Dementia is a condition in which memory and other thinking problems prevent a person from independently performing activities of daily living. It can be caused by many different diseases affecting the brain. Alzheimer’s disease is the most common cause of dementia.

Alzheimer’s disease begins in the brain years before symptoms appear. Initial symptoms are mild and should not interfere with your normal daily life. It is not until later that the symptoms become severe enough to be called “dementia.”

Other common causes of dementia include vascular disease that blocks blood flow to the brain and Lewy body disease.

Like Alzheimer’s disease, these diseases develop in the brain over many years. They eventually lead to vascular dementia and Lewy body dementia.

What is dementia?

Dementia is a group of symptoms. It is caused by a variety of diseases that damage the brain. Symptoms worsen over time and may include:

  • Memory loss
  • Confusion and needing help with daily tasks
  • Language and comprehension issues
  • Change in behaviour.

Dementia is progressive, and although symptoms may be relatively mild in the beginning, they become worse over time.

Types of dementia

Alzheimer’s disease is the most common cause of dementia, but there are many other possible causes.

Vascular dementia

Vascular dementia is caused by blockage of blood flow to the brain and is often linked to stroke and plaque build-up in the arteries. Symptoms vary and may appear gradually or suddenly.

Lewy body dementia

Lewy body dementia is a progressive disease caused by protein deposits in the nerves that interfere with electrical signals. This can cause symptoms such as changes in thinking, confusion, and changes in activity patterns.

Parkinson’s disease, dementia

Parkinson’s disease dementia is a cognitive decline that occurs in many people with Parkinson’s disease more than a year after diagnosis. It is estimated that 50–80% of people with Parkinson’s disease will eventually develop dementia, with the average time to onset being about 10 years.

Frontotemporal dementia

Frontotemporal dementia is a group of symptoms characterized by loss of brain function in the part of the brain behind the forehead or ears. According to the Alzheimer’s Association, changes in behavior are often the first symptom of frontotemporal dementia.

Posterior cortical atrophy

Posterior cortical atrophy is the progressive destruction of the outer layer of the brain, called the cortex, which is located at the back of the brain. Symptoms vary, but often include problems performing visual tasks such as reading or recognizing moving objects.

Creutzfeldt-Jakob disease

Creutzfeldt-Jakob disease is a rare infectious disease that affects about 350 people in the United States each year. It causes dementia, which progresses rapidly and often begins with muscle coordination problems, personality changes, and vision problems. About 70% of people die within a year.

Wernicke-Korsakoff syndrome

Wernicke-Korsakoff syndrome is a brain disease caused by vitamin B1 deficiency. The most common cause is chronic alcohol abuse. Symptoms include double vision, confusion, drooping of the upper eyelid, and loss of muscle coordination.

Mixed dementia

Mixed dementia occurs when a person has more than one type of dementia. The most common combination is vascular dementia and Alzheimer’s disease. This combination affects 22% of older adults.

Normal pressure hydrocephalus

Normal pressure hydrocephalus is a condition caused by a buildup of fluid within the ventricles of the brain. This can cause problems with sensation, movement, and bladder control. In most cases, the cause is unknown. However, head trauma, infection, brain hemorrhage, and surgery can all contribute to the development of the disease.

Huntington’s disease

Huntington’s disease is a rare disease that causes the destruction of nerve cells in the brain. This occurs due to genetic abnormality. Early symptoms may include mood changes, psychosis, and decreased coordination.

What is Alzheimer’s disease?

Alzheimer’s disease is the most common cause of dementia. Nearly two in three people with dementia in the UK have Alzheimer’s disease (also known as ‘Alzheimer’s disease’).

Alzheimer’s disease is a physical disease that affects the human brain. This begins years before symptoms appear.

The early symptoms of Alzheimer’s disease are mild and do not affect a person’s ability to perform daily activities independently. This is called mild cognitive impairment (MCI).

At this stage, it is often impossible to say with certainty that a person’s symptoms are caused by Alzheimer’s disease, as there are many other possible causes.

Eventually, Alzheimer’s disease causes severe damage to the brain and dementia develops. Technically this type of dementia is called Alzheimer’s dementia. However, most people, including medical professionals, simply refer to it as “Alzheimer’s disease”.

For most people, Alzheimer’s disease begins in and around the parts of the brain that control memory. However, some rare types of dementia cause a different set of symptoms because the disease begins in a different part of the brain. This is called “atypical Alzheimer’s disease.” For example, posterior cortical atrophy occurs in the back part of the brain in Alzheimer’s disease and often causes visual loss.

Causes of alzheimer’s disease

The causes of Alzheimer’s disease are complex, but one of the main causes is the buildup of two substances called amyloid and tau in the brain. When conditions in the brain are abnormal, they clump together to form small structures called plaques and neuronal changes. This makes it difficult for the brain to function properly.

Over time, this disease causes body parts to become smaller. It also reduces the amount of important chemicals needed to send messages to the brain.

There is currently no cure for Alzheimer’s disease. However, for some people, treatment may temporarily relieve symptoms or slow progression.

What are the other main types of dementia and what are their causes?

Vascular dementia: This is the second most common type of dementia. It is caused by problems with the blood supply to areas of the brain.

Lewy body dementia: Lewy bodies are small clumps of protein that accumulate in the brain. When this happens it becomes Lewy body disease. There are two main types:

Dementia with Lewy bodies: When the first symptoms of dementia with Lewy bodies are those of dementia, it is known as dementia with Lewy bodies (DLB).

Dementia in Parkinson’s disease: Lewy body disease can also lead to Parkinson’s disease, which primarily involves movement disorders but can also lead to dementia after a few years. In such a situation, it is known as Parkinson’s disease dementia.

Frontotemporal dementia: This is a less common type of dementia. It can be caused by many different types of diseases, but they all primarily affect the front or sides of the brain, known as the frontal and temporal lobes.

Mixed dementia. Mixed dementia is usually diagnosed when clinical symptoms of two or more different types of dementia are combined, for example, when a person has symptoms of both Alzheimer’s disease and Lewy body dementia.

How do I know what type of dementia I have?

Dementia should be diagnosed by a health professional who is an expert in dementia, usually after a detailed assessment by a local memory service.

If someone is diagnosed with dementia, ideally their doctor should tell them what type of dementia they have. However, this is not always the case. Determining the cause of dementia can be difficult, especially in the early stages.

Although it is not always important to know the cause of dementia right away, it can help better understand a person’s symptoms and guide appropriate treatment.

Does the Alzheimer’s Society support people with dementia and Alzheimer’s disease?

We support people living with dementia. We support people with mild cognitive impairment and those who are concerned about their memory. Find out how the Alzheimer’s Society can help you.

We are a vital source of support, we provide support to all who need it now and we look forward to the future for all.

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