What is Alzheimer’s Disease?
Alzheimer’s disease is the most common cause of dementia in older adults. It is a progressive disorder that causes brain cells to waste away (degenerate) and die.
Nearly 7 million Americans are living with Alzheimer’s disease. Unless an effective treatment or cure is identified, this number is projected to more than double by the year 2060.
What is dementia?
Dementia is not a specific disease. It is a condition where problems with memory, thinking, or behavior interfere with our ability to perform daily activities safely and independently. We all forget sometimes, and it is normal for people to become more forgetful as we get older. Who hasn’t misplaced their keys, forgotten a medication dose, or forgotten to pay a bill at one time or another? But dementia is not a part of normal aging. In dementia, problems in memory and thinking abilities become severe enough to cause problems carrying out responsibilities of daily life and make it difficult to remain independent.
Are AD and dementia the same?
Alzheimer's disease is the most common cause of dementia in older adults, but it is only one type of dementia. Other conditions can also cause memory loss.
The dementia of Alzheimer’s disease is caused by the build-up of proteins in and around brain cells that form clumps and tangles, causing the cells to malfunction and die. The two specific proteins in AD are amyloid (which form clumps or “plaques” outside of brain cells) and tau (which forms tangles of disintegrating cell parts inside brain cells). These changes typically start in the memory center of the brain, which is why memory loss is often an early symptom in Alzheimer’s disease.
Alzheimer’s disease is called a “neurodegenerative” dementia because the build-up of proteins does not stop, brain cells continue to die, and symptoms continue to worsen gradually over time. Although memory loss is usually the first and most prominent symptom, over time Alzheimer's disease can impact communication, problem solving, way-finding, mood, and behavior. In some less common forms of Alzheimer's disease, cell changes start in other areas of the brain, causing problems with other thinking abilities to show up first.
Learn the 10 Early Signs of Alzheimer's, as compiled by the Alzheimer's Association.
What is Mild Cognitive Impairment?
Mild cognitive impairment (MCI) is a condition where a decline in memory, thinking, or behavior has occurred, but it is not severe enough to cause problems managing responsibilities of daily life independently. The decline is not due to a known condition such as a stroke, head injury, or brain tumor.
People with MCI are at increased risk of developing Alzheimer's disease or AD-related disorder, but a diagnosis of MCI does not mean the person will definitely go on to develop dementia. Some people with MCI do not get worse over time, and a few even get better (if their cognitive change is due to other conditions that are identified and treated).
What is Subjective Cognitive Decline?
Subjective cognitive decline is a feeling of worsening memory or thinking abilities that is noticed by an individual but has not been confirmed by formal examination. That is, the person demonstrates “normal” ability for their age on formal cognitive testing. As a result, they do not meet criteria for a diagnosis of mild cognitive impairment or dementia. In some people, subjective cognitive decline may be a very early indicator of a future diagnosis of MCI, although it can often be the result of other conditions such as depression, stress, chronic pain, or sleep difficulties. Experiencing subjective cognitive decline can be anxiety-provoking or otherwise affect their emotional well-being. Brining subjective cognitive decline to the attention of your healthcare team can help you better understand your symptoms, manage anxiety, and monitor your cognitive health.
How does AD affect the brain?
This brief video, from the National Institute on Aging shows how Alzheimer's disease causes changes in the brain that result in difficulties with memory, thinking, and behavior. It also shows how some very important work is being done to find a way to delay or prevent the onset of disease.
What are other types of dementia?
Many conditions can cause someone to experience problems with memory, thinking, or behavior to the degree that they have trouble performing daily activities safely and independently.
Lewy body dementia and frontotemporal dementia are similar to Alzheimer's disease in that they are caused by abnormal proteins that build up in the brain. Early symptoms typically differ from Alzheimer's because the regions of the brain that are first and most affected by the proteins are outside the memory center. In Lewy body dementia, problems start in the parts of the brain controlling attention, movement, and alertness. In frontotemporal dementia, early changes are seen in the parts of the brain that control behavior and/or our ability to communicate.
Vascular dementia is the 2nd most common type of dementia and is caused by strokes or other problems with blood vessels that supply blood, oxygen and nutrients to the brain.
Infections, thyroid disorders, blood sugar problems, nutrition deficiencies, medications, and brain tumors are medical conditions that can cause dementia that may improve with treatment.
As noted earlier, conditions such as sleep disorders, stress, depression, anxiety, and chronic pain can also contribute to memory loss. Memory may return to normal when these conditions are treated and controlled.
LEARN MORE
- Informational videos on Alzheimer's disease and AD-related disorders on the Mayo Clinic ADRC You Tube Channel.
- Information about Mild Cognitive Impairment and Alzheimer’s disease on the Mayo Clinic website.
- Mayo Clinic ADRC online resources for people with Alzheimer’s Disease or AD-related disorders and their families.
- Additional information from the Alzheimer’s Association and National Institute on Aging