Causes and risk factors of dementia

Dementia can be caused by many factors, including genetics, brain changes, other health conditions and lifestyle choices. Ageing is a major risk factor, along with a poor diet, lack of physical activity, alcohol, smoking and some other medical conditions.  

This guide, written by our specialist dementia Admiral Nurses, explores the causes and risk factors of dementia.  

How do you develop dementia?

Dementia develops when there is damage to brain cells, affecting their ability to communicate with each other. As brain cells die, different areas of the brain shrink. This can lead to symptoms including:

• difficulties with remembering, thinking and communicating (cognition)
• changes in behaviour and personality

Can you reduce your risk of developing dementia?

While there is no guaranteed way to prevent dementia, there is evidence that there are some things you can do to reduce the risk. Some of these changes are easier to make than others; however, research suggests that up to one in three cases of dementia could be prevented through a healthy lifestyle such as following a balanced diet, being physically active and avoiding smoking and drinking too much alcohol.

Causes of dementia

Some causes of dementia cannot be changed, or the risk reduced. These are age, gender, ethnic background and genetic factors.

Age

The biggest risk factor for dementia is age. There are several reasons for this, including age-related changes in the brain, damage to the brain that develops over time, and the long-term effect of lifestyle factors linked to dementia.

Most people who develop dementia are over 65. Above this age, a person’s risk of developing the condition doubles roughly every five years. People over the age of 80 have a one in six chance of developing dementia, and people aged 90 and over have a one in three chance of developing the condition. However, it can occur at any age: over 70,000 people in the UK live with young onset dementia, which develops before the age of 65.

Gender

More women develop dementia than men. Two out of every three people with dementia are female, and twice as many women as men die of dementia, although this may be because women typically have a greater life expectancy.

Women are twice as likely to be diagnosed with Alzheimer’s disease, whereas men are slightly more likely to develop vascular dementia.

Ethnicity

People from certain ethnic backgrounds appear to have a higher risk of developing dementia. For example, people of Black and South Asian heritage seem to be at greater risk than White people.

This may be because Black and South Asian people are more likely to have health conditions that are linked with dementia, such as stroke, diabetes, hypertension and cardiovascular disease.

Genetics

A very small number of cases of dementia are ‘familial’ and caused by genetic mutations, such as some forms of frontotemporal dementia, Huntington’s disease and rare types of Alzheimer’s disease. However, for most people, dementia is not inherited.

Do different types of dementia have different causes?

Alzheimer’s disease is the most common form of dementia. It causes changes in the brain, in particular a build-up of abnormal proteins which form ‘plaques’ and ‘tangles’. These damage the brain cells and eventually lead to their death.

Vascular dementia is the second most common type of dementia and is caused by reduced blood flow to the brain. This could be caused by a stroke or series of mini strokes (known as transient ischaemic attacks, or TIAs), or by other conditions that damage blood vessels, such as high blood pressure, high cholesterol, heart disease and diabetes.

Lewy body dementia is caused by abnormal protein deposits in the brain, called Lewy bodies, which damage brain cells.

Frontotemporal dementia is caused by damage to the frontal (front) and temporal (side) lobes of the brain, which are responsible for personality, behaviour and language.

Risk factors for developing dementia

While there is no guaranteed way to prevent dementia, there are things you can do to reduce the risk. These are known as ‘modifiable risks’ and could potentially be reduced through people’s lifestyle choices.

Smoking

There is a strong link between dementia and smoking. This is because smoking causes blockages in the arteries, which can disrupt the blood flow to the brain. If you are a smoker, the NHS has advice on giving up.

Diet

Diets that are high in unhealthy fats, sugar and processed foods increase the risk of heart disease, high cholesterol and cardiovascular disease, which are all linked to dementia. Obesity in mid-life can contribute to these problems so it is important to try to reach or maintain a healthy body mass index (BMI).

A healthy diet may reduce the risk of cardiovascular problems and obesity, and in turn reduce the risk of dementia: the NHS has a useful guide.

Diabetes

Poorly controlled diabetes can lead to high blood sugar levels, which can damage blood vessels in the brain. If you have diabetes, it is important to ensure it is well managed. This may be through lifestyle changes (eg eating a healthy diet and taking regular exercise) and/or taking medication if prescribed.

Hypertension and heart disease

High blood pressure (hypertension), heart disease and high cholesterol levels can damage blood vessels throughout the body. If this damage occurs in the blood vessels in the brain, or if blood flow to the brain is reduced by damage to blood vessels elsewhere in the body, it can lead to a person developing dementia.

Exercise

Being physically active can reduce the risk of health problems like type 2 diabetes and heart disease, which in turn reduces the risk of dementia. The NHS website has guidance on how much activity you should aim to do.

Alcohol

There is strong evidence that drinking too much alcohol increases the risk of developing dementia. This includes regularly drinking more than the recommended maximum of 14 units of alcohol per week, and binge drinking. Please see Drinkaware for information on alcohol units and limits.

Hearing impairment and deafness

Untreated hearing loss can lead to cognitive decline in mid-life. This is thought to be due to reduced brain stimulation. We depend on being able to hear what is said or happening around us for our thought processes and memory formation.

If you have concerns about your hearing, you can book a test at a local pharmacy or optician or ask your GP to refer you to a hearing specialist (audiologist). The RNID also has an online hearing check.

Brain injury

People who have a head injury, particularly a traumatic brain injury (TBI) which affects how the brain normally functions, have a greater risk of developing dementia. This risk increases if the person has a moderate to severe head injury, or repeated head injuries over time. Older adults are more vulnerable to the long-term effects of a TBI.

The charity Headway offers information and support around TBI.

Air pollution

Growing evidence suggests that air pollution, for example from heavy traffic, is an environmental risk factor for dementia. Long-term exposure to polluted air has been linked to cognitive decline and an increased risk of developing dementia, particularly Alzheimer’s disease and vascular dementia.

Social isolation

Social isolation could increase the risk of dementia. This is because people who are lonely or isolated tend to do less physical activity, get less social stimulation, and are more likely to experience depression, which is linked to dementia. Studies have shown that people who are socially isolated tend to have changes in their brain in areas that are critical for learning and thinking.

Depression

Depression is a risk factor for dementia, and research has shown that those diagnosed with depression are more than twice as likely to be diagnosed with dementia later in life, especially if it is untreated or poorly managed.

However, depression has similar symptoms to the early stages of dementia, such as difficulty concentrating, which can affect memory. It is possible that some people diagnosed with depression who later develop dementia were actually showing the early, undiagnosed symptoms of dementia.

Socioeconomic factors

There is some evidence that people from lower socioeconomic backgrounds are at increased risk of dementia. They may have limited access to healthcare, leading to delayed diagnosis and treatment of conditions like hypertension, diabetes and high cholesterol, which are risk factors for dementia.

People from lower socioeconomic backgrounds may also experience lifestyle factors that increase their risk of dementia – such as a lack of access to exercise, difficulty eating a healthy diet and higher rates of depression.

Sleep

There is some evidence to suggest that poor sleep might be a risk factor for dementia. Insufficient sleep and poor sleep quality can lead to a build-up of proteins called amyloids in the brain, which may increase the risk of dementia. The NHS has information on improving sleep.

Medical conditions associated with dementia

Parkinson’s

Parkinson’s is a condition caused by a loss of nerve cells in a particular part of the brain, which affects the body’s regulation of movement. Most people with a diagnosis of Parkinson’s do not go on to develop dementia, but about a third do, usually in the later stages of the condition.

There are two main types of dementia related to Parkinson’s: Parkinson’s dementia and dementia with Lewy bodies. Both have similar symptoms, such as memory problems, poor concentration, difficulty with reasoning and planning, and slowed thought processes, but they develop in a different order.

Parkinson’s UK has more information.

Huntington’s disease

Huntington’s disease is a genetic disorder that leads to a protein called Huntingtin – which usually helps nerve cells develop – building up and causing damage, mainly in the areas of the brain responsible for movement, learning, cognition and emotions. Some people with Huntington’s disease go on to develop dementia in the later stages.

The Huntington’s Disease Association has more information.

Creutzfeldt-Jakob disease

Creutzfeldt-Jakob disease (CJD) is a very rare condition where the brain is infected by an abnormally shaped protein. While its cause is unknown, it is unlikely to be inherited or transmitted from person to person. Early signs of dementia in a person with CJD include minor memory problems, mood changes and apathy; these typically progress very quickly over the course of a few weeks or months.

Infections

Dementia is unlikely to be caused by a single infection, but research has shown the risk is higher in people who have, or have had:

• certain viral infections, such as herpes, HIV and Epstein-Barr
• certain bacterial infections such as Lyme disease, syphilis and gum disease (for example gingivitis and periodontitis)
• brain infections such as encephalitis or meningitis

The risk of developing dementia from an infection is low, especially from minor infections.