What Is Dementia?

A Progressive Decline in Memory and Behavior

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Dementia is a condition in which a person experiences stages of decline in memory and cognitive function. There are several distinct types of dementia, and each type produces a characteristic pattern of behavior. It typically affects older adults over the age of 70, but dementia can start sooner in some cases. Knowing what to expect can help when it comes to coping with dementia. 

Dementia causes memory decline and confusion
 Getty Images/Monica Ninker


One of the key features of dementia is that it involves a loss of abilities. Dementia is a gradually progressive disease, although it often seems sudden to the person who has the illness and to other people in their lives.

Once it begins, dementia doesn’t improve. In fact, it usually worsens, with an intermittent decline that continues for years.

The seven stages of dementia range from stage one, with no noticeable symptoms, to stage seven, with severe impairment of function.

The major effects of dementia are:

  • Memory loss
  • Confusion 
  • Difficulty thinking and reasoning
  • Decreased concentration
  • Emotional instability 
  • Agitation 

Medical causes of these issues, such as drug intoxication, an infection, metabolic abnormalities, cancer, and psychiatric disease, are ruled out before a diagnosis of dementia is made.

Warning Signs

According to the Centers for Disease Control and Prevention, over five million Americans have dementia, and it is the sixth-leading cause of death among US adults.

Warning signs include:

  • Forgetfulness
  • Depression
  • Withdrawal from others 
  • Hostility and aggression 
  • Increased injuries
  • Decreased interest in and ability for self-care 
  • Loss of appetite and weight loss 
  • Excessive sleeping
  • Hearing Loss
  • Getting lost 
  • Taking things that belong to others 
  • Paranoia 
  • Inappropriate behavior 
  • Incontinence 

All of these warning signs can occur with any of the types of dementia. The condition eventually has a major impact on the lives of people who have it and on the lives of their families and friends. Not only do people with dementia become less independent, some of the behavioral effects can push loved ones away.

Coping with dementia involves many difficult decisions regarding getting professional help and possibly moving to a nursing home.


Common types of dementia include the following.

Vascular Dementia

This type of dementia occurs when the effects of multiple small strokes affect behavior and thinking skills. The strokes can occur over a period of years, and symptoms can emerge after each stroke, or they may suddenly become apparent all at once. Generally, small chronic strokes are visible on brain-imaging studies in vascular dementia.

Alzheimer's Disease

Alzheimer’s disease is a common type of dementia. The most prominent symptoms are gradually worsening memory loss and confusion. It is associated with a build-up of microscopic particles in the brain called neurofibrillary tangles and amyloid plaques. Sometimes Alzheimer’s disease is associated with shrinking of the brain.

Lewy Body Dementia

Lewy body dementia/dementia with Lewy bodies is characterized by behavioral changes, movements typical of Parkinson’s disease, hallucinations, trouble sleeping, and problems with low blood pressure. This condition is associated with microscopic deposits in the brain that are described as Lewy bodies.

Wernicke-Korsakoff Syndrome

This disease is caused by a deficiency of thiamine (vitamin B1), usually as a result of chronic heavy alcohol use. It is characterized by memory loss, confusion, severely diminished balance, and nystagmus (jerking eye movements).

Frontotemporal Dementia

Frontotemporal dementia (Pick’s disease) causes a rapid decline in memory and thinking skills, difficulty understanding language, diminished concentration, and a loss of behavioral inhibition. It can start at a younger age than some other types of dementia—when a person is in their 40’s or 50’s.

One feature that is often noted with this type of dementia is a shrinking of the frontal and temporal lobes of the brain, which can be identified on brain-imaging tests.

Progressive Supranuclear Palsy

This condition causes difficulty thinking, bouts of uncontrollable laughing or crying, a lack of facial expression, stiff movements, problems with physical balance, and trouble swallowing. It is associated with a build-up of a type of protein in the brain called tau.

Huntington's Disease

This hereditary disease is characterized by involuntary jerking and muscle spasms, delusions, mood swings, and confusion. It begins at an earlier age than other types of dementia—when a person in their 30’s.

Huntington’s disease is inherited in an autosomal dominant manner, which means that children of a person who has the condition will develop the disease if they inherit the gene that causes it—and an average of 50% of the offspring of a person with the disease will inherit it.

Often, a person who has dementia is diagnosed with one of these conditions, but it’s possible to have a diagnosis of one type of dementia and then also develop another type years later, with compounded effects of mixed dementia.


There are several types of dementia. Each type of dementia has its own diagnostic criteria. They all have certain features in common, and they each have distinctive features as well.

All types of dementia cause a gradual degeneration of brain cells, with atrophy (shrinking) of the brain. Most types of dementia affect more specific areas of the brain, such as Alzheimer’s disease, which affects the hippocampus.

A few types of dementia—vascular dementia, Wernicke-Korsakoff syndrome, and Huntington’s disease—have known causes, but most of the time, there aren’t clear risk factors or identifable causes that explain why dementia develops.

End Stage and Coping

Dementia isn’t reversible or curable, but there is a great deal of ongoing research investigating the causes and cures of each type of dementia. Medication may be prescribed to reduce disease progression.

Different ways to cope include:

  • Keep a consistent schedule 
  • Maintain regular physical activity if possible—like walking outdoors 
  • Follow a healthy diet 
  • Avoid unexpected changes 
  • Keep a peaceful and calm environment 

Sometimes major changes to a person’s home have to be made. For example, it might be necessary to put safety covers on the stove or to lock doors where dangerous items (like a ladder or tools) are stored.

Professional Caregiver Support

Often, care of a person with dementia can be exhausting or impossible for family members who aren’t equipped to manage their loved one's needs. Professional caregivers might visit the home to provide relief.

In many instances, people with dementia have to move to a home where professional supervision and care can be provided around the clock. Eventually, dementia leads to death due to issues like malnutrition, infections, blood clots, and fatal falls.

A Word From Verywell

Dementia is a condition that can affect anyone at any time in life. You or someone else may experience dementia, and it can change your life. It’s important not to try to carry the burden alone. Reaching out to medical professionals, family and friends, and caregivers can help provide support and practical help.

3 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.
  1. National Institute on Aging. What is dementia? Symptoms, types, and diagnosis.

  2. American College of Physicians. Current pharmacologic treatment of dementia: A clinical practice guideline from the American College of Physicians and the American Academy of Family Physicians.

  3. Centers for Disease Control and Prevention. What is dementia?

By Heidi Moawad, MD
Heidi Moawad is a neurologist and expert in the field of brain health and neurological disorders. Dr. Moawad regularly writes and edits health and career content for medical books and publications.