Alzheimer's disease is thought to be caused by a build-up of brain protein inside and around brain cells. This damages and eventually kills the brain cells.
These proteins are:
- amyloid - can build up and form plaques around brain cells
- tau - can build up and cause tangles inside brain cells
It's not known what causes this to begin. But it begins many years before symptoms appear.
There is also a decrease in the amount of chemicals that are needed to send messages between brain cells.
Over time, as the brain cells die, areas of the brain shrink. The first areas usually affected are responsible for memories. Sometimes it might be an area responsible for your vision, language, planning, problem-solving or movement.
Early symptoms of Alzheimer's disease
Risk factors for Alzheimer's
It's not your fault if you get Alzheimer's disease. Several things can increase your risk of developing Alzheimer's disease. In most cases, it is caused by a mix of these.
Age
Age is the biggest risk factor. If you're 65 and over, your chance of developing Alzheimer's doubles every 5 years.
Older people are not the only ones at risk of developing the disease.
Around 1 in 15 people with the disease are under 65. This is young onset Alzheimer's disease and it can affect people from around age 40.
Family history
For most people, the genes you inherit from your parents are not the main cause of Alzheimer's disease.
They may help increase your risk but usually not much.
But in a few families, Alzheimer's disease is inherited - a single gene passes from parent to child.
A sign of this can be when several family members over the generations develop dementia - particularly at a young age,
Non-urgent advice: Talk to your GP if:
- you're worried that your family's medical history may mean you're at a higher risk
Down syndrome
People with Down syndrome have a much higher risk of developing Alzheimer's disease. This is because the genetic difference that causes Down syndrome also causes a build-up of amyloid.
Head injuries
People who have had a severe head injury may be at higher risk of developing Alzheimer's disease. But more research is still needed in this area.
Cardiovascular disease
Cardiovascular disease involves the heart or blood vessels. Many lifestyle factors linked with cardiovascular disease can increase your risk of developing Alzheimer's disease.
These include:
- smoking
- obesity
- diabetes
- high blood pressure
- high cholesterol
These risk factors also increase the risk of vascular dementia. Many people with Alzheimer's disease also have vascular dementia.
Other things that increase your risk
There are other things that also slightly increase the risk of getting Alzheimer's disease.
These include:
- having hearing loss
- having depression that is not treated
- being socially isolated (cut off from people)
- not being active
Content supplied by the NHS and adapted for Ireland by the HSE