What is dementia? What are the main types and how do they differ from one another? Can we protect our brains against it?

What is Dementia? 

Dementia occurs when nerve cells in particular areas of the brain are damaged, making it more difficult for the brain to function. We often think of dementia as involving memory loss. However, dementia can affect people in different ways, depending on the affected area within each brain.

It is a progressive disorder because the damaged nerve cells cannot be regenerated or replaced. There is unfortunately no cure at present. The damage done to the brain is often visible in brain scans. 

How many people have Dementia?

In England, the number of people with dementia was estimated to be 670,000 (according to a Department of Health report in 2013) while in the UK as a whole it is estimated to be 850,000 (according to the Alzheimer’s Society in 2018).

One in three people over the age of 65 develops Dementia, of whom 60% are women.

Types of Dementia

There are different types of dementia. The Alzheimer’s Society describes the main types of dementia and their symptoms as follows:

  • Alzheimer's disease is the most common cause of dementia. During the course of the disease, the structure and the function of the brain changes, leading to the death of its cells. Symptoms, usually mild at first, can include memory loss, disorientation to time and space, difficulty organising and planning, confusion, difficulty finding the right words, difficulty with numbers and with money, changes in personality and mood and depression. 
  • Vascular dementia occurs when the blood supply to the brain is interrupted, causing cells to die within the brain. The symptoms of vascular dementia can occur either suddenly, following a stroke, or over time, through a series of small strokes. Symptoms can include slowness of thought, difficulty planning, trouble with language, problems paying attention or concentrating and mood and behaviour changes. There may also be stroke like symptoms, including muscle weakness or paralysis on one side of the body. 
  • Dementia with Lewy bodies. This form of dementia gets its name from tiny spherical structures that develop inside nerve cells. Their presence in the brain leads to the degeneration of brain tissue. Symptoms are similar to those for Alzheimer’s – plus periods of being alert or drowsy, visual hallucination and slower physical movement. 
  • Frontotemporal dementia is usually caused by damage in the front part of the brain. Here memory loss isn’t usually an issue unless the disease is in an advanced stage. Instead changes in emotion, personality and behaviour are more typical - for instance becoming less sensitive to other people’s feelings and appearing cold and unfeeling. There may also be a loss of inhibition, resulting in behaviour that seems out of character, like tactless or inappropriate remarks. Some people with frontotemporal dementia also have language problems. This may include not speaking, speaking less than usual or having problems finding the right words. 

In the later or more advanced stages of dementia, the effect on the brain can be so significant that people are unable to recognise family or friends. They may also lose the ability to speak, become less able to move without help, become incontinent and lose their appetite and lose weight. 

What are the main risk factors?

Alzheimer’s Disease International and the Mayo Clinic describe the main risk factors:

A)  Risk factors that cannot be controlled: 

  • Age. As we get older e.g. after 65 there is an increase in the risk of Alzheimer's disease and vascular dementia. However dementia can also occur in younger people.
  • Family history of dementia. This increases the risk but doesn’t mean you’ll necessarily get dementia.
  • People with Down’s syndrome, multiple sclerosis, motor neurone disease, Parkinson’s disease and Huntington’s disease can also be at increased risk of developing dementia. 

B) Risk factors that can be controlled: 

  • Alcohol. Although moderate amounts of alcohol may have a protective effect, too much alcohol use increases the risk of developing Dementia.
  • Atherosclerosis is the build-up of fats and other substances in and on your artery walls (plaques), often as a result of an unhealthy lifestyle. This can reduce the blood flow to your brain and lead to stroke and possibly vascular dementia.
  • Blood pressure. Both high or low blood pressure may increase your risk.
  • Cholesterol. High levels of ‘bad’ cholesterol i.e. low-density lipoprotein (LDL), increases the risk of developing vascular dementia or Alzheimer's disease.
  • Diabetes is another risk factor for developing Alzheimer's disease and vascular dementia.
  • High oestrogen levels. Women taking oestrogen and progesterone years after the menopause may be at greater risk of developing dementia.
  • Obesity during middle age may increase the risk of developing dementia later in life.
  • Smoking may also increase the risk of developing dementia and blood vessel (vascular) diseases. 

Can we protect the brain against dementia?

The underlying cause of dementia is unclear. However, evidence suggests that what is good for the heart is good for the brain - so a healthy diet and lifestyle may help protect the brain against dementia. This reduces the risk from the controllable lifestyle risk factors identified above.

Regular exercise, maintaining a healthy weight, avoiding fatty foods, not smoking and avoiding excessive alcohol consumption are all recommended, as is keeping mentally active into old age - for example through new interests, hobbies and skills.

One piece of encouraging news is that, according to a Medical Research Council study published in 2013, dementia rates (as a proportion of the population) are falling. This is believed to be due to action to improve heart health and also to people continuing in education for longer (what is sometimes referred to as helping build a Cognitive Reserve).


  • There are many types of dementia (of which Alzheimer’s is the most common) and they affect the brain in different ways.
  • There is currently no cure, so anything we can do to reduce the risk is to be recommended.
  • We can’t control some risks, like age or a family history of dementia.
  • However, a healthy lifestyle can reduce the risk – in particular not drinking too much alcohol, not smoking, exercise, a healthy diet, a healthy weight and education/keeping mentally active. 

Reviewed and updated by Kayhan Nouri-Aria, December 2015. Next review date November 2019.