Causes of Alzheimer's disease

Alzheimer's disease is caused by parts of the brain shrinking (atrophy), which affects the structure and function of particular brain areas.

It's not known exactly what causes this process to begin. However,in the brains of people with Alzheimer's disease, scientistshave foundamyloid plaques (abnormal deposits of protein), neurofibrillary tangles (containing tau) and imbalances in a chemical called acetylcholine.

It's also common to have a degree of vascular damage in the brain.

Thesereduce the effectiveness ofhealthy neurons (nerve cells that carry messages to and from the brain), gradually destroying them.

Over time, this damage spreads toseveral areas of the brain. The first areas affected are responsible for memories.

Increased risk

Although it's still unknown what triggersAlzheimer's disease,several factors are known to increase your risk of developing the condition.


Age is the single most significant factor in the development of Alzheimer's disease. The likelihood of developing the condition doubles every five years after you reach 65 years of age.

However, it's not just older people who are at risk of developing Alzheimer's disease. Around1 in20people with the condition are under 65.This is called early onset Alzheimer's disease andit can affect people from around the age of 40.

Family history

The genes you inherit fromyour parents can contribute to your risk of developing Alzheimer's disease, although the actual increase in risk is small if you have aclose family member with the condition.

However, in a few families, Alzheimer's disease is caused by the inheritance of a single gene, and the risks of the conditionbeing passed on are much higher.

If several of your family members have developed dementia over the generations, it may be appropriate to seek genetic counselling for information and advice about your chances of developing Alzheimer's disease when you are older.

The Alzheimer'sSociety website has more information about the genetics of dementia .

Down's syndrome

People with Trisomy 21 are at a higher risk of developing Alzheimer's disease.

This is because the genetic fault that causes Down's syndrome can also cause amyloid plaques to build up in the brain over time, which can lead to Alzheimer's disease in some people.

Head injuries

People who have had a severe head injury have been found to be at higher risk of developing Alzheimer's disease.

Cardiovascular disease

Research shows that several lifestyle factors and conditions associated with cardiovascular disease can increase the risk of Alzheimer's disease.

These include:

  • smoking
  • obesity
  • diabetes
  • high blood pressure
  • high cholesterol

You can help reduce your risk by:

  • stopping smoking
  • eating a healthy, balanced diet
  • leading an active life, both physically and mentally
  • losing weight if you need to
  • drinking less alcohol
  • having regular health checks as you get older


Content supplied by the NHS Website

Medically Reviewed by a doctor on 21 Mar 2016