Understanding Alzheimer’s Disease

Alzheimer’s disease is a type of dementia. Dementia, a group of brain disorders, causes memory loss and other mental difficulties. It usually occurs in older people.  

Important things to know: 

  • Alzheimer’s disease does not have a cure yet, but treatment can slow symptoms and improve quality of life. 
  • Many people become forgetful with age. Forgetfulness does not necessarily mean you have Alzheimer’s. 
  • Research shows that healthy habits, such as exercising and spending time with loved ones, can lower your risk of developing Alzheimer’s. 
  • Scientists, including at the Layton Aging and Alzheimer's Disease Center, are striving to develop better treatments.

What is Alzheimer’s disease?

Alzheimer’s disease is the most common form of dementia. Of those with dementia, about 60-80% are diagnosed with Alzheimer’s disease, according to the Alzheimer’s Association. 

With Alzheimer’s, brain cells gradually die. Their connections vanish, preventing sections of the brain from communicating back and forth. This breakdown causes: 

  • Changes in emotion and behavior that can include depression, anger and restlessness.  
  • Loss of memory, reasoning and thinking.

Living with Alzheimer’s disease

Alzheimer’s is progressive, which means it gets worse over time. Treatment cannot stop the disease, but it can slow the progress of symptoms.  

Changes over time: Early stages cause mild loss of memory and other functions. Gradually, people lose the ability to live independently. By the end of their lives, people with Alzheimer’s need help with all daily activities. 

Rate of progression: How slowly or quickly Alzheimer’s progresses varies with each person. It also varies by type of Alzheimer’s (early or late onset). Some people live with Alzheimer’s up to 20 years after diagnosis. Most live with it for four to eight years. 

Who gets Alzheimer’s disease?

About 5.8 million people in the U.S. are living with Alzheimer’s disease, according to the Alzheimer’s Association. One in 10 people age 65 and older have it, as do nearly one in three age 85 and older.

Alzheimer’s disease risk factors

Certain factors increase the risk of Alzheimer’s disease. Having a risk factor doesn’t mean you will get Alzheimer’s, though, and not having one doesn’t mean you won’t. 

You can’t control some risk factors. They include:  

  • Age: Alzheimer’s is not a normal part of aging, but it is most common among people age 65 and older. 
  • Family history: People who have a parent or sibling with Alzheimer’s are at higher risk. Risk goes up from there if you have more than one relative with Alzheimer’s. 
  • Gender: Women are more likely to develop Alzheimer’s than men. 
  • Race and ethnicity: Black people have about twice the risk compared with white people. Latinos have about 1½ times the risk that white people do.  
  • Genetics: Scientists have identified certain genetic changes that increase risk. They do not fully understand how these changes can lead to Alzheimer’s, though. 
  • Down syndrome: People with Down syndrome are more likely to develop Alzheimer’s. They also tend to develop it about 10 to 20 years earlier than others with the disease. The extra chromosome that causes Down syndrome contains a gene responsible for this higher risk. 
  • Head trauma, or mild memory and thinking issues: People who have had a traumatic brain injury or who have memory or other thinking problems are at higher risk.

Lowering risk of Alzheimer’s disease

You can change your lifestyle to lower your risk. Alzheimer’s disease is linked to heart and blood vessel health, for example. Scientists think damage to blood vessels that supply the brain may play a role. 

To lower your risk, you can: 

  • Quit smoking. 
  • Get regular exercise. 
  • Get enough sleep. 
  • Eat a healthy diet with plenty of fruits and vegetables. 
  • Get treatment to manage health conditions. Be especially alert to depression, type 2 diabetes, high blood pressure and high cholesterol. 
  • Maintain a healthy weight. 
  • Keep your mind active through lifelong learning. 
  • Spend time with family and friends.
Graphic of Alzheimer's Disease Signs and Symptoms, including memory loss, difficulty in problem solving, and more

Stages and symptoms of Alzheimer’s disease

Early stage

In early-stage Alzheimer’s disease, people begin to notice problems such as forgetfulness or confusion. Signs may look like normal aging or those of other conditions. You can usually drive, work, socialize and carry out most daily activities.

  • Trouble with things that were once easy but that take concentration, such as balancing a checkbook, playing a game, or cooking a meal. 
  • Trouble remembering where you left items, including putting things in unusual places. 
  • Confusion in familiar places, such as getting lost on the way to work or home. 
  • Language problems, such as trouble naming people, places or things. 
  • Loss of interest in activities you used to enjoy. 
  • Loss of social skills.  
  • Personality changes such as inability to control emotions.

Moderate stage

Signs and symptoms may interfere with self-care and other daily activities. People may start to need more supervision and care. The moderate stage can last for many years.

  • Difficulty with daily tasks such as dressing, driving, reading or writing. 
  • Inability to remember current events or personal life events. 
  • Poor judgment and inability to perceive danger. 
  • Confused speech, such as using the wrong word or mispronouncing words.  
  • Delusions (fixed beliefs in something untrue) and hallucinations (perceiving things that don’t exist). 
  • Mood changes such as depression, agitation or aggressiveness. 
  • Withdrawal from social contact.

Late stage

People with severe Alzheimer’s need constant help with daily activities. They can no longer converse or respond to what’s happening around them. They may have trouble controlling movements such as swallowing.

  • Inability to recognize family members. 
  • Inability to do daily activities such as eating, dressing and bathing. 
  • Loss of ability to communicate. 
  • Loss of bladder or bowel control. 
  • Difficulty swallowing.  

Swallowing problems can result in food or liquid accidentally entering the lungs, causing aspiration pneumonia. For most people with Alzheimer’s, this pneumonia is the direct cause of death.

When to get checked for Alzheimer’s disease

Everyone forgets things from time to time, especially as we age. But age-related memory problems are quite different from the memory loss that comes with Alzheimer’s. 

People with Alzheimer’s disease may not realize they have a problem, even as family or friends notice changes. If you recognize signs in yourself or a loved one, see a doctor for a full exam.  

Your doctor can use a variety of tests to determine the cause of your symptoms and to rule out other possible causes. Learn about diagnosis and treatment at the Layton Aging and Alzheimer’s Disease Center.

How Alzheimer’s affects brain cells

Medical Illustration of brain and neurons: Healthy vs. Alzheimer's disease

What causes Alzheimer’s disease?

Doctors don’t understand the exact causes. Alzheimer’s may result from a combination of genetic, environmental and lifestyle factors. Some cases result from specific gene changes that can be passed down in families. 

Alzheimer’s disease affects neurons — a type of brain cell. Neurons transmit messages between different parts of the brain, and between the brain and the rest of the body. Changes to neurons and the brain from Alzheimer’s include: 

  • Shrinkage: Also known as brain atrophy, brain shrinkage occurs as neuron networks break down and neurons are destroyed. 
  • Amyloid plaques: Amyloid-beta, a naturally occurring protein, can build up in the brain for reasons that are not fully understood. The buildup forms clumps, known as plaques, between neurons. These plaques keep neurons from communicating.  
  • Neurofibrillary tangles: Tau, another naturally occurring protein, builds up inside neurons. They form threads known as tangles. These tangles block the ability of  neurons to communicate and to transport nutrients. Without nutrients, neurons die.

Types of Alzheimer’s disease

Early onset: Symptoms start in the person’s 40s or 50s. The disease also tends to worsen quickly. This type is much less common than late-onset Alzheimer’s, making up less than 5% of cases. Researchers have identified some genetic factors. 

Late onset: This is the most common type, typically affecting people age 65 and older. Symptoms usually worsen more slowly than in early-onset Alzheimer’s. Late-onset Alzheimer’s disease may run in families, but scientists have not found specific genes.  

Familial Alzheimer’s disease: This rare type results from genetic changes passed down from parent to child. Familial Alzheimer’s makes up less than 1% of cases overall but about 60% of early-onset cases.

Frontotemporal dementia: FTD results from continuing neuron loss in the brain’s frontal lobes (behind the forehead) or temporal lobes (behind the ears). FTD usually begins in a person’s 40s or 50s. It generally causes more problems with behavior and speech than Alzheimer’s does. 

Lewy body dementia: Lewy body dementia (LBD) results from unusual buildup in the brain of a protein called alpha-synuclein. It usually begins in people age 50 and older.  

Parkinson’s disease dementia: Parkinson’s disease first affects areas of the brain that control movement. Changes can spread to areas involved with memory and other thinking.  

Vascular dementia: Reduced blood flow to the brain can cause memory loss and other thinking problems. This is known as vascular dementia, and it’s the most common dementia after Alzheimer’s.  

Mixed dementia: Some people have a combination of dementias, for example Alzheimer’s and vascular dementia. Because doctors cannot diagnose most types of dementia for certain until after a person dies, most people are treated for only one type.

These are some of the brain disorders that can lead to dementia or cause dementia-like symptoms: 

Creutzfeldt-Jakob disease: This rare brain disorder occurs when a protein known as a prion develops an unusual shape. CJD, a fatal illness, causes dementia that worsens quickly. Learn more about prion diseases

Huntington’s disease: A damaged gene produces this inherited, progressive brain disorder. It causes neuron loss, particularly in parts of the brain that control voluntary movement. Symptoms usually begin between ages 30 and 50. Learn more about Huntington’s disease

Korsakoff syndrome: This chronic memory disorder results from a severe lack of vitamin B1 (thiamine), usually due to heavy alcohol use.  

Normal pressure hydrocephalus: NPH occurs when excess fluid builds up in the brain’s ventricles, or cavities. Causes include bleeding, inflammation or infection in the brain. 

Posterior cortical atrophy: This condition occurs in the outer layer of the brain at the back of the head. It may be related to Alzheimer’s disease. It typically begins between ages 50 and 65. It affects the ability to process visual information — impairing reading, for example, and the ability to move through space. 

Genetic testing and Alzheimer’s disease

Testing can show whether you have a version (variant) of a gene that increases your risk of Alzheimer’s. Testing can also uncover the rare cases when an inherited genetic change, or mutation, causes Alzheimer’s. 

At OHSU, we generally do not recommend routine genetic testing for Alzheimer’s because: 

  • Many factors can lead to the disease. 
  • Most people who develop Alzheimer’s do not have a related genetic variant.  
  • Most people who have a variant do not develop the disease.  

Talk with your primary care doctor or to a medical geneticist to learn more or to better understand your risk if you’ve taken a test on your own.

Genetic testing can show whether you carry an inherited gene mutation that causes early-onset Alzheimer’s. In some cases, we may recommend testing to confirm a diagnosis in someone who has signs or symptoms of early-onset Alzheimer’s.  

Some family members, after careful discussion with a genetic counselor, may also want testing to find out whether they carry the mutation.

At-home tests from DNA analysis companies can give consumers access to limited genetic testing, without guidance from a genetic counselor. An at-home test can detect variants that increase the risk of late-onset Alzheimer’s disease.  

It’s important to know, though, that these tests do not diagnose any health conditions. They also don’t check for all variations linked to late-onset Alzheimer's disease. And they don’t check for any mutations linked to early-onset Alzheimer's disease. 

Learn more about the genetics of Alzheimer’s disease from the National Institute on Aging. 

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