Ageing, lifestyle factors, genetics, and health conditions can all contribute to dementia.

Dementia is an umbrella term for a collection of symptoms that include memory loss and cognitive changes. Brain damage or various diseases can cause abnormal brain changes, which can cause dementia.

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There are different types of dementia that can result from various causes. The different types of dementia link to certain forms of brain damage in specific areas of the brain.

Most types of dementia occur due to proteins accumulating in the brain. In Alzheimer’s disease, abnormal protein deposits called amyloid plaques and tangles form and damage nerve cells.

Parkinson’s disease, dementia, and Lewy body dementia occur due to abnormal protein deposits called Lewy bodies.

Vascular dementia occurs due to reduced blood flow to the brain, such as through a stroke, which damages brain cells. Certain infections, such as HIV, and high consumption of alcohol may contribute to the development of dementia.

It is not common to inherit dementia, but some rare types of dementia can be genetic. Traumatic brain injury may damage the brain and increase the risk of developing dementia.

Researchers are still not clear on what causes Alzheimer’s disease, but it is likely due to a combination of factors, which include:

  • Age-related changes in the brain: Changes in the brain, such as inflammation and blood vessel damage, may occur with age and damage brain cells.
  • Genetics: Inheriting certain genetic variants may increase the risk or cause Alzheimer’s disease.
  • Overall health: Certain health conditions may link to the development of Alzheimer’s disease, including high blood pressure, diabetes, obesity, and depression.
  • Lifestyle: Certain lifestyle factors may increase the risk of Alzheimer’s disease, such as smoking and physical inactivity.

Many brain changes occur in the development of Alzheimer’s disease. A key feature of Alzheimer’s disease is the formation of amyloid plaques and tau tangles, which disrupt communication between nerve cells in the brain.

Damage to blood vessels in the brain can cause vascular dementia. This damage disrupts the flow of oxygen and blood to the brain, leading to abnormal brain changes.

People with vascular dementia usually show brain abnormalities, including:

  • evidence of previous strokes
  • thickening of blood vessel walls
  • changes in white matter, which is brain tissue containing nerve fibers and helps different regions of the brain communicate

Conditions that cause blood vessel damage can increase the risk of vascular dementia, such as:

Researchers have not found the exact cause of Lewy body dementia. In most people with Lewy body dementia, there is no family history of the condition. So far, there is no definitive research linking any genes to Lewy body dementia.

Lewy body dementia occurs due to a buildup of abnormal protein deposits called Lewy bodies. This buildup contributes to the loss of nerve cells in the brain that produce neurotransmitters.

Neurotransmitters are chemical messengers that allow nerve cells to communicate. Neurotransmitters such as acetylcholine and dopamine are important for cognitive abilities, learning, memory, and movement.

The following factors may increase the risk of Lewy body dementia:

In around a third of all frontotemporal dementia (FTD) cases, people inherit it. The only known risk factors for FTD are a family history of the condition or a similar disorder.

There are many different genes that can cause FTD, and each gene has its own inheritance pattern.

Most people with FTD do not inherit the condition directly, but in some cases, it can pass directly from a parent to a child. In around 40% of cases, people with FTD have at least one close relative who has a type of dementia.

Rare causes of dementia include:

  • Atypical Alzheimer’s disease: The same type of brain changes that occur with Alzheimer’s disease cause atypical Alzheimer’s disease, but the changes begin in a different region of the brain and cause different symptoms.
  • Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL): Inheriting a faulty gene causes CADASIL.
  • Creutzfeldt–Jakob disease (CJD): A malformed protein in the brain, called a prion, causes CJD. People may inherit CJD or acquire it. In most cases, there is no known cause of CJD.
  • Huntington’s disease: Huntington’s disease is a genetic, inherited condition.
  • HIV-associated neurocognitive disorder (HAND): People with HIV may develop cognitive impairment.
  • Progressive supranuclear palsy (PSP): The exact cause of PSP is unknown.
  • Normal pressure hydrocephalus (NPH): NPH can occur due to factors such as brain injury, infection, or hemorrhage, or may have no known cause.
  • Corticobasal syndrome (CBS): There is no known cause of CBS, but it may link to tau protein accumulating in the brain.

Risk factors for dementia include:

  • older age
  • smoking
  • high blood pressure
  • obesity
  • diabetes
  • physical inactivity
  • unhealthy diet
  • excessive alcohol
  • depression
  • hearing loss
  • traumatic brain injury
  • social isolation
  • genetics

Genetics, age, and certain health conditions can increase the risk of mild cognitive impairment (MCI). MCI increases the risk of developing dementia.

If people have concerns that they or someone else may have dementia, it is important to contact a doctor. Symptoms may include changes in behavior, mood, communication, and memory.

Other conditions may cause similar symptoms, but it is important to find the underlying cause and start any necessary treatment.

Various factors can cause changes in the brain that can lead to dementia. These can include ageing, health conditions, genetics, and lifestyle factors.

If people think they might have dementia, it is important to contact a doctor to find out the cause of symptoms.