La démence à début précoce est liée à la santé et au mode de vie, ainsi qu'à la génétique

Risk factors for young-onset dementia

"Young-onset dementia has a very serious impact, because the people affected usually still have a job, children, and a busy life." - Dr Stevie Hendriks, researcher for the UK Biobank cohort study.

It’s thought that around 70,800 people in the UK and 200,000 in the US are living with young-onset démence^1,2. These people are all under the age of 65 and many are in their forties and fifties, although people have been diagnosed as young as 30.

Genetics - out of our control

Before this research, it was known that genetics play a big part in both dementia and young-onset dementia.

Specifically, carrying a gene called APOE4 makes a protein called apoliprotein E. Having two of these proteins has been linked to cell death in the brain, which in turn increases your chances of dementia.

According to study researcher Dr Hendriks, it's often assumed that genetics alone causes young-onset dementia: "But for many people we don't actually know exactly what the cause is. This is why we also wanted to investigate other risk factors in this study."

Socioeconomic status and education

Two factors relating to society and your environment were identified as reducing cognitive reserve, which describes your brain's capacity to think, problem-solve, and improvise as you age.

Having a lower cognitive reserve is directly linked to a higher risk of dementia symptoms at a younger age.

These factors also tend to be linked:

• Having a less formal education - it's thought that this may affect your familiarity with the items on the cognitive tests used to diagnose dementia.

• Having lower socioeconomic status - is often linked to having a lower-quality education.

Isolement social

Social isolation leads to la solitude, and this is a major and well-established risk factor for dementia in over 65s. In fact, in this age group it's estimated that social isolation increases your chances of dementia by 50%⁴.

Loneliness is more prevalent in the elderly community, but the UK Biobank cohort study reveals that being socially isolated can also lead to dementia in mid-life or possibly younger.

Exactly how this works unknown, but it's thought that social interactions use and exercise your brain in a way that helps to keep it healthy.

Associated health problems

Several factors identified in the study are health problems that appear to be linked with a higher chance of young-onset dementia.

The below were found to be the most significant, but lifestyle habits like fumer, problèmes de sommeil, and long-term niveaux de stress were also mentioned by researchers.

We may be in the early stages of understanding them and how these associations work, but for each health issue there is existing advice on the lifestyle changes you can make.

Problèmes d'audition

Experts think that perte auditive in later life may be the highest potentially modifiable risk factor for developing dementia, and it's now found to be significant for under 65s too. Hearing is an essential part of brain health and stimulation.

Possible lifestyle changes: The best way to protect your hearing is to avoid or limit exposure to very loud noise. If you already have some hearing loss, using hearing aids can reduce your chances of developing dementia⁵.

Getting your hearing checked regularly from age 40, as you may do for your sight, can help detect and manage hearing issues at an early stage. This is especially important if your working environment is noisy or may effect your hearing.

Carence en vitamine D

It's thought that vitamin D protects us against brain degeneration and viral infections. These infections may increase your risk of dementia, according to other studies⁶.

Possible lifestyle changes: The UK government recommends we all take vitamin D supplements between October and April, when it's difficult to obtain enough from sunlight.

High C-reactive protein (CRP) levels

Our liver produces more of a protein called C-reactive protein (CRP) when there is inflammation in the body. Inflammation causes cell damage that, according to the study findings, may be a factor in young-onset dementia.

Possible lifestyle changes: While short-term inflammation is a natural function of the body, long-term inflammation can be caused by certain unhealthy foods. Following an régime anti-inflammatoire may reduce associated health risks.

Hypotension orthostatique

Orthostatic hypotension is a form of low blood pressure that happens when standing after sitting or lying down. The relationship between this and young-onset dementia appears to be two-ways.

On the one hand, orthostatic hypotension can lead to brain damage that results in dementia, on the other, the researchers noted that it may also be an early symptom of Parkinson's dementia ou Lewy body dementia. They think that this can sometimes become an issue for someone years - or even decades - before they're diagnosed with young-onset dementia.

Possible lifestyle changes: Orthostatic hypotension can have different causes, and you'll need a doctor to help find the cause in order to treat the problem. For example, it could be due to dehydration, in which case you'll be be advised to drink more water.

AVC

The study found that people who had previously had a stroke were more likely to develop young-onset dementia. This is because having a stroke damages the brain.

Possible lifestyle changes: Current stroke prevention advice includes arrêter de fumer, following a healthy diet, having regular blood pressure and cholesterol checks, maintaining a healthy weight, being physically active, and drinking alcohol in moderation.

Maladies cardiaques

Having heart disease makes you more likely to have a stroke, which can cause brain damage and vascular dementia - when a lack of blood supply to the brain causes brain cells to die off.

Possible lifestyle changes: Not all types of heart disease are preventable, for example genetics can play a role. But some lifestyle habits can increase your risk of heart disease - such as being overweight, smoking, eating an unhealthy diet, not exercising enough, drinking too much alcohol, and taking other recreational drugs.

Diabète

It's known that type 2 diabetes, which can cause vascular brain injury, is associated with having a higher risk of dementia - a 60% increased risk according to some studies⁷. This latest research finds diabetes to be a significant factor for young-onset dementia as well.

Possible lifestyle changes: There's a wealth of information on preventing and managing type 2 diabetes, the main strategies involving healthy weight loss, diet, and exercise.

Alcohol use disorder

Alcohol use disorder (AUD) is the medical term for alcohol addiction, dependence and abuse. It's when you cannot stop or control your drinking despite the negative effects it's having on your health and life in general.

The study found that people diagnosed with AUD were more likely to develop young-onset dementia - specifically alcohol-related 'dementia'.

Experts have known that AUD can lead to dementia in over 65s for some time, because excessive and ongoing alcohol consumption can damage the brain, including the part responsible for your working memory⁸.

Possible lifestyle changes: Unlike other forms of dementia, with the right treatment, alcohol-related 'dementia' may be stopped or even improved. People with this condition will likely need several methods of support, including special prescription drugs, thiamine (vitamin B1) tablets, talking therapies⁸ and support services to help quit alcohol, such as We Are With You.

Reverse causation

Not every health problem associated with the disease in this study is a clear risk. Reverse causation means that a risk factor could be a symptom - and not the cause - of young-onset dementia.

Yet, they may appear to be risk factors because they become noticeable before the dementia becomes obvious and is diagnosed. These three factors fall into this category.

Dépression

This study highlighted that depression and young-onset dementia often go hand-in-hand, as it does with other forms of dementia.

According to Alzheimer's Society⁹, it's more likely that people develop depression as a result of the difficulties and worries of living with dementia, and it's often diagnosed when a person is in the early stages of the disease.

Experts also note that the diseases that can cause dementia can also sometimes cause depression.

No alcohol use

It may seem strange that not drinking alcohol was found to be linked with young-onset dementia, especially as alcohol use disorder is a risk factor.

However, the researchers noted that many people stop drinking after they develop memory loss. This is known as the 'healthy drinker effect'.

Weak hand grip strength

Having a lower hand grip strength isn't itself a condition, but it can be a sign that your muscles are wasting. This can be a symptom of dementia, but it could also be caused by disuse of the hands and fingers, or other conditions such as arthritis, peripheral neuropathy, or multiple sclerosis (MS).

Pour en savoir plus

1. Dementia UK: Young onset dementia: facts and figures.

2. Alzheimer's Los Angeles: Minorities and women are at greater risk for Alzheimer's disease.

3. Hendriks et al: Risk factors for young-onset dementia in the UK Biobank.

4. Centers for Disease Control and Prevention: Loneliness and social isolation linked to serious health conditions.

5. Alzheimer's Society: Hearing loss and the risk of dementia.

6. National Institute on Aging: Could a viral illness increase chances of developing Alzheimer’s or other neurodegenerative disease?

7. Gudala et al: Diabetes mellitus and risk of dementia: a meta‐analysis of prospective observational studies.

8. Alzheimer's Society: Alcohol-related 'dementia'.

9. Alzheimer's Society: Depression and dementia.