Many people worry that they may be at risk of developing dementia – particularly if they have a close relative with the condition. This factsheet explains what we know about the risks associated with developing different types of dementia, and gives some advice on the steps people can take to reduce their risk. There is ongoing research in this area.
What Do We Mean by ‘Risk’ and ‘Risk Factor’?
Risk is a person’s chance of getting a disease over a certain period of time. We are all at risk of developing dementia, but some of us are more at risk than others. For example, an 80-year-old woman is more at risk of developing dementia in the next five years than a 30-year-old woman.
A risk factor is anything that increases a person’s chance of developing a condition. However, a person who has some of the risk factors for dementia will not necessarily go on to develop it, and avoiding risk factors does not guarantee that a person will be healthy – although it does make it more likely.
What are the Risk Factors for Dementia?
Researchers have discovered some important factors that affect our risk of developing dementia. These include age and genetics, but also medical history, lifestyle and environmental factors. Our risk of developing dementia depends upon a combination of these risk factors. Some of them, such as our age or genes, cannot be controlled. Other risk factors can be controlled, for example by changing our lifestyle.
The specific risk factors that have been associated with dementia are detailed below.
Age is the most significant known risk factor for dementia. It is possible to develop dementia early in life, but the chances of developing it increase as we get older. It is rare to get dementia before 65 years of age. These earlier forms of dementia tend to be very different from late-onset. After the age of 65, the risk of developing Alzheimer’s disease doubles approximately every five years. It is estimated that dementia affects one in 14 people over the age of 65 and one in six over the age of 80.
This increased risk may be due to factors associated with ageing, such as:
- higher blood pressure in mid-life
- an increased incidence of some diseases (for example, heart disease and stroke)
- changes to nerve cells, DNA and cell structure
- the weakening of the body’s natural repair systems
- changes in the immune system.
Women are slightly more likely to develop Alzheimer’s disease than men, even if we discount the fact that women are more likely to live longer. The reasons for this are unclear. One factor that has been suggested in the development of Alzheimer’s disease is a lack of the hormone oestrogen in women after the menopause. However, controlled studies have suggested that hormone replacement therapy (HRT) has no beneficial effect on the development of Alzheimer’s disease, and may even increase a person’s risk of developing the condition. It is not recommended that women take HRT as a way to reduce their risk of developing dementia.
Scientists have been aware for some time that the genes we inherit from our parents may partly determine whether we will develop specific diseases. The role of genetics in the development of dementia is still not fully understood, but researchers have made some important advances in recent years.
A number of genes have been identified that do not directly cause dementia but are thought to affect a person’s risk of developing the disease. For example, a gene called apolipoprotein E has been shown to play a part in the development of Alzheimer’s disease and vascular dementia. Risk factor genes such as this are the reason why a person’s risk of developing Alzheimer’s disease is higher if they have a close relative (parent or sibling) with the disease, compared to if there were no cases of dementia in their family.
It is also possible to inherit genes that can directly cause dementia, although these are much rarer than the risk genes. For example, there are some families in which there is a very clear inheritance of dementia from one generation to the next. Dementia-causing diseases that are hereditary (passed from parent to child) include Huntington’s disease and familial Alzheimer’s disease (a very rare form of Alzheimer’s with onset before the age of 60). In these cases what is being passed on from parent to child are specific genes that directly cause dementia. (For more information, see factsheet 405, Genetics and dementia.)
Conditions that affect the heart, arteries or blood circulation all significantly affect a person’s chances of developing dementia, particularly vascular dementia (see factsheet 402, What is vascular dementia?). These conditions include diabetes, mid-life high blood pressure and high blood cholesterol levels, mid-life obesity, heart problems (such as a heart attack or irregular heart rhythms) and stroke. Stroke is a major risk factor for dementia – it is thought that a history of stroke doubles the risk of dementia in the older population.
People who experience depression in later life or have a history of depression are significantly more likely to develop dementia. However, the relationship between depression and dementia is still unclear. Many researchers believe that depression is a risk factor for dementia, whereas others believe it may be an early symptom of the disease.
People who experience severe or repeated head injuries are at increased risk of developing dementia. It is possible that deposits that form in the brain as a result of the injury may be linked to the onset of dementia. Professional boxers sometimes develop a form of dementia known as dementia pugilistica.
Other medical conditions that can increase a person’s chances of developing dementia include Parkinson’s disease, multiple sclerosis, chronic kidney disease and HIV. Down’s syndrome and some other learning disabilities also increase a person’s risk of dementia (see factsheet 442, Rarer causes of dementia and factsheet 430, Learning disabilities and dementia).
Environment and Lifestyle Factors
Diet – Diet can affect a person’s risk of developing many types of illness, including dementia. A healthy and balanced diet that enables a person to maintain a normal body weight is likely to reduce the likelihood of developing high blood pressure or heart disease, both of which put a person at greater risk of developing dementia.
Too much saturated fat can cause narrowing of the arteries, making heart attack or stroke more likely. Heart attacks, stroke and vascular disease increase a person’s risk of developing vascular dementia.
Fresh fruit and vegetables contain many vitamins and antioxidants, which may help prevent dementia. In addition to this, low levels of vitamin D are associated with an increased risk of developing dementia. Good dietary sources of vitamin D include eggs and oily fish. The polyunsaturated fatty acids (eg omega-3 fatty acids) found in oily fish may also help reduce the risk of developing dementia.
Exercise – A good level of physical health helps to protect against many conditions, including dementia. Regular physical exercise helps to keep the heart and vascular system healthy.
Smoking – Smoking has an extremely harmful effect on the heart, lungs and vascular system, including the blood vessels in the brain. This significantly increases the risk of developing dementia.
Alcohol – Drinking above recommended levels of alcohol significantly increases the risk of developing dementias such as Alzheimer’s and vascular dementia. However, research suggests that light-to-moderate amounts of alcohol may protect the brain against dementia and keep the heart and vascular system healthy.
People who regularly drink excessive amounts of alcohol over a long period of time are at risk of developing Korsakoff’s syndrome and other alcohol-related dementias. (See factsheet 438, What is Korsakoff’s syndrome? for more information.)
Aluminium – Very low levels of many metals are present in the brain. Aluminium is a toxic metal that is common in our everyday environment. Small amounts of it are found in water and food. Although initial studies linked aluminium toxicity with Alzheimer’s disease, the link has not been proven despite continuing investigation. Importantly, there is no evidence to suggest that aluminium exposure increases your risk of dementia.
Social activity – Research suggests that people who are more socially active have a slightly reduced risk of developing dementia. Examples of social activity include visits with friends or relatives, going to the cinema, clubs, centres or places of religious worship, or volunteering. Little is known about why social activity may affect risk but research in this area is ongoing.
Mental activity – Research suggests that people who take part in mental activities (such as reading, learning and doing puzzles) are less likely to develop dementia compared with those who do not engage in these activities.
It is thought that mental activity increases the brain’s ability to cope with, and compensate for, damage. In this way, a person who often takes part in these activities will be able to tolerate a greater level of damage before symptoms of dementia are detected.
It is worth noting that ‘brain training’ games are not thought to improve ‘mental fitness’ in people under the age of 60 and there is currently no evidence that these games reduce dementia risk. However, this is a rapidly evolving area of study and research into the affects of brain training on people over the age of 60 is ongoing. Importantly, if people enjoy playing these games they should continue to do so.
How Can I Reduce My Risk of Developing Dementia?
If you are over 40 (or have a history of dementia or cardiovascular problems in your family) you should get regular blood pressure and cholesterol checks to ensure these are within recommended levels. It is also important to keep diabetes under control and seek early treatment for depression. A Mediterranean diet may help reduce risk and is relatively easy to follow.
A Mediterranean diet typically has a high proportion of fish, fruit, vegetables and unsaturated fat, and a low proportion of dairy products, meat and saturated fat. Sources of unsaturated fat include oily fish, nuts, seeds and olive oil. Adopting a balanced diet will help to manage your cholesterol, blood pressure and weight. Drink alcohol in moderation, if you wish.
Try to lead an active lifestyle combining social, mental and physical activity. Try to be physically active for at least 30 minutes, five times a week – not only will this help reduce your risk of dementia but also your risk of heart disease and diabetes. The exercise you do should be of moderate intensity. This means that you should be working hard enough to raise your heart rate and break a sweat. Examples include cycling or taking a brisk walk.
If you smoke, try to stop – this will be of huge benefit to your health in a number of ways as well as reducing your risk of dementia.
Reviewed by: Dr Ann Hale, Head of Public Health Research, Alzheimer’s Society
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