The biggest risk factor for dementia is ageing. This means as a person gets older, their risk of developing dementia increases a lot. 

For people aged between 65 and 69, around 2 in every 100 people have dementia. A person’s risk then increases as they age, roughly doubling every five years. This means that, of those aged over 90, around 33 in every 100 people have dementia. 

Ageing is a risk factor for dementia because dementia can take a long time to develop. This is because dementia is caused by diseases that damage the brain, such as Alzheimer’s disease or vascular disease. 

It can take these diseases many years to damage the brain enough to cause the symptoms of dementia. This means that the longer a person lives, the more time there is for dementia to develop. 

Ageing is also a risk factor for dementia because an older person is likely to be coping with other changes and health conditions that can increase their risk. For example, an older person is more likely to have: 

  • high blood pressure 
  • blood vessels in the brain that are damaged, twisted or blocked 
  • a greater risk of having a stroke 
  • cells in the brain that aren’t as active as those of younger people 
  • a weaker immune system 
  • a slower ability to recover from injuries

As a person ages, they will also become more physically frail over time. Along with the changes listed above, this can make a person more likely to develop problems with their thinking and memory. 

Although older people are at a higher risk of dementia, younger people can still get it. At least 1 in 20 people with dementia developed the condition when they were aged under 65.