What Are the Common Types of Dementia?

5 types of dementia

There are currently no cures for these types of dementia, but treatments can improve some symptoms and newer therapies are being tested to slow down disease progression.

1. Alzheimer’s disease. About 6.7 million Americans age 65 and older are living with Alzheimer’s today, making it the most common form of dementia. For most people, symptoms first appear in the mid-60s or later. About one-third of all people 85 and older may have Alzheimer's disease, according to the National Institute on Aging.

The causes of this type of dementia are not fully understood, but it most likely involves abnormal buildup of misfolded proteins known as amyloid plaques that form in the spaces between nerve cells, and tangles of a different protein called tau. The tangles build up inside nerve cells, breaking down cell-to-cell communications as the disease progresses.

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Alzheimer’s affects a person’s memory and eventually the ability to think, reason and perform even the simplest of tasks. Two regions of the brain, which are responsible for memory – the entorhinal cortex and hippocampus – are particularly vulnerable early in the disease. Later, areas in the cerebral cortex become impaired. Those areas are involved in language, reasoning and social behavior.

2. Lewy body dementia. Two types of dementia make up this category: dementia with Lewy bodies (DLB) and Parkinson’s disease dementia (PDD). Both involve abnormal deposits of a protein called alpha-synuclein in the brain. These so-called Lewy bodies produce changes in brain chemicals that can alter movement, thinking, behavior and mood. In both DLB and PDD, people develop movement problems and changes in memory, executive functioning (e.g., planning, organizing) and the ability to identify visual and spatial relationships among objects. Some patients can also experience vivid hallucinations, seeing things that aren’t there, which can be distressing and hard for people to talk about, for fear of severe mental illness. 

For people with DLB, the cognitive changes and motor changes happen around the same time, but people with Parkinson’s disease may have movement problems for years before cognitive changes occur, if they develop at all. It’s difficult to predict.

One risk factor for both Lewy body dementia and Parkinson's disease is REM sleep behavior disorder, in which a person physically acts out their dreams while sleeping.

One of Budson’s patients, a war veteran with Lewy body dementia, had a dream he was back in a war zone engaged in battle. “His wife complained one time she was being strangled by him,” Budson recalls. “Normally when we sleep and have a dream, we are paralyzed, and that’s why we don’t act it out. But patients with Lewy body are not paralyzed. They might run in their sleep. Swim in their sleep. Fight in their sleep.”

3. Vascular dementia. About 10 percent of all dementia cases are vascular, caused by strokes or other problems with blood flow to the brain. The lack of blood flow robs the brain of oxygen and nutrients. Symptoms depend on where in the brain the blood flow is blocked. If a person has multiple strokes or ministrokes, symptoms can worsen. “People lose functions because they develop one stroke after another,” Budson says. “It can be ministrokes, big ones or both. The first time I saw my patient he’d had a stroke that left him unable to write. The next time I saw him, he was unable to calculate the tip in a restaurant. And then he had difficulty dressing himself.”

4. Frontotemporal dementia. Unlike Alzheimer’s, frontotemporal dementia most often strikes younger adults, between the ages of 45 and 64. It results from nerve cell damage in the frontal and temporal lobes of the brain, as the name suggests. There are two primary kinds of frontotemporal dementia. In one form, symptoms show up as unusual behaviors, emotional issues — such as acting or saying things impulsively without regard to other people’s feelings — and difficulty communicating. ​

In the other, the temporal lobes on the side of the brain — the area responsible for speech and language — are affected, creating difficulties understanding and speaking. People forget the meaning of words. “One of my patients with language problems actually forgot what the words for different body parts were,” Budson says. “He didn’t know what a knee or elbow or foot were.” This patient had what is known as the semantic version of primary progressive aphasia.

People with this rare form of dementia may behave impulsively or make reckless financial decisions. “I had a patient some years ago who bought lottery tickets every evening after work,” says Paul E. Schulz, M.D., director of the Neurocognitive Disorders Center at the UT Health Houston McGovern Medical School. “He didn’t pay the mortgage on the office building for a year. His whole garage was stuffed with tickets, barrels full of tickets, millions of tickets.”

Others will eat almost anything, says Budson, recalling a patient who “ate an entire jar of mayonnaise and then a raw steak.”

5. Mixed dementia. Sometimes symptoms come from more than one type of dementia. When a person with Alzheimer’s, for example, suffers a stroke, vascular dementia can result. When more than one type of dementia exists, the disease may progress faster. People older than 80 are especially vulnerable to mixed dementia.