Are you worried about developing Alzheimer’s or another form of dementia in the future? If you are caring for a parent or other relative with dementia, you’ll see first-hand how devastating the condition can be. So it’s natural that, from time to time, you may feel concerned that you might develop the condition at some stage in the future. Do you have a right to be concerned?
Anyone who develops Alzheimer’s disease under the age of 65 is known to have early onset or younger onset Alzheimer’s disease. Young Dementia UK estimates that around 40,000 people in the UK have early Alzheimer’s (and most likely more people who are undiagnosed). With early onset Alzheimer’s disease, about one in ten people have a strong family pattern of inheritance.
The more common form of Alzheimer’s disease, which is usually diagnosed after the age of 65, has a more complex relationship with genetics.
Three genes
The inherited forms of Alzheimer’s disease are usually caused by a mutation in one of three genes, called APP, PSEN-1 and PSEN-2. The gene called PSEN-1 causes up to 80 per cent of what is known as ‘Familial Alzheimer’s disease’, where the disease affects generations of families. However, these mutations are rare. Fewer than one in 100 of all Alzheimer’s disease cases are thought to be caused by mutations in these three genes. However, if you do inherit a mutation in one of these genes it is likely that you will develop Alzheimer’s disease. A child of a parent with one of the three genes has a 50 per cent chance of developing it.
Alzheimer’s disease most commonly begins after the age of 65 (this is sometimes called late onset Alzheimer’s disease). The causes of this form of the condition are thought to be a mixture of genetic, lifestyle and environmental factors. A gene called apolipoprotein E (APOE) is the strongest known genetic risk factor for late onset Alzheimer’s. The gene has three forms – APOE e2, APOE e4 and APOE e3. APOE e4 is associated with an increased risk of Alzheimer’s disease.
You inherit one copy of each gene from each parent. Having at least one APOE e4 gene increases your risk of developing Alzheimer’s disease. Having two copies of APOE e4 (i.e. inheriting the gene from both parents) increases risk even further. However, not everyone who has one or two copies of this gene develops Alzheimer’s disease. If you have other versions of the gene – ApoE e2 or ApoE e3, it does not mean that you will not get Alzheimer’s disease.
There are other genes that could be risk factors for Alzheimer’s disease and some researchers believe that several genes may work in combination to influence a person’s risk of dementia. However, more research is needed in this area.
Age is a key risk
Getting older is a significant risk factor for Alzheimer’s disease and vascular dementia. Above the age of 65, your risk of developing Alzheimer’s disease or vascular dementia doubles every five years according to Alzheimer’s Society. Dementia is estimated to affect one in 14 people over 65 and one in six over the age of 80.
Vascular dementia is caused by a stroke or series or mini-strokes leading to a reduced oxygen supply to the brain. It affects approximately 150,000 people in the UK. It is less likely to be genetic, though further research is needed. Studies have shown conflicting results, as some studies show links between the gene called APOE, which can play a role in development of Alzheimer’s disease, while others don’t.
Taking care of your heart health by exercising regularly (cardiovascular exercise such as walking, running, cycling or swimming) and eating a heart healthy diet, may help to curb your risk of developing vascular dementia. A healthy heart generally means a healthy brain.
Clinical trials have shown that the genes which are recognised to be responsible for cognitive impairment in Alzheimer’s disease become less effective in those who exercise. Alzheimer’s Society believes that exercise can reduce your risk of developing a form of dementia by around 30 per cent, or Alzheimer’s disease specifically by up to 45 per cent.
We can’t control our genes, but being active and following a heart healthy diet – such as the Mediterranean diet which includes high consumption of olive oil and vegetables, may help to reduce your risk.