What is Alzheimer's disease?

Diana Meeks
Diana Meeks on behalf of Sigma Nursing
Family Practitioner

Alzheimer's disease (AD) is an age-related, non-reversible brain disorder that develops over a period of years. Initially, people experience memory loss and confusion, which may be mistaken for signs usually associated with normal aging. However, the symptoms of AD gradually lead to behavior and personality changes, a decline in cognitive abilities, such as decision-making and language skills, and problems recognizing family and friends. AD ultimately leads to a severe loss of mental function. This loss is related to the breakdown of the connections between certain neurons in the brain and their eventual death. AD belongs to a group of disorders called dementias, which are characterized by cognitive and behavioral problems. It is the most common cause of dementia among people age 65 and older.

Three major hallmarks in the brain are associated with the disease processes of AD:

  • Amyloid plaques: These plaques are made up of fragments of a protein called beta-amyloid peptide mixed with a collection of additional proteins, remnants of neurons and bits and pieces of other nerve cells.
  • Neurofibrillary tangles (NFTs): NFTs found inside neurons, are abnormal collections of a protein called tau. Normal tau is required for healthy neurons. However, in AD, tau clumps together. As a result, neurons fail to function normally and eventually die.
  • Loss of connections between the neurons responsible for memory and learning: Neurons cannot survive when they lose their connections to other neurons. As neurons die throughout the brain, the affected regions begin to atrophy, or shrink. By the final stage of AD, damage is widespread and brain tissue has shrunk significantly.

This answer is based on source information from the National Institute of Diabetes and Digestive and Kidney Diseases.

Dr. Zaldy S. Tan, MD
Geriatric Medicine Specialist

Alzheimer’s disease is one form of dementia. Dementia is a term doctors use to describe a number of conditions that result in a disruption of the brain’s memory and thinking functions. We can compare “dementia” and “Alzheimer’s” to “color” and “blue.” Just like blue is only one type of color, Alzheimer’s is only one type of dementia. Alzheimer’s is the most common form of dementia, accounting for about seven out of 10 cases of dementia. Alzheimer’s usually follows a progression:

  • Initially, it affects only the short-term memory.
  • Over time (months to years), it affects other cognitive functions, such as:
    • Reasoning
    • Judgment
    • Problem solving
    • Planning
    • Impulse control
  • Finally, the disease affects motor functions such as walking and swallowing.
Dr. Michael T. Murray, ND
Naturopathic Medicine Specialist

Alzheimer's disease (AD) is a degenerative brain disorder that manifests as a progressive deterioration of memory and mental function, a state of mind commonly referred to as dementia. In the US, 5 percent of the population over age 65 suffers from severe dementia, while another 10 percent suffers from mild to moderate dementia. With increasing age, there is a rise in frequency. For example, in people over age 80, the frequency rate for dementia is over 25 percent.

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Alzheimer's disease (AD) is the most common form of dementia, a term used to describe a group of symptoms affecting intellectual and social abilities severely enough to interfere with daily functioning.

Alzheimer's disease occurs in one in ten people over the age of 65. According to recent assessments, the rate of Alzheimer's disease is going to nearly double every 20 years. By 2050, 43 percent of those with Alzheimer's disease will need high-level care, equivalent to that of a nursing home.

Alzheimer's disease is often thought about in three stages:

  • Mild Alzheimer's disease (also called early-stage). In mild AD, the first stage, people often have some memory loss and small changes in their personality. They may have trouble remembering recent events or the names of familiar people or things. They may no longer be able to solve simple math problems or balance a checkbook. People with mild AD also slowly lose the ability to plan and organize. For example, they may have trouble making a grocery list and finding items in the store.
  • Moderate Alzheimer's disease. This is the middle stage of AD. Memory loss and confusion become more obvious. People have more trouble organizing, planning and following instructions. They may need help getting dressed and may start having problems with incontinence. This means they can't control their bladder and/or bowels. People with moderate-stage AD may have trouble recognizing family members and friends. They may not know where they are or what day or year it is. They also may lack judgment and begin to wander, so people with moderate AD should not be left alone. They may become restless and begin repeating movements late in the day. Also, they may have trouble sleeping. Personality changes can become more serious. People with moderate AD may make threats, accuse others of stealing, curse, kick, hit, bite, scream or grab things.
  • Severe Alzheimer's disease (also called late-stage). This is the last stage of Alzheimer's and ends in the death of the person. In this stage, people often need help with all their daily needs. They may not be able to walk or sit up without help. They may not be able to talk and often cannot recognize family members. They may have trouble swallowing and refuse to eat.
Dr. Mehmet Oz, MD
Cardiologist (Heart Specialist)

Alzheimer's disease is a progressive brain disease that slowly destroys memory and thinking skills and, over time, the ability to carry out the simplest tasks of daily living. Symptoms of AD usually first appear after age 60. Although there are some medical treatments to slow the progression of this disease, no cure currently exists.

Alzheimer’s is the most common form of dementia, which is a broad term used to describe the loss of memory and other cognitive abilities. A progressive disease, Alzheimer’s is mild at first and becomes more severe over time.

Dr. Rudy Tanzi, PhD

As America's population ages, the rate of Alzheimer's disease is skyrocketing. In this video, Dr. Rudy Tanzi explains what the disease is and why it's so devastating.

Alzheimer's disease is a degenerative brain disorder that results in memory loss, impaired thinking, difficulty finding the right word when speaking and personality changes. Its course is marked by a continual loss of neurons (nerve cells) and their connections with other neurons (synapses) that are crucial to memory and other mental functions. In advanced Alzheimer's disease, the dramatic loss of neurons causes the brain to shrink. Levels of many brain chemicals known as neurotransmitters, which carry complex messages among billions of nerve cells, are also diminished. After the symptoms first appear, people live anywhere from 2 to 20 years in an increasingly dependent state that exacts a staggering emotional, physical and economic toll on families.

There is no cure and little that can be done by way of prevention. But early diagnosis is important because drugs are available that may temporarily improve or stabilize worsening of cognitive symptoms, and they work best in the early stages of the disease.

Judith London, MD
Psychiatrist (Therapist)

As debilitating as Alzheimer's is, people with this disease are able to still have thoughts and ideas although they are not expressed the way the used to be. It's important for us to remember that there still is a person inside, and not assume that because this disease affects the brain that feelings and ideas cease to exist.

Dr. Eric Pfeiffer
Psychiatrist (Therapist)

Alzheimer’s disease is a disease of the brain whose cause is not fully understood. It affects people in their later years, through no fault of their own. It gradually takes over, first a few, then more and more areas of a person’s life. It is in fact a disease like no other. It affects nearly six million people in the United States at this time, and that number is going to double in the next twenty years. The reason for this is that more and more people live into their seventies, eighties and nineties, and the prevalence of the disease increases drastically with each advancing decade. Thus, only 10 percent of people in their seventies have the disease, but it increases to 30 percent of people in their eighties, and to nearly 50 percent of people in their nineties. Some people have called Alzheimer’s a monster disease, not only because it affects a huge number of people, but also because of what it does to those affected. It gradually eats away layer after layer of human functioning, starting with memory and decision making capacity, and continuing to erode deeper and deeper layers of the personality. It attacks language, judgment, ability to communicate and self-care capacity. Even more vexing than these losses is an accumulation of troublesome behaviors that increase gradually as the disease advances. Effective caregiving is what humanizes this ordeal, both for the person with the disease and the caregiver. Caregiving is what makes it possible to live with this disease rather than be overwhelmed by it.

It is important to realize that Alzheimer’s is a disease, not simply a manifestation of old age. It is a disease in which brain cells die prematurely and progressively, leaving the individual with gradually decreasing abilities in their thinking, feeling and behavior.

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According to the American Academy of neurology, Alzheimer's disease is an age-related nonreversible brain disorder. It typically progresses over several years and begins with memory loss and confusion. Alzheimer's disease can gradually lead to behavior and personality changes and can also affect decision making and recognition of family and friends. Usually those affected will have more problems with recent memory loss versus long-term memory, which is not as affected.

Alzheimer's disease is the most common cause of dementia, or loss of intellectual function, among people aged 65 and older. It is not a normal part of aging.

This progressive, degenerative disorder attacks the brain's nerve cells, or neurons, resulting in loss of memory, thinking and language skills, and behavioral changes.

These neurons, which produce the brain chemical, or neurotransmitter, acetylcholine, break connections with other nerve cells and ultimately die. For example, short-term memory fails when Alzheimer's disease first destroys nerve cells in the hippocampus, and language skills and judgment decline when neurons die in the cerebral cortex.

Two types of abnormal lesions clog the brains of individuals with Alzheimer's disease: beta-amyloid plaques, sticky clumps of protein fragments and cellular material that form outside and around neurons, and neurofibrillary tangles, insoluble twisted fibers composed largely of the protein tau that build up inside nerve cells. Although these structures are hallmarks of the disease, scientists are unclear whether they cause it or are a by-product of it.

Alzheimer's disease, the most prevalent form of dementia, is a neurodegenerative disease. It represents up to 70 percent of dementia cases. Alzheimer's has no cure and results in death, typically within 10 years of the diagnosis.

In Alzheimer's disease, plaques made up of a brain protein called beta amyloid (or a-beta) form in the spaces between nerve cells, blocking the normal flow of communication between cells and impairing brain function.

Alzheimer's can be compared to coronary artery disease (atherosclerosis), in which plaques composed of cholesterol form in blood vessels and block blood flow to the heart. In Alzheimer's, plaques made up of a brain protein called beta amyloid (or a-beta) form in the spaces between nerve cells, blocking the normal flow of communication between cells and impairing brain function.

Alzheimer’s disease is the most common form of dementia, and is a slow-progressing disease.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.