Diseases that cause dementia

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Dementia is a group of symptoms. Alzheimers disease is one possible cause
A common confusion

There are many diseases that can cause dementia symptoms. These are the causes of dementia. They are also called the types of dementia, or simply dementias. A person with dementia could have one or more diseases that cause dementia. The most common dementia-causing disease is Alzheimer’s Disease. Others include vascular dementia, Fronto-Temporal Dementia (FTD), Dementia with Lewy Bodies, and mixed dementia. There are said to be around a hundred causes of dementia.

Unfortunately, articles on dementia do not always explain that the dementia symptoms can be caused by many diseases. The word “dementia” is often used in place of the name of the disease causing it. Many articles use “dementia” and “Alzheimer’s” interchangeably; this confuses readers about the relationship between dementia and Alzheimer’s.

Sections on this page:

Some basic information on dementia and diseases that cause it.

  • Dementia symptoms can be caused by one or more medical conditions.
  • Dementia is the name of a group of symptoms. A person may have some of these symptoms and not the others. The doctor checks the person and decides whether to diagnose the person with dementia.
  • Some medical causes of dementia can be treated. In these cases, medicines reverse the symptoms. The person can become normal. This is called reversible dementia.
  • In many dementia-causing diseases, the damage done to the brain by the disease cannot be reversed. Such dementia is called “irreversible dementia”.
  • In most irreversible dementias, the brain keeps getting more damaged over time. This is called progressive dementia. The person with dementia finally becomes fully dependent and bed-ridden. There is no cure.
  • In some irreversible dementias, the brain damage stays at the same level. This is called a plateau. Or the damage gets worse in steps. It stays at the same level for some time, then gets worse over a short period of time, and stays at this new level for some time. This is called step-wise progression of dementia.
  • Medicines available for irreversible dementias try to reduce the symptoms. They cannot change the underlying disease. They cannot repair the damage already done. The symptom relief may improve the person’s quality of life, especially in early stages, for some patients. But medicines do not slow down the progress of the disease. There are no “disease-modifying” medicines approved for use in India so far. Researchers are trying to find better medicines.
  • Dementia symptoms get worse when the brain gets more damaged because the disease has progressed. Existing symptoms get worse. More symptoms may also appear. Which symptoms are seen, and how they get worse, depends on which disease is causing dementia.
  • Family members of persons with dementia often worry that they will get dementia. Their risk of dementia depends on many factors. Family members can ask the doctor and stay informed about research in this area.

Note that most material on dementia care assumes that the person has an irreversible dementia. It is assumed that all reversible causes have been diagnosed and cured. All care advice is given assuming that existing symptoms are being caused by an irreversible dementia disease.

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Reversible causes of dementia.

There are several reversible causes of dementia. Here the disease causing the symptoms can be treated. Treatment will reverse the dementia symptoms.

One common reversible cause of dementia is depression. Such dementia is called depressive pseudodementia or depressive dementia. Another common cause is medications. Here, symptoms are seen because of a reaction to some medicine. They could be a side-effect of some medicine. Or they happen due to a toxic buildup in the body. Some medicines affect the brain’s neurotransmitters and cause dementia symptoms.

Well-known reversible causes include hypothyroidism, infections, and vitamin B12 deficiency. Electrolyte imbalance, a common problem in elders, may also be confused with dementia. Dehydration and poor nutrition are other possible causes. Ups and downs in blood sugar may be confused with dementia. A person with hearing loss or poor vision may not respond well to others. This may be mistaken as dementia.

Some causes are less common. One is normal pressure hydrocephalus (NPH). Here excess fluid is built up in the brain. A person with NPH may get relief if a shunt can remove this excess fluid. If there is chronic subdural haemotoma, surgical evacuation can be considered. Also, some uncommon causes may seem unrelated to the brain. For example, some studies show that celiac disease can cause dementia-like symptoms. Diseases with symptoms similar to neurodegenerative diseases may also get mistaken for dementia. One example is Lyme’s disease.

A medical checkup is needed to know which disease is causing the dementia symptoms. Doctors have to look at the medical history and current medicines. Investigations are done. Based on these the doctor will determine if the person has dementia and will try to find out which disease is causing the symptoms. A person showing the symptoms may have more than one dementia-causing disease.

If you have dementia like symptoms, or are worried about someone who has symptoms, please do not assume it is dementia without getting a proper diagnosis. Contact doctors and get a check up done. Remember that a person can have more than one medical problem that can cause dementia symptoms. Also remember that someone with dementia can also develop other diseases which can worsen the dementia symptoms. So you must remain alert about all medical problems. Get checkups done regularly to detect any new problems.

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Irreversible causes of dementia.

Most dementia cases are irreversible. The disease causing the symptoms cannot be cured. In some such cases the person’s symptoms stay at the same level for a long time. This may happen for someone who has vascular dementia. But most irreversible dementias are “progressive”. The symptoms get worse with time. The person’s abilities keep declining till the person is fully dependent.

Alzheimer’s Disease is the most common cause of dementia. It is an irreversible and progressive disease. According to the Dementia India Report 2010: The common causes accounting for 90% of all cases are Alzheimer’s disease, Vascular dementia, Dementia with Lewy bodies and Frontotemporal Dementia.

The Dementia India Report 2010 gives the proportion of common subtypes of irreversible dementia as below. See below data from Table 1 of the report.

Dementia subtypeEarly characteristic of dementiaProportion of dementia cases
Alzheimer’s Disease (AD).Impaired memory, apathy and depression, gradual onset.50-75%
Vascular Dementia.Similar to AD but memory less affected and mood fluctuations more prominent. Physical frailty. Stepwise progression.20-30%
Dementia with Lewy Bodies.Marked fluctuation in cognitive ability. Visual hallucinations. Parkinsonism (tremor and rigidity).<5%
Frontotemporal dementia.Personality changes. Mood changes. Disinhibition. Language difficulties.5-10%

A person may also have “mixed” dementia where the dementia is a result of Alzheimer’s Disease along with some other disease.

Let’s look at some types of dementia and their typical symptoms. Take Alzheimer’s Disease (AD). The probability of AD increases with age. The disease often starts at an older age. In most cases, in the beginning the person faces memory problems or has problems learning new things or making decisions. Problems in speech and other problems appear later. But Fronto-Temporal Dementias (FTD) may start at a younger age. Initial symptoms are usually language difficulties, mood changes, personality changes, and inappropriate social behavior. Persons with FTD may make rude or sexual comments. They may not care about people around them, show poor judgment and make unwise financial decisions. Some start overeating. They may not have memory loss, a symptom typical in early Alzheimer’s.

One common cause of dementia in India is vascular dementia, which occurs because blood flow to the brain is reduced or blocked. This means the brain cells do not get enough oxygen and nutrients. This may happen because of a series of strokes. This is also called vascular cognitive impairment (VCI) or multi-infarct dementia. Symptoms depend on which parts of the brain were damaged because of vascular problems. Vascular dementia can exist along with Alzheimer’s Disease. This is called mixed dementia. It has its own typical symptoms.

Dementia symptoms get worse when the underlying disease progresses. In Alzheimer’s Disease, this could be gradual or rapid. It could range from a few years to even a couple of decades. However, in vascular dementia, symptoms may remain at the same level if the person gets no more strokes. When the person suffers more strokes, there is a rapid decline because another part of the brain has also been damaged.

Most caregiving material is written for Alzheimer’s Disease, or for dementia in general. This material can be helpful even for non-Alzheimer’s dementia because many problems are similar. But some aspects of care may be different because they depend on the disease. Caregivers should get information from the appropriate communities to learn how the particular disease will affect someone.

Caregivers must make sure that all the person’s doctors, not just the specialists, know the diagnosis. They must ask about medicine side-effects. Some medicines help in one form of dementia but not in other forms of dementia. They may even cause harm. For example, some drugs help in hallucinations in AD patients but can harm LBD patients. Unfortunately, LBD is often mistaken for AD. Support forums for specific diseases can help caregivers learn about such problems.

On a related note, many persons who have Parkinson’s Disease will also develop dementia (called Parkinsonian dementia, and part of the overall “Lewy Body Dementia” umbrella ). The nature of correlation between Parkinson’s Disease and dementia is a matter of active research. As laypersons concerned about our loved ones, however, what is important to remember is that persons with Parkinson’s Disease also have some cognitive problems. Many persons with Parkinson’s Disease will go on to develop dementia at later stages.

Additionally, it is now being discussed that some pathologies associated with dementia are more common in the oldest old such as hippocampal sclerosis of aging (HS) and Limbic predominant Age-related TDP-43 Encephalopathy (LATE) , but work is still on to understand these better and they are not used during diagnosis.

While very rare, there are also some genetic conditions that cause dementia. These include autosomal dominant and autosomal recessive diseases, and genetic abnormalities. For example, there are around 70 rare neurodegenerative diseases (such as Batten disease) that can cause childhood dementia. Also there are conditions like Down syndrome (trisomy 21) where, persons who live long enough are almost certain to develop Alzheimer’s. Another rare, genetic cause of dementia is Huntington Disease. There are also rare, genetically caused “familial” (inheritable) forms of some dementia diseases which have young-onset.

Update in March 2023: The 2023 report on dementia from the Alzheimer’s Association, USA, includes some (USA) estimates of the common causes of dementia. It also mentions that community studies show mixed dementia as considerably higher, and most common in people aged 85 or older. It mentions that a systematic review found that 3.6% of dementia cases were due to Parkinson’s Disease (PD) and 24.5% of people with PD developed dementia. It also mentions Hippocampal Sclerosis (HS) as being present in about 3% to 13% of the cases, often with other causes of dementia. An estimated 0.4% to 2% of dementia cases are due to HS alone, and it is a common cause of dementia in persons 85 and older, but often misdiagnosed as Alzheimer’s.

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See Also (References for detailed reading).

Resources/ references from Dementia Care Notes and related sites.

To understand the relation between dementia and Alzheimer’s, see videos in English and Hindi for: What is the Difference between Dementia and Alzheimer’s? (English one also in player below):

External Resources/ references.

Data from India on dementia, causes, status of care, and current and estimated prevalence: The Dementia India Report 2010 (PDF file)Opens in new window(archived copy) .

The 2023 Alzheimer’s Facts and Figures report (Alzheimer’s Association, USA, is at this link Opens in new window .

Below there are many links to sites containing information on various causes of dementia. You may also be looking for information on these by searching the Internet, reading books and manuals, talking to experts, etc. Note that the names and groups of various dementia-causing diseases are modified very often. They are not standard across websites, documents and books. Some terms earlier used for a single disease are now “umbrella terms” that include many related dementias. As an example, consider FTD. Some sites call FTD frontotemporal degeneration, some call it frontotemporal dementia or frontotemporal disorders, and some sites use the term “Pick’s Disease.” Terminology can confuse and mislead. Please be alert about these different terms. Ask your doctor if you get confused.

Links to understand more about various diseases that cause dementia symptoms (reversible and irreversible):

Important sites to learn about specific diseases that cause dementia.

Sites for Alzheimer’s Disease (AD): USA’s Alzheimer’s Association Opens in new window and the International body, Alzheimer’s Disease International Opens in new window.

Sites for Fronto-Temporal Dementia (FTD). The Association for Frontotemporal Degeneration Opens in new window. Alzheimer’s Association, USA has an FTD page at alz.org Opens in new window. National Institute on Aging has a page on Frontotemporal Disorders: Information for Patients, Families, and Caregivers (ADEAR) Opens in new window.

Sites for Lewy Body Dementia. Lewy Body Society Opens in new window, Alzheimer’s Association, USA has a Lewy Body Dementia page at alz.org Opens in new window, National Institute on Aging has a page on Lewy Body Dementia: Information for Patients, Families, and Professionals (ADEAR) Opens in new window, and there is also a Lewy Body Dementia Association, Inc. Opens in new window. Special reading on the common misdiagnosis of LBD as AD is available at a Page from LBDA on treatment options Opens in new window. Page explaining misdiagnosis is available at Lewy Body Dementia: The Under-Recognized but Common Foe Opens in new window.

Sites for Parkinson’s Disease (note that many Parkinson’s Disease patients also develop dementia). From UK Parkinson’s UK Opens in new window who also have an explanation of Parkinson’s and Dementia Opens in new window. The European organization is at European Parkinson’s Disease Association Opens in new window,. Alzheimer’s Association, USA has a Parkinson’s Disease page at alz.org Opens in new window and the national Institute of Health has a page on Parkinson’s Opens in new window. A collection of sites can be also seen on this page: Parkinson’s Disease Organisations Opens in new window. An Indian site is the Parkinson’s Society of IndiaOpens in new window.

Sites for vascular dementia. Mayo Clinic has explanation of vascular dementiaOpens in new window, or see NINDS pages on multi-infarct dementia Opens in new window, or the Alzheimer’s Association USA’s explanation at their Vascular dementia page at alz.org Opens in new window.

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Dementia Care Notes