Risk factors for dementia

The biggest risk factor for dementia is ageing. This means as a person gets older, their risk of developing dementia increases a lot. 

For people aged between 65 and 69, around 2 in every 100 people have dementia. A person’s risk then increases as they age, roughly doubling every five years. This means that, of those aged over 90, around 33 in every 100 people have dementia. 

Ageing is a risk factor for dementia because dementia can take a long time to develop. This is because dementia is caused by diseases that damage the brain, such as Alzheimer’s disease or vascular disease. 

It can take these diseases many years to damage the brain enough to cause the symptoms of dementia. This means that the longer a person lives, the more time there is for dementia to develop. 

Ageing is also a risk factor for dementia because an older person is likely to be coping with other changes and health conditions that can increase their risk. For example, an older person is more likely to have: 

• high blood pressure 
• blood vessels in the brain that are damaged, twisted or blocked 
• a greater risk of having a stroke 
• cells in the brain that aren’t as active as those of younger people 
• a weaker immune system 
• a slower ability to recover from injuries

As a person ages, they will also become more physically frail over time. Along with the changes listed above, this can make a person more likely to develop problems with their thinking and memory. 

Although older people are at a higher risk of dementia, younger people can still get it. At least 1 in 20 people with dementia developed the condition when they were aged under 65. 

There are certain genes that can affect a person’s chances of getting dementia. These may be passed down (inherited) from a parent. There are two types of these genes: ‘familial’ genes and ‘risk’ genes.

What are 'familial' genes?

Familial genes will definitely cause dementia if they are passed down from a parent to a child.

However, if one parent has a familial gene, their child will have a 1 in 2 chance of inheriting it and developing dementia – usually when they are in their 50s and 60s.

Familial genes are very rare for most types of dementia. However, these genes may be the cause of around 1 in 3 cases of frontotemporal dementia, which is a less common type of dementia.

What are 'risk' genes?

Risk genes increase a person’s chances of developing dementia. They are much more common than familial genes. However, unlike familial genes, risk genes do not always cause a person to develop dementia. 

More than 20 risk genes have been found so far and most of them only slightly increase a person’s risk of dementia. 

The most important risk gene for dementia is called apolipoprotein E (APOE). Certain versions (variants) of the APOE gene can make a person up to four times more likely to develop Alzheimer’s disease than people who don’t have this version of the gene. 

It’s important to remember that these higher-risk versions still don’t always cause dementia. Most people with higher-risk versions of the APOE gene don’t ever develop the condition. 

Diagnosing certain long-term health conditions earlier and managing them effectively may reduce their damaging effects on brain health as people get older. These include: 

• diabetes 
• hearing loss
• vision loss 
• head injuries 
• high blood pressure
• high cholesterol
• depression

Some long-term medical conditions may cause problems with a person’s thinking and memory that can develop into dementia in severe cases, such as multiple sclerosis, HIV or kidney disease. 

Down’s syndrome and other learning disabilities greatly increase a person’s risk of developing young-onset dementia, usually caused by Alzheimer’s disease.

There is a lot of evidence that our lifestyle choices can affect our risk of developing dementia. These behaviours and health conditions include: 

• physical activity 
• smoking 
• alcohol 
• social isolation 

Dementia risk is lowest in people who have healthy behaviours in mid-life (aged 40–65). Find out about how you can reduce your risk of developing dementia.

Overall, there are more women than men living with dementia. This is mostly because women tend to live longer than men.

The risk of getting dementia is about the same for men and women. However, women who are currently over 80 have a slightly higher risk of getting dementia than men their age.

The reasons why women over 80 have a higher risk of dementia than men over 80 are still unclear. It is possible that general differences in the lifestyles of these women and men over time have caused differences in their level of risk. For example, women currently in this age group may have had less access to education or work opportunities than men their age.

Menopause and dementia risk

There have also been concerns that levels of sex hormones around the time of menopause may affect a person’s risk of dementia. The evidence on this is still unclear. 

When a person goes through the menopause, their levels of oestrogen and progesterone fall. Some research has suggested that the earlier this happens in someone’s life, the higher their risk of dementia. However, clinical trials of hormone replacement therapy (HRT, which replaces these sex hormones) have not shown any effect on the risk of developing dementia. 

Until there is clearer evidence, HRT is not recommended as a way to help people reduce their risk of dementia. 

‘Cognitive reserve’ is when a person has disease in their brain but it takes longer for them to start showing symptoms. It is built up by keeping the brain active over a person’s lifetime.

The more cognitive reserve a person has, the longer it takes for any diseases in their brain to cause problems with everyday tasks. This means people with a larger cognitive reserve can delay getting dementia symptoms. People with a smaller cognitive reserve are at a higher risk of getting dementia in their lifetime.

The three most important factors that can lead to a smaller cognitive reserve are:

• leaving education early: a person who left school at an early age is more likely to have a smaller cognitive reserve than a person who stayed in full-time education for longer or who continued learning throughout their life 
• less job complexity: a person who has not used a range of mental skills during their lifetime of work – for example, memory, reasoning, problem-solving, communication and organisational skills – is more likely to have a smaller cognitive reserve 
• social isolation: a person who has not interacted much with other people during their life may also have a smaller cognitive reserve.

This means these factors are also risk factors for dementia.

While a lot of a person’s cognitive reserve is built up during their childhood and early adulthood, there are many things a person can do to increase their cognitive reserve later in life, such as staying mentally and socially active.

It’s still not clear if people from different ethnic groups in the UK have a higher chance of getting dementia. Some studies have found differences in certain locations but it’s hard to know if they reflect the situation in the UK population as a whole. 

A few studies have suggested that people from Black African, Black Caribbean and South Asian ethnic groups are more likely to get dementia than people from White ethnic groups. 

One possible reason for these differences is that people in these ethnic groups are more likely to develop diabetes and cardiovascular disease (CVD) as they get older – both diabetes and CVD are important risk factors for dementia. 

Differences in risk between different ethnic groups may be caused by other factors. For example, a recent study found that Black people in the UK may be more likely to have a common risk gene for dementia. Also, some ethnic groups may generally have had less access to education and work opportunities, and may be more likely to live in deprived areas. 

More evidence is needed to know if certain ethnic groups have a different level of dementia risk than others. 

A deprived area is an area with limited access to basic resources and services, such as suitable housing, education and work opportunities.

People who live in deprived areas are at a higher risk of getting dementia. This may be because the lack of opportunities in these areas makes it harder for a person to get further education and to access jobs that keep a person mentally active throughout their life.

More deprived areas also tend to have higher levels of air pollution and less access to health and social care. This makes it harder for a person to manage any health problems that can lead to dementia.

Air pollution

Certain forms of air pollution increase a person’s risk of dementia. These include very small particles from traffic fumes and from burning wood in the home, for example in a fireplace.