3. Who gets Alzheimer's disease?
Most people who develop Alzheimer's disease do so after the age of 65, but people under this age can also develop it. This is called early-onset Alzheimer's disease, a type of young-onset dementia. In the UK there are over 40,000 people under the age of 65 with dementia.
Developing Alzheimer's disease is linked to a combination of factors, explained in more detail below. Some of these risk factors (eg lifestyle) can be controlled, but others (eg age and genes) cannot.
Age is the greatest risk factor for Alzheimer's. The disease mainly affects people over 65. Above this age, a person's risk of developing Alzheimer's disease doubles approximately every five years. One in six people over 80 have dementia.
For reasons that are not clear, there are about twice as many women as men over 65 with Alzheimer's disease. This difference is not fully explained by the fact that women on average live longer than men. It may be that Alzheimer's in women is linked to a lack of the hormone oestrogen after the menopause.
Many people fear that the disease may be passed down to them from a parent or grandparent. Scientists are investigating the genetic background to Alzheimer's. There are a few families with a very clear inheritance of Alzheimer's from one generation to the next. In such families the dementia tends to develop well before age 65. However, Alzheimer's disease that is so strongly inherited is extremely rare.
In the vast majority of people, the influence of genetics on risk of Alzheimer's disease is much more subtle. A number of genes are known to increase or reduce a person's chances of developing Alzheimer's. For someone with a close relative (parent or sibling) who was diagnosed with Alzheimer's when over 65, their own risk of developing the disease is increased. However, this does not mean that Alzheimer's is inevitable, and everyone can reduce their risk by living a healthy lifestyle.
People with Down's syndrome are at particular risk of developing Alzheimer's disease, because of a difference in their genetic makeup.
Health and lifestyle
Medical conditions such as diabetes, stroke and heart problems, as well as high blood pressure, high cholesterol and obesity in mid-life, are all known to increase the risk of both Alzheimer's disease and vascular dementia. Anyone can reduce their risk by keeping these under control. Depression is a probable risk factor for dementia; getting it treated early is important.
People who adopt a healthy lifestyle, especially from mid-life onwards, are less likely to develop Alzheimer's disease. This means taking regular physical exercise and keeping to a healthy weight, not smoking, eating a healthy balanced diet and drinking only in moderation.
Leading an active lifestyle that combines regular physical, social and mental activity will help to lower risk.