What is Alzheimer’s disease?
Alzheimer’s disease (pronounced “alz-HAI-mirs”) is a brain condition that causes a progressive decline in memory, thinking, learning and organizing skills. It eventually affects a person’s ability to carry out basic daily activities. Alzheimer’s disease (AD) is the most common cause of dementia.
The symptoms of Alzheimer’s worsen over time. Researchers believe the disease process may start 10 years or more before the first symptoms appear. AD most commonly affects people over the age of 65.
What is the difference between Alzheimer’s and dementia?
Dementia describes the state of a person’s mental function. It’s not a specific disease. It’s a decline in mental function from a previously higher level that’s severe enough to interfere with daily living.
A person with dementia has two or more of these specific difficulties, including a change or decline in:
- Reasoning and handling of complex tasks.
- Understanding visual form and space relationship.
- Behavior and personality.
Dementia ranges in severity. In the mildest stage, you may notice a slight decline in your mental functioning and require some assistance on daily tasks. At the most severe stage, a person depends completely on others for help with simple daily tasks.
Dementia develops when infections or diseases impact the parts of your brain involved with learning, memory, decision-making or language. Alzheimer’s disease is the most common cause of dementia, accounting for at least two-thirds of dementia cases in people 65 and older.
Other common causes of dementia include:
Who does Alzheimer’s disease affect?
Alzheimer’s disease mainly affects people over age 65. The higher your age over 65, the more likely you’ll develop Alzheimer’s.
Some people develop Alzheimer’s disease before age 65 — typically in their 40s or 50s. This is called early-onset Alzheimer’s disease. It’s rare. Less than 10% of AD cases are early-onset.
How common is Alzheimer’s disease?
Alzheimer’s disease is common. It affects approximately 24 million people across the world. One in 10 people older than 65 and nearly a third of people older than 85 have the condition.
What are the stages of Alzheimer’s disease?
Alzheimer’s disease organizations and healthcare providers use various terms to describe the stages of Alzheimer’s disease based on symptoms.
While the terms vary, the stages all follow the same pattern — AD symptoms progressively worsen over time.
No two people experience AD in the same way, though. Each person with Alzheimer’s disease will progress through the stages at different speeds. Not all changes will occur in each person. It can sometimes be difficult for providers to place a person with AD in a specific stage as stages may overlap.
Some organizations and providers frame the stages of Alzheimer’s disease in terms of dementia:
- Preclinical Alzheimer’s disease.
- Mild cognitive impairment (MCI) due to Alzheimer’s disease.
- Mild dementia due to Alzheimer’s disease.
- Moderate dementia due to Alzheimer’s disease
- Severe dementia due to Alzheimer’s disease.
Other organizations and providers more broadly explain the stages as:
Don’t be afraid to ask your healthcare provider or your loved one’s provider what they mean when they use certain words to describe the stages of Alzheimer’s.
What is preclinical Alzheimer’s disease?
Providers typically only reference the preclinical stage in research on Alzheimer’s disease. People with AD in the preclinical stage typically have no symptoms (are asymptomatic).
However, changes are taking place in their brain. This stage can last for years or even decades. People in this stage aren’t usually diagnosed with Alzheimer’s yet because they’re functioning at a high level.
There are now brain imaging tests that can detect deposits of a protein in your brain called amyloid that interfere with your brain’s communication system before symptoms start.
What is mild cognitive impairment due to Alzheimer’s disease?
When memory problems become noticeable, healthcare providers often identify it as mild cognitive impairment (MCI). It’s a slight decline in mental abilities compared with others of the same age.
You may notice a minor decline in abilities if you’re in the early stages of Alzheimer’s. Others close to you may notice these changes and point them out. But the changes aren’t severe enough to interfere with daily life and activities.
In some cases, the effects of a treatable illness or disease cause mild cognitive impairment. However, for most people with MCI, it’s a point along the pathway to dementia.
Researchers consider MCI to be the stage between the mental changes seen in normal aging and early-stage dementia. Various diseases can cause MCI, including Alzheimer’s or Parkinson’s disease. Similarly, dementia can have a variety of causes.