Key takeaways

  • Dementia isn’t one specific disease, but rather a term for brain changes that lead to memory loss and difficulty with daily tasks, with Alzheimer’s being the most prevalent type.
  • Besides Alzheimer’s, other forms of dementia include vascular dementia (caused by reduced blood flow to the brain), Lewy body dementia, frontotemporal dementia, and several rarer conditions.
  • While most dementias are irreversible, early diagnosis and treatment can often help manage symptoms or slow the progression of the disease, highlighting the importance of consulting a professional if you notice potential signs.

Doctors use the term “dementia” to describe severe changes in the brain that cause memory loss. These changes also make it difficult for people to perform basic daily activities. In most people, dementia causes changes in behavior and personality.

All types of dementia affect areas of the brain that control:

  • language
  • memory
  • decision making

Most cases of dementia are due to disease and are irreversible. Rare exceptions do occur, causing dementia because of depression or drug and alcohol misuse.

Different types of dementia progress differently. Most are graded along a set of similar stages. In the article, we examine some common causes as well as some rare and notable ones.

Alzheimer’s disease is the most common type of dementia among older adults in the United States, accounting for about 60% to 80% of all dementia cases.

  • forgetting names and recent events
  • neglecting personal care
  • mood and personality changes
  • disorientation

Though depression can be an early indicator of Alzheimer’s disease, it’s not part of the disease itself. People may need treatment for depression as a separate disorder. Doctors occasionally misdiagnose depressed older adults as having Alzheimer’s disease or another type of dementia.

Alzheimer’s disease involves brain cell death. People are more likely to experience confusion and mood changes as the disease progresses. They also have difficulty speaking and walking.

Older adults are more likely to develop Alzheimer’s. About 5% to 6% of cases of Alzheimer’s are early onset Alzheimer’s, occurring in people in their 40s or 50s.

Experts break down the progression of Alzheimer’s into seven stages, with recognizable dementia starting around Stage 4. Impairment worsens gradually until Stage 7. At this point, most people with Alzheimer’s are likely to face severe challenges in speech and movement.

Risk factors for Alzheimer’s disease

Alzheimer’s disease has many different causes that often work together, none of which are fully understood. Known risk factors for Alzheimer’s disease include:

The second most common type of dementia is vascular dementia. A lack of blood flow to the brain causes it. Vascular dementia can occur as you age. This can be related to atherosclerotic disease, diabetes, high blood pressure, and more. Strokes are the most common cause of vascular dementia.

Depending on the cause, symptoms of vascular dementia can appear slowly or suddenly. Confusion and disorientation are common early signs. Later, people find it hard to complete tasks or concentrate for long periods. Vascular dementia can cause vision problems and sometimes hallucinations.

Discrete events may often cause vascular dementia. It tends to appear and worsen in a stepwise fashion than the progressive decline that happens in Alzheimer’s disease.

Risk factors for vascular dementia

Risk factors for vascular dementia are numerous and include:

While the exact cause of dementia with Lewy bodies is unknown, it involves abnormal protein deposits in nerve cells throughout the brain. These deposits interrupt chemical messages in both the central and autonomic nervous systems, causing a range of symptoms including memory loss and disorientation.

People may also refer to DLB as Lewy body dementia (LBD), but DLB is just one type of LBD. Parkinson’s disease dementia (discussed below) is the other type.

People with DLB may also:

  • experience visual hallucinations
  • have difficulty falling asleep at night
  • fall asleep unexpectedly during the day
  • faint or become lost or disoriented

DLB shares many symptoms with Parkinson’s and Alzheimer’s diseases. For example, many people develop trembling in their hands, have difficulty walking, and feel weak. Lewy bodies can be present in the brains of those with Alzheimer’s and often in those with Parkinson’s as well.

Risk factors for Lewy body dementia

Known risk factors for both types of LBD include:

  • male gender
  • changes in posture
  • instability with walking
  • greater difficulty with movement
  • symptoms on the left and right sides of the body
  • experience hallucinations earlier
  • no response to medication

According to the Parkinson’s Foundation, up to 70% of people with Parkinson’s disease eventually develop dementia, though recent studies suggest that the percentage may be lower.

Early signs of this type of dementia are problems with reasoning and judgment. For example, a person with Parkinson’s disease dementia (PDD) might have difficulty understanding visual information or remembering how to do simple daily tasks. They may even have confusing or frightening hallucinations.

PDD can also cause a person to be irritable. Many people become depressed or paranoid as the disease progresses. Others have problems with speech, might forget words, or get lost during a conversation.

One unique risk factor for PDD is a set of motor difficulties known as postural instability and gait disturbance. This includes difficulty initiating movement, shuffling, and problems with balancing and falling.

Parkinson’s disease dementia vs. dementia with Lewy bodies

Both PDD and DLB involve Lewy bodies, and both come under the category of “Lewy body dementia.”

When motor symptoms are the first to appear, followed by dementia, doctors typically diagnose PDD.

When cognitive symptoms are the first to appear, doctors typically diagnose DLB.

Frontotemporal dementia (FTD) involves several types of dementia that affect only the front and side parts of the brain. These areas control language and behavior. FTD is sometimes referred to as Pick’s disease, though that is just one form of FTD.

FTD typically affects people ages 45 to 65 years. Scientists don’t know what causes FTD. However, they know it runs in families. They have identified specific gene mutations in people with the disease.

FTD can cause loss of inhibitions and motivation and can cause compulsive behavior. It also causes people to have problems with speech, including forgetting the meaning of common words. FTD can have more severe effects on speech than Alzheimer’s.

Unlike Alzheimer’s, memory problems associated with FTD tend to occur later in disease progression.

FTD is the most common form of dementia that occurs in people with amyotrophic lateral sclerosis (ALS).

Mixed dementia is a situation in which a person has more than one type of dementia. Mixed dementia is very common, and the most common combination is vascular dementia and Alzheimer’s. One 2017 research review suggests that 22% of older adults had both conditions, though more recent studies note it could be higher.

Mixed dementia can cause different symptoms in different people. Some people experience memory loss and disorientation first, while others have behavior and mood changes. Most people with mixed dementia have difficulty speaking and walking as the disease progresses.

Normal pressure hydrocephalus (NPH) is a condition that causes a person to build up excess fluid in the brain’s ventricles. NPH accounts for as much as 6% of all dementias.

The ventricles are fluid-filled spaces designed to cushion the brain and spinal cord. They rely on the right amount of fluid to work properly. When the fluid builds up excessively, it places extra pressure on the brain. This can cause damage that leads to dementia symptoms.

Diagnosis of NPH can take time and often requires many tests to rule out other forms of dementia. The Alzheimer’s Association estimates that less than 20% of people with NPH receive a proper diagnosis.

Seeking treatment as early as possible can help a doctor intervene before additional brain damage occurs. Doctors may be able to cure NPH with surgery.

Risk factors of normal pressure hydrocephalus

Some of the potential causes of NPH include:

  • injury
  • bleeding
  • infection
  • brain tumor
  • previous brain surgeries

Creutzfeldt-Jakob disease (CJD) is one of the rarest forms of dementia, affecting 1 in 1 million people worldwide each year. CJD progresses very quickly, and people often die within a year of diagnosis.

Symptoms of CJD are similar to other forms of dementia. Some people experience agitation, while others experience depression. Confusion and loss of memory are also common. CJD affects the body as well and causes twitching and muscle stiffness.

CJD occurs when prions, or unusual and misfolded proteins, appear in the body and trigger the development of additional prions in the brain, leading to brain cell death.

Types of Creutzfeldt-Jakob disease

Experts don’t fully understand prions and the diseases they cause, but they generally break down CJD cases into the following three categories:

  • Sporadic Creutzfeldt-Jakob disease: This is the most common type, in which the origin of prion spread remains a mystery.
  • Familial Creutzfeldt-Jakob disease: Inherited genetic changes cause this type and can cause the production of the prion protein.
  • Acquired Creutzfeldt-Jakob disease: Though now exceedingly rare, exposure to abnormal prion protein can cause variants of CJD, primarily due to ingestion of infected meat.

Wernicke-Korsakoff syndrome (WKS) is a combination of two disorders: Wernicke disease and Korsakoff syndrome.

People usually get Wernicke disease (aka Wernicke encephalopathy) due to a lack of vitamin B1, leading to bleeding in the lower sections of the brain. Wernicke disease can cause physical symptoms like double vision and a loss of muscle coordination.

At a certain point, the physical symptoms of untreated Wernicke’s disease tend to decrease, and the signs of Korsakoff syndrome start to appear. Advanced Wernicke’s disease causes Korsakoff syndrome, which is a memory disorder. People with Korsakoff syndrome may have difficulty:

  • processing information
  • learning new skills
  • remembering things

Sometimes, people with WKS make up information to fill in the gaps in their memory without realizing it.

WKS can be a result of malnutrition or chronic infections. However, the most common cause is alcohol use disorder.

Though the symptoms resemble those of most other dementias, WKS is unique in that it is preventable and, when addressed early, curable.

Huntington’s disease is a genetic condition that causes dementia. In adults, it typically first causes symptoms when a person is in their 30s or 40s. The condition causes a premature breakdown of the brain’s nerve cells, which can lead to dementia as well as impaired movement.

Symptoms associated with Huntington’s disease include impaired movements, such as jerking, difficulty walking, and difficulty swallowing. The symptoms of dementia in Huntington’s disease are similar to most other forms of dementia, with mood changes, anger, and depression particularly common.

More than 100 different diseases may cause dementia. Alzheimer’s disease is the most common cause, accounting for a majority of cases.

Since dementia can develop in multiple ways, it’s also possible for someone to develop multiple types of dementia. This is known as mixed dementia, which is also very common.

Although dementias usually aren’t curable or reversible, treatments are often available to help slow progression or manage symptoms. Consult a healthcare professional if you notice signs of dementia in yourself or a loved one and want to learn more.