What Is Dementia?

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Dementia is not one disease, but a term that refers to different disorders that affect the brain and impair a person’s memory, thinking, behavior, or emotions enough to interfere with daily life and independence.

Alzheimer’s disease is the most common type, accounting for 60% to 80% of all dementia cases. Other types of dementia include vascular, Lewy body, frontotemporal, and mixed dementia, which refers to dementia from more than one cause. Although dementia is more common with age, it is not considered a normal part of aging.

This article will examine the signs, causes, diagnosis, treatment, and prevention of dementia.

Younger Woman and Older Woman Sitting Together

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About one in nine people, or approximately 6.5 million Americans, ages 65 and older have Alzheimer’s disease, the most common type of dementia.

Signs of Dementia

Because dementia refers to multiple conditions, symptoms can vary greatly between individuals. Symptoms can occur as nerve cells in the brain stop working properly and eventually die. Symptoms may also be due to a buildup of plaque in the brain.

Dementia occurs in stages, with symptoms typically progressing from mild, where the person can still function independently, to severe, where round-the-clock care is often needed.

Cognitive symptoms

Some common cognitive symptoms of dementia include problems with:

  • Short-term memory. The person might forget or be confused about names, words, dates, or memories, or ask the same questions repeatedly. They may get lost or disoriented in familiar areas. Memory loss is one of the most common symptoms of Alzheimer’s disease, especially when it’s in the early stages.
  • Communication. This can include using unusual words when referring to familiar objects, or having trouble speaking, reading, or writing.
  • Reasoning, judgment, and problem-solving. The person might not be able to complete tasks he or she used to do without help. This can include things like managing bills and money, or making lists and following recipes.
  • Attention. Those with dementia might lose interest in activities or events they used to enjoy.

Psychological symptoms

Some of the psychological symptoms of dementia include:

  • Mood and personality changes. People with dementia can become confused, anxious, and suspicious. They may accuse others of stealing from them, be easily upset with others, or act impulsively. A person with dementia may also act aggressively.
  • Withdrawing socially. A loss of the ability to communicate or pay attention can lead to a person withdrawing from activities and hobbies they used to take part in.
  • Hallucinating, or experiencing delusions or paranoia 

In addition to cognitive and psychological symptoms, those with dementia can also experience physical symptoms such as loss of balance and coordination, or changes in visual perception.


Dementia is caused by changes in the brain, but in many cases the exact mechanisms that lead to dementia are unknown. For example, Alzheimer’s is believed to be caused by multiple factors including age-related brain changes, genetics, and environmental and lifestyle factors.

Amyloid plaques are known to play a role in Alzheimer’s disease. Amyloid plaques are made up of collections of beta-amyloid protein that form in the spaces between the brain’s nerve cells. This build-up of protein causes damage and makes it harder for cells to communicate with each other. However, scientists are still unsure exactly how amyloid plaque damages nerve cells.

Another characteristic of Alzheimer’s disease is the presence of neurofibrillary tangles called “tau” tangles in the brain. These tangles, caused by a buildup of tau protein, cause changes in the brain that appear to particularly affect memory.

Frontotemporal dementia and Lewy body dementia are also associated with abnormal amounts of certain proteins in the brain, while vascular dementia is caused by conditions that affect blood flow in or to the brain.

Risk factors

A number of risk factors are associated with an increased chance of developing dementia.

Unmodifiable risk factors, or risk factors you can’t control, include:

  • Age. This is the biggest known risk factor for dementia, with the majority of cases occurring in those ages 65 and older.  
  • Genetics. Having a family history of dementia increases your risk of getting it. There are more than 20 genes known to increase the risk of developing dementia.
  • Race/ethnicity. Older Black Americans are two times more likely to have dementia than white Americans, and Hispanics are 1.5 times more likely to have dementia than white Americans.
  • Sex. Women are more likely than men to experience dementia. In 2020, 35 million women worldwide had Alzheimer’s disease, compared to 20 million men. Women are more than twice as likely as men to die from dementia.

Alzheimer's and Age

It's estimated that 5% of American ages 65 to 74 have Alzheimer’s disease, compared to 13.1% of those ages 75 to 84, and 33.2% of those ages 85 or older.

Modifiable risk factors, or those you can control, also play a role in the chances of developing dementia. They include:

  • Unhealthy lifestyle behaviors. Being obese, physically inactive, smoking, and drinking too much alcohol all increase dementia risk.
  • Heart disease/hypertension. Research is finding that brain health has an important connection to heart health. Having cardiovascular disease or high blood pressure increases the risk of developing dementia.
  • Diabetes. Having diabetes is a known risk factor for developing Alzheimer's disease and vascular dementia.
  • Social isolation. Having social connections has been shown to enhance brain function and reduce dementia risk.


There is no one test to diagnose dementia. Healthcare providers typically will do a physical exam, take a medical assessment including family history, and run lab tests to first determine if another condition is causing symptoms.

Tests that can be used to diagnose dementia include:

  • Cognitive and neurological tests. These tests evaluate both mental and physical function including memory, language, and sensory responses.
  • Brain scans. Imaging including CT scans and magnetic resonance imaging (MRI) might be ordered to look for evidence of stroke or other changes in the brain that could be causing symptoms.
  • Blood testing. A blood test measuring levels of beta-amyloid proteins associated with Alzheimer’s may be ordered.


How dementia is treated depends on the type of dementia and if there is a known cause. In most cases, dementia cannot be cured. Medications can improve symptoms, mental function, and behavior, but do not slow dementia progression.

In 2021, the FDA fast-tracked approval for an intravenous drug called Aduhelm (aducanumab) for the treatment of mild cognitive impairment due to Alzheimer’s disease. Aduhelm is the first drug designed to remove amyloid proteins from the brain. However, the use of this drug has been controversial for several reasons including the potential for serious side effects including brain swelling and bleeding, and because the drug was not shown to significantly improve cognition in clinical trials.


Because the causes of dementia aren’t fully understood, there is no guaranteed way to prevent it. However, managing modifiable risk factors can lower your risk of getting dementia.

Behaviors that can reduce the risk of developing dementia include:

  • Exercising regularly
  • Eating a healthful diet
  • Maintaining a healthy weight
  • Not smoking
  • Managing health conditions linked with dementia such as diabetes and high blood pressure
  • Participating in social activities
  • Engaging in mentally-stimulating activities


Dementia is an umbrella term referring to a number of conditions that affect the brain and impair cognitive, psychological, and physical function. In most cases, the causes of dementia are not known, and a number of factors are believed to play a role.

The chance of being diagnosed with dementia increases greatly with age. Treatments can be used to help manage symptoms but do not slow dementia's progression. Making healthy lifestyle modifications can help lower the risk of getting dementia.

A Word From Verywell

Dementia can be a difficult diagnosis for both patients and their loved ones. If someone is displaying signs of dementia, it’s important to see a healthcare provider as soon as possible to make a diagnosis and rule out any other conditions that could be causing symptoms.

Medications and lifestyle changes can potentially improve symptoms but are most effective if initiated in dementia’s early stages. Because dementia is progressive, it’s also important to explore available resources early on. There are many organizations that offer support to both patients with dementia and their caregivers throughout all stages of the condition.

Frequently Asked Questions

  • What is the difference between dementia and Alzheimer's?

    Dementia is an umbrella term for certain conditions that affect the brain, and how a person thinks, remembers, and behaves. Alzheimer’s disease is one of several types of dementia. It is also the most common type of dementia.

  • What is the main cause of dementia?

    Although dementia is caused by changes in the brain, scientists still aren’t sure what the exact causes of dementia are. It’s likely that dementia has multiple causes including physical changes to the brain, genetics, and lifestyle factors.

  • How long do people with dementia live?

    People can live many years with dementia and remain physically healthy as their cognitive abilities decline. Although on average a person lives four to eight years after being diagnosed with Alzheimer’s disease, it’s possible to live up to 20 years or more with the disease.

17 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  12. Stanford Health Care. Risk factors for dementia.

  13. Stanford Health Care. Treatment options for dementia.

  14. Duke Health. What you need to know about aducanumab.

  15. Stanford Health Care. Can dementia be prevented?.

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  17. Alzheimer’s Association. Stages of Alzheimer’s.

By Cathy Nelson
Cathy Nelson has worked as a writer and editor covering health and wellness for more than two decades. Her work has appeared in print and online in numerous outlets, including the Detroit Free Press and The Detroit News.