The exact cause of Alzheimer’s disease and most of the other dementias has yet to be established.  Many theories have been put forward.

Like most medical disorders, Alzheimer’s disease is probably caused by a combination of genetic factors and environmental influences. Most attention is currently being given to the effects of the build-up of amyloid protein in the brain. What causes this excess of amyloid is not clear. The genes responsible for amyloid production have been identified and studied extensively.

There are a few families where there is a very clear inheritance of the disease from one generation to the next. These are often families where the disease appears relatively early in life.

In the vast majority of cases, however, the effect of inheritance is small, such that if a parent or other relative has Alzheimer’s disease, your own chances of developing the disease are only a little higher than if there were no cases of Alzheimer’s disease in the immediate family.

The environmental factors that may contribute to the onset of Alzheimer’s have yet to be identified. A few years ago there were concerns that exposure to aluminium might cause Alzheimer’s disease, but these fears have largely been discounted.

Other risk factors are also being studied. Having had a head injury appears to be associated with increased risk. There are suggestions that women who have been prescribed hormone replacement therapy and people taking certain types of anti-inflammatory medication may have reduced risk.

Vascular dementia

We know a little more about the causes of vascular dementia.  Vascular dementia occurs when the cells in the brain are deprived of oxygen from an efficient blood supply.  If there is a blockage in the vascular system, or if it is diseased, blood is prevented from reaching the brain.  People with high blood pressure, high blood fats and diabetes are at greater risk of vascular disease. 

Avoiding being overweight, through a combination of healthy eating and exercise, stopping smoking and avoiding excessive alcohol intake can help prevent vascular disease.