Speaking Alzheimer's: A Glossary of Common Terms

Whether you’ve been diagnosed with Alzheimer’s disease, are caring for someone who has the condition, or have an interest in the disease for some other reason, chances are you’ll sometimes come across terms that are new to you.

The following is a quick alphabetical guide to the terminology you may need to know as you learn more about this condition.

Agitation In people with Alzheimer’s, agitation refers to feelings of anxiety they may have. These feelings may cause them to become restless, which may lead them to move around or pace, or become upset in certain places or when trying to remember specific things, like words, dates, or names.

Apathy Loss of motivation may be the most common change in behavior in people with Alzheimer’s. It may result in lack of interest in performing day-to-day activities or increased reliance on caregivers for assistance.

Alois Alzheimer A researcher who, in 1906, first described an “unusual disease of the cerebral cortex” in a woman in her fifties that caused memory loss, disorientation, hallucinations, and ultimately death. Postmortem examination of the woman’s brain revealed several abnormalities, including “neurofibrillary tangles.” It was Alzheimer’s mentor at the Munich medical school, Emil Kraepelin, who christened the condition with Alois's surname.

Amyloid-beta (sometimes called beta-amyloid) A key protein involved in Alzheimer’s disease. Formed from the breakdown of a larger protein called amyloid precursor protein, abnormal levels of this naturally occurring protein collect and “clump” together between the neurons in the brain to form plaques that disrupt cell function.

Aphasia This is a disorder characterized by a loss of ability to comprehend speech. People with aphasia may even lose the ability to speak — or speak properly — themselves. The condition is often confused with Alzheimer’s, because people with Alzheimer’s disease often have difficulty speaking or understanding certain words, because they may not remember their meaning.

Apolipoprotein E (APOE)/Apolipoprotein E4 (APOE4) gene This is the most common gene associated with late-onset Alzheimer’s. APOE has three common forms: APOE e2, which is the least common and which reduces risk for Alzheimer’s; APOE e3, which is the most common and doesn’t play a role in Alzheimer’s disease risk; and APOE e4, which is more common than APOE e2 and appears to increase a person’s risk for Alzheimer’s. You inherit one APOE gene from your mother and another from your father. If you have one APOE e4 gene, that increases your risk for Alzheimer’s disease. If you have two APOE e4 genes, your risk is even higher. But not everyone who has APOE e4 genes develops Alzheimer’s, which means other genetic and environmental factors are involved.

Biomarker These are measures of what is happening inside your body, as revealed through blood, urine, and imaging tests. Biomarkers can help doctors diagnose health conditions and monitor responses to treatment and progression. For example, high cholesterol in the blood is a biomarker for heart disease. In Alzheimer’s disease, the most commonly used biomarkers measure changes in the brain as seen on MRI and PET scans, as well as levels of certain proteins seen on brain scans and in cerebrospinal fluid and blood.

Cerebrospinal fluid (CSF) This is a clear fluid that protects the brain and spinal cord, supplying nutrients and chemicals that keep cells healthy. Proteins, like amyloid-beta, and other substances made by cells can be detected in CSF, and their levels may change years before symptoms of Alzheimer’s disease appear.

Dementia According to the Alzheimer’s Association, this is a general term for decline in mental ability that interferes with daily life. Alzheimer’s disease is the most common cause of dementia, and is a specific condition, while dementia isn’t. Dementia is a group of symptoms associated with decline in memory, reasoning, or other cognitive skills. Many different types of dementia exist, and many conditions cause it. Alzheimer’s accounts for 60 to 80 percent of all dementia cases.

Disorientation People with dementia often become confused in time and space. This may be due to memory loss, which may make it difficult for them to recognize people, places, and objects once familiar to them. Their “internal clock,” which guides them as to when it’s time to eat or go to sleep, may also be affected.

Dysphasia A term often used interchangeably with aphasia, this condition is the impairment of language skills due to damage to the brain caused by stroke or trauma. People with dysphasia may have difficulty understanding, talking, reading, or writing. Dysphasia can differ from person to person, depending on the part of the brain that’s affected.

Healthy Brain Initiative A joint program from the U.S. Centers for Disease Control and Prevention (CDC) and the Alzheimer’s Association, the HBI seeks to educate the public about brain health and empower people with Alzheimer’s and their caregivers. The program will also support initiatives designed to improve access to healthcare services and strengthen education on brain-health-related issues among clinicians.

Frontotemporal disorders These are forms of dementia caused by frontotemporal lobar degeneration, the most common cause of dementia in people younger than age 60. Roughly 60 percent of people with frontotemporal lobar degeneration are 45 to 64 years old. These disorders occur as the result of damage to neurons in the frontal and temporal lobes of the brain. As neurons die in these regions, they atrophy, or shrink, gradually causing difficulties in thinking and behaviors normally controlled by these parts of the brain.

Lewy body dementia Lewy body dementia is a condition associated with abnormal deposits, called Lewy bodies, of a protein called alpha-synuclein in the brain. Lewy bodies change certain chemicals in the brain, causing problems with thinking, movement, behavior, and mood. Also called Parkinson’s dementia, Lewy body dementia can be confused with Alzheimer’s, complicating diagnosis of both conditions.

Microglia Immune cells in the brain that are activated as neurofibrillary tangles of tau protein accumulate. Microglia play a key role in brain development during life and aging. Research suggests they are involved in the early stages of Alzheimer’s and may serve as potential targets for drugs designed to treat the condition.

Mild cognitive impairment A mild cognitive impairment is a slight but noticeable and measurable cognitive decline that may affect memory or decision-making. A person with mild cognitive impairment is at increased risk for developing Alzheimer’s or another dementia.

Mitochondria Thousands of these tiny “organelles” can be found in neurons, and they are essential to brain function. By constantly fusing and dividing, they provide vital energy to neurons, or nerve cells, in the brain. Disruption of this through the accumulation of amyloid-beta causes neurons to stop regenerating. As a result, they gradually die off, causing memory loss, cognitive decline, and other symptoms associated with Alzheimer’s disease.

Mixed dementia A condition in which more than one type of dementia occurs simultaneously in the brain. In the most common form of mixed dementia, the plaques and tangles associated with nerve cells in Alzheimer’s are present along with blood vessel changes associated with vascular dementia — or dementia caused by a stroke or other brain injury.

MRI In Alzheimer’s, magnetic resonance imaging uses magnetic fields and radio waves to create detailed images of the size, shape, and structure of the brain to identify some causes of dementia symptoms or show whether areas of the brain have atrophied, or shrunk. Your doctor may use MRI to identify or rule out other causes of memory loss, like a stroke or brain tumor.

Neurodegeneration The progressive loss of structure or function — or even death — of neurons. Many neurodegenerative conditions — including Parkinson’s and Alzheimer’s — are caused by neurodegenerative processes. In Alzheimer’s, neurodegeneration may be caused by amyloid-beta and tau accumulation, oxidative stress, or mitochondrial dysfunction — or, more likely, all of the above.

Neurofibrillary tangles These are abnormal accumulations of tau protein that collect inside neurons in the brains of people with Alzheimer’s. In healthy neurons, tau binds to and stabilizes structures called microtubules, but in Alzheimer’s disease, chemical changes cause tau to form tangles inside neurons that block their transport system, harming the synaptic communication between them.

Neuroinflammation Chronic inflammation in the brains of people with Alzheimer’s disease that may be caused by the buildup of microglia cells, which are designed to keep the brain free of debris. In Alzheimer’s, microglia fail to clear away beta-amyloid plaques.

Neurons Also called nerve cells, these are the most important cells in the brain and nervous system, because they are responsible for receiving sensory input from the outside world — like what you see and hear — and for sending motor commands to muscles. Researchers believe that disruption in the activity of neurons is key to the progressive decline in cognitive function in people with Alzheimer’s.

Oxidative stress This occurs when excess oxygen free radicals are produced in cells and overwhelm their normal antioxidants, causing damage to cells. Research suggests that the brains of people with Alzheimer’s often have significant oxidative damage caused by amyloid-beta accumulation and the development of neurofibrillary tangles.

Pacing People with Alzheimer’s may become agitated, restless, or worried — and this may cause pacing, or a need to move around. People with Alzheimer’s might wander back and forth, often to the point of exhaustion.

PET scan Positron emission tomography (PET) uses small amounts of a radioactive substance, called a tracer, to measure specific activity in the brain. Fluorodeoxyglucose (FDG) PET scans measure glucose levels in the brain, which may be reduced in people with Alzheimer’s disease, while amyloid PET scans identify abnormal deposits of amyloid-beta. Finally, tau PET scans detect abnormal accumulation of tau, which forms tangles in nerve cells in Alzheimer’s disease.

Plaques Plaques are “clumps” of beta-amyloid proteins in the brain, which form when the brain produces too much of the protein. In Alzheimer’s disease, these plaques collect between neurons and disrupt cell function.

Sundowning This refers to a state of confusion that often occurs in the late afternoon or early evening in people with Alzheimer’s, causing confusion, anxiety, aggression, or inability to follow directions. It can also lead to pacing or wandering. The exact cause is unknown, but it may have to do with being tired at the end of the day.

Tau A protein that works in the neurons of the brain to stabilize structures called microtubules, which help guide nutrients and molecules from the cell body to the axon and dendrites, essentially supplying the brain with the fuel it needs to run properly. In Alzheimer’s, it appears that tau detaches from the microtubules and instead sticks to other tau molecules, eventually forming tangles in the neuron.

Vascular dementia A general term that describes problems with reasoning, planning, judgment, memory, and other processes caused by damage resulting from impaired blood flow to your brain. You can develop vascular dementia after a stroke or as a result of damage caused by another condition, including diabetes or high blood pressure.

Wandering According to the Alzheimer’s Association, 60 percent of people with dementia will wander. People with dementia may not remember their name or address, and can become disoriented, even in familiar places. Anyone who has memory problems and is able to walk is at risk — even in the early stages of dementia. If people with Alzheimer’s become confused about where they are or where they need to go, they may walk in the wrong direction and get lost. This can be a dangerous symptom of the condition, the association says, but there are strategies and services to help prevent it.

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