding dementia

Chances are you know someone with this condition, which most commonly affects elderly people – but how much do you actually know about dementia?

How many people in the world have dementia?

It is estimated that 44 million people worldwide are living with dementia – this number is expected to rise above 135 million by the year 2050 as more people live longer into old age.

In the UK more than 800,000 people have dementia, though less than half of them have been diagnosed according to the Alzheimer’s Society. Nearly two-thirds of people with dementia in Britain are women, and while dementia is most common in older people, it develops before the age of 65 in 2 to 5 per cent of cases.

What is it? What do we know about it?

Dementia is a set of symptoms that can include memory loss, confusion, mood changes and difficulties with thinking and speaking. These symptoms are caused by progressive damage to the brain, either from a series of strokes or a disease, the most common and well-known being Alzheimer’s disease.

Diagnosing dementia is difficult, especially when symptoms first begin to appear. Mild forgetfulness, for example, is common in normal ageing and not necessarily a sign of a developing illness. Knowing exactly which type of dementia someone has can be even more challenging – a definitive diagnosis of Alzheimer’s disease is only possible after a person has died, when certain physical changes in their brain can be seen under a microscope. This may change in the near future, however, as MRI and PET imaging techniques are being developed that can detect these changes while people are alive.

How is dementia treated?

Several drugs are available to help people with dementia, but the diseases that cause it cannot be cured. Symptoms like memory loss can be alleviated, although the drugs do not help everyone and can become less effective as the underlying disease progresses. Similarly, activities that engage people and stimulate their thinking skills can slow the loss of cognitive abilities like memory and problem solving.

Some people with dementia experience behavioural and psychological symptoms such as anxiety and depression, delusions and sleep disturbance, and agitation and aggression. These are treated in much the same way as in people without dementia, but can be particularly frightening for patients already disoriented because of dementia. They are also challenging for carers, friends and relatives to cope with, on top of seeing their loved one’s mind deteriorate.

What do scientists think is happening in the brain?

Dementia is the result of brain cells dying. The number and location of the dead cells determines what functions are lost. Our brains are able to adapt to some damage, as can be seen in people who have lost their memory or the ability to speak after a stroke, but regain these abilities through rigorous rehabilitation. Dementia is different because the brain cells keep dying off until the brain is unable to function at all.

In vascular dementia the damage is caused by a series of strokes: although these strokes are often small, sometimes imperceptible, the cumulative effect is dementia. In Alzheimer’s disease, the chain of events is not entirely clear, but the loss of brain cells appears to be linked to the appearance of two proteins called tau and amyloid beta. Less common diseases that cause dementia involve different proteins, start in different places in the brain and so present different patterns of symptoms, or result from other diseases such as AIDS or multiple sclerosis. Researchers are investigating the processes that kill brain cells and lead to dementia. As our understanding increases, the hope is that we can find ways to protect our brain cells and stop dementia as soon as it starts to appear, or even prevent it developing in the first place.

How likely am I to get it?

Some forms of dementia are hereditary – mutations in specific genes cause Huntington’s disease and rare forms of Alzheimer’s disease that usually start younger and progress more quickly than the common form. A number of other genes are associated with changes in the risk of getting dementia, so a family history of dementia is a factor in determining risk. However, the biggest risk factor for dementia is age – while about 1 in 14 people over 65 are affected by dementia, it is 1 in 6 for people over 80.

Evidence shows that we can reduce our risk by following the same advice for keeping a healthy heart – eat a balanced diet, take regular physical exercise, and do not smoke or drink too much alcohol. Keeping socially and mentally active as you age is also thought to help lower the risk of dementia.

What organisations can help?

Alzheimer’s Society


Advice line: 0300 222 1122


Alzheimer’s Research UK


Tel: 0300 111 5555


Alzheimer’s Disease International


Tel: +44 (0)20 7981 0880

Lead image:

Illustration depicting the pathology of Alzheimer’s disease, a degenerative disease of the brain characterized by the insidious onset of dementia. The condition is often marked by severe cortical atrophy and the triad of senile plaques, neurofibrillary tangles and neuropil threads.

Medical Art Service, Munich/Wellcome Images CC BY NC ND


About this resource

This resource was first published in ‘Thinking’ in July 2014.

Cell biology, Neuroscience, Psychology, Medicine, Health, infection and disease
Education levels:
16–19, Undergraduate, Continuing professional development