Dementia is a term used 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 affects three areas of the brain:

  • language
  • memory
  • decision-making

Most cases of dementia are caused by a disease and can’t be reversed. Rare exceptions do occur, generally in cases of dementia caused by depression or drug and alcohol abuse.

Different types of dementia follow different pattens of progression, though most are graded along a set of similar stages.

Alzheimer’s disease is the most common type of dementia. Between 60 and 80 percent of cases of dementia are caused by this disease, according to the Alzheimer’s Association. Early signs of Alzheimer’s disease include forgetting names and recent events, neglecting personal care, mood and personality changes, disorientation, and more. Though depression can be an early indicator of Alzheimer’s disease, it is not part of the disease itself, and must be treated separately as a disorder. Occasionally, depressed older adults are misdiagnosed as having Alzheimer’s disease.

Alzheimer’s disease is characterized by brain cell death. As the disease progresses, people are more likely to experience confusion and mood changes. They also have trouble speaking and walking.

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


The progression of Alzheimer’s is broken down into seven stages. Symptoms generally appear at Stage 2, though recognizable dementia begins around Stage 4. Impairment worsens gradually until Stage 7, at which point most people with Alzheimer’s are likely to face severe challenges in speech and movement.

As with most types of dementia, the level of care required varies greatly along with the progression of symptoms.

Risk factors

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

  • Age
  • Family history
  • Genetics

The second most common type of dementia is vascular dementia. It’s caused by a lack of blood flow to the brain. Vascular dementia can happen as you age and can be related to atherosclerotic disease, diabetes, high blood pressure, and more. Strokes are the most common cause of vascular dementia.

Symptoms of vascular dementia can appear slowly or suddenly, depending on their cause. Confusion and disorientation are common early signs. Later on, people also have trouble completing tasks or concentrating for long periods of time. Vascular dementia can cause vision problems and sometimes hallucinations as well.

Because it is often caused by discrete events, vascular dementia tends to appear and worsen in more of a stepwise fashion than the progressive decline caused by Alzheimer’s disease.

Risk factors

Risk factors for vascular dementia are numerous and include:

Dementia with Lewy bodies, also known as Lewy body dementia, is caused by protein deposits in nerve cells. This interrupts chemical messages in the brain and causes memory loss and disorientation.

People with this type of dementia also experience visual hallucinations and have trouble falling asleep at night or fall asleep unexpectedly during the day. They also might faint or become lost or disoriented.

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

For those with Parkinson’s, known risk factors for also developing Lewy body dementia are:

  • male gender
  • changes in posture
  • instability with walking
  • greater difficulty with movement
  • symptoms seen on the left and right sides of the body
  • experiencing hallucinations earlier
  • symptoms not responding to medication

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

This type of dementia can also cause a person to be irritable. Many people become depressed or paranoid as the disease progresses. Others have trouble speaking and might forget words or get lost during a conversation.

One unique risk factor for dementia in people with Parkinson’s disease is a set of motor difficulties known as postural instability and gait disturbance (PIGD), which include difficulty initiating movement, shuffling, and problems with balancing and falling.

Like Lewy body dementia, dementia in Parkinson’s disease is progressive.

Learn how to recognize early symptoms of Parkinson disease »

Frontotemporal dementia is a name used to describe several types of dementia, all with one thing in common: They affect only the front and side parts of the brain, which are the areas that control language and behavior. This type of dementia is sometimes referred to universally as Pick’s disease, though there are multiple forms.

Frontotemporal dementia affects people as young as 45 years old. Although scientists don’t know what causes it, it does run in families and people with it have mutations in certain genes, according to the Alzheimer’s Society.

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

Unlike in Alzheimer’s, memory problems associated with frontotemporal dementia tend to occur later in the progression of the disease.

Frontotemporal dementia is the most common form of dementia that occurs in people with amyotrophic lateral sclerosis, or ALS.

Creutzfeldt-Jakob disease (CJD) is one of the rarest forms of dementia. Only 1 in 1 million people are diagnosed with it every year, according to the Alzheimer’s Association. 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 suffer from depression. Confusion and loss of memory are also common. CJD affects the body as well, causing twitching and muscle stiffness.

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


Prions and the diseases they cause are not well understood by experts, but CJD cases are generally broken down into the following three categories:

  • Sporadic Creutzfeldt-Jakob disease. This is the most common, in which the origin of prion spread remains a mystery.
  • Familial Creutzfeldt-Jakob disease. This is caused by inherited genetic changes that can generate the production of prion protein.
  • Acquired Creutzfeldt-Jakob disease. Though now exceedingly rare, versions of CJD can be caused by exposure to abnormal prion protein, primarily through consumption of infected meat.

Wernicke’s disease, or Wernicke’s encephalopathy, is a type of brain disorder that’s caused by a lack of vitamin B-1, leading to bleeding in the lower sections of the brain. Wernicke’s 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.

Korsakoff syndrome is a memory disorder caused by advanced Wernicke’s disease. People with Korsakoff syndrome may have trouble:

  • processing information
  • learning new skills
  • remembering things

The two conditions are linked and are usually grouped together as one condition, known as Wernicke-Korsakoff syndrome. Though the symptoms resemble those of most other dementias, Wernicke-Korsakoff syndrome is unique in that it is preventable, and, when addressed early, treatable.

Wernicke-Korsakoff syndrome can be a result of malnutrition or chronic infections. However, the most common cause for this vitamin deficiency is alcoholism.

Sometimes people with Wernicke-Korsakoff syndrome make up information to fill in the gaps in their memories without realizing what they’re doing.


Though Wernicke-Korsakoff syndrome can be difficult to diagnose because of the many possible explanations for its symptoms, treatment is possible. In addition to hospitalization, treatment usually involves the following:

  • vitamin B-1 given through an intravenous line (IV) in the arm or hand
  • vitamin B-1 given by mouth
  • a balanced diet to keep vitamin B-1 levels up
  • treatment for alcoholism (if determined to be a cause)

Mixed dementia refers to a situation where 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. According to the Jersey Alzheimer’s Association, up to 45 percent of people with dementia have mixed dementia but don’t know it.

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 will 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. The ventricles are fluid-filled spaces designed to cushion a person’s brain and spinal cord. They rely on just 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. According to Johns Hopkins Medicine, an estimated 5 percent of dementia cases are due to NPH.

Seeking treatment as early as possible can help a doctor intervene before additional brain damage occurs. Normal pressure hydrocephalus is one of the types of dementia that can sometimes be cured with surgery.

Causes and symptoms

Some of the potential causes of NPH include:

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

However, sometimes doctors don’t know the cause of NPH. Symptoms include:

  • poor balance
  • forgetfulness
  • changes in mood
  • depression
  • frequent falls
  • loss of bowel or bladder control

Huntington’s disease is a genetic condition that causes dementia. Two types exist: juvenile and adult onset. The juvenile form is rarer and causes symptoms in childhood or adolescence. The adult form typically first causes symptoms in a person when they’re 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 trouble swallowing. The symptoms of dementia in Huntington’s disease are similar to those of most other forms of dementia, with mood changes, anger, and depression particularly common.

Many diseases can cause dementia in the later stages. For example, people with multiple sclerosis can develop dementia. It’s also possible for those with HIV to develop cognitive impairment and dementia, especially if they’re not taking antiviral medications.