What is dementia?

Find out more about what dementia is and what causes it.

Who gets dementia?

Dementia can affect anybody – male or female, wealthy or poor – from any part of the world. But it doesn’t affect most people. In most cases, we don’t yet know why some people get the illnesses that cause dementia, but other people don’t.

Researchers have discovered some risk factors that increase a person’s likelihood of developing dementia. Age is the biggest risk factor: most people with dementia are older than 65. This tells us that older people are more likely to develop dementia than younger people.

Here are some more facts about dementia.

  1. Around 850,000 people in the UK are living with dementia. (There are 65.6 million people in the UK).
  1. The illnesses that cause dementia are not infectious – they don’t spread from person to person.
  1. The younger a person is, the less likely they are to develop dementia. A 65-year-old is less likely to develop dementia than an 85-year-old. When someone who is younger than 65 gets an illness that causes dementia it is called early-onset or young-onset dementia.
  1. Dementia is not a normal part of getting older. Most older people don’t have dementia, even the very oldest people who are older than 95.
  1. In the UK, about 40,000 people living with dementia are younger than 65.
  1. Certain lifestyle factors such as smoking, heavy drinking and being overweight can increase a person’s risk of developing many different illnesses, including dementia. These things don’t cause dementia – they just make a person slightly more likely to develop it.
  1. Certain genes increase a person’s risk of developing dementia. These genes don’t cause dementia – they just make a person slightly more likely to develop it.
  1. A few, very rare, types of dementia are genetic, which means that they are caused by faulty genes, and can be passed down from one family member to another. Very few people have these types of dementia and not everyone in their family will inherit the illness. If your family is affected by a rare genetic form of dementia you can read more here.
  1. Certain medical conditions increase a person’s risk of developing dementia, such as diabetes, high blood pressure and high cholesterol.

Most cases of dementia are caused by a complex mix of things, including a person’s genes, age, lifestyle and environment. By understanding the risk factors for dementia, scientists hope to find ways to prevent, treat and cure dementia in the future. You can find out more about dementia research by exploring our dementia research section

If you are worried about dementia, ask for help to find out more. Every type of dementia is different, and every person living with dementia is different, so search engines don’t always lead you to the right answers. The best people to ask are the medical professionals involved in caring for your relative.

This information was updated in December 2017 and is due for review in December 2019. Please contact us if you would like a version with references.