Alzheimer’s disease

Learn about Alzheimer’s disease and what we’re
doing to help

What is Alzheimer’s disease?

Alzheimer’s disease (AD) is a disease of the brain that typically progresses slowly. People with AD have memory loss and eventually lose their ability to think clearly and to carry on their daily activities.

AD is the most common form of dementia - a syndrome in which there is deterioration in memory, thinking, behavior and the ability to perform everyday activities. AD accounts for up to 60-70% of dementia cases worldwide. It’s estimated around 50 million people around the world have AD.

Are there different stages of AD?

AD is a continuous process, and each patient will have different experiences and symptoms. The disease progresses through five stages, from preclinical to severe:


At this stage, people with AD won’t have any noticeable symptoms, and this can last for years or even decades. Preclinical AD is usually only identified in research settings where people are screened for protein deposits in the brain, described in Causes, below.

Mild cognitive impairment (MCI)

Mild changes in memory and thinking ability occur, but not enough to affect work, relationships, or the ability to carry out activities of daily living. People with MCI may find it harder to make decisions and notice changes in their ability to remember things like appointments or conversations.

Mild dementia due to AD

Symptoms become more obvious, as daily functioning can be impacted. People with mild dementia due to AD may ask the same question over and over, have difficulty completing more complex tasks and they, or those around them, may notice changes in their personality and may get lost more frequently, even in familiar places.

Moderate dementia due to AD

People with moderate dementia due to AD may have greater memory loss and need help with daily activities and more supervision as they become increasingly confused and forgetful. Changes in personality and behavior tend to be more significant at this stage.

Severe dementia due to AD

Movement may be affected, as well as speech. People with severe dementia due to AD may lose the ability to communicate in a way they can be understood and need help with dressing and using the bathroom. They may start to experience difficulty walking, swallowing and controlling their bladder and bowel movements.

What causes AD?

We don’t know exactly what causes AD, but it’s thought to be to be a combination of genetic, lifestyle and environmental factors. What we do know is that, in AD, brain proteins don’t function as they should. That’s why research currently focuses on the role of two proteins:


Beta-amyloid fragments cluster together into larger deposits called amyloid plaques. The plaques appear to have a toxic effect on neurons (nerve cells), which stops messages passing from one cell to another.


Tau proteins change shape and form tangles inside neurons – commonly known as tau tangles – compromising the normal function and health of neurons.

What are potential risk factors for AD?


As you grow older, the likelihood of developing AD increases.

Genetics and genetic mutations

Researchers have found several genes that increase the risk of AD. And, a small percentage of AD cases (thought to be 1% or less) develop due to mutations of specific genes.

Family history

People who have a parent or sibling with AD are more likely to develop the disease.

Modifiable risk factors

These are things that can be changed or modified to reduce the risk of AD, such as being physically active, moderating alcohol intake, not smoking, staying socially and mentally active, reducing blood pressure, and eating healthily.

Depending on where you live in the world, your ethnicity may affect how likely you are to get AD. In the United States, Hispanic and/or Latin Americans may be 1.5 times more likely to develop Alzheimer’s and other dementias compared to non-Hispanic White people. And Black and/or African Americans are about 2 times more likely to develop Alzheimer’s and other dementias than non-Hispanic White people. But people of Black/African American and Hispanic/Latin heritage are currently underrepresented in AD clinical trials.

That’s one of the reasons why our ongoing research is so important – we need to understand not only how AD affects everybody with the condition, but why some people are disproportionately affected. Understanding this can also help us to learn how to help people with AD in the future.

Our AD research

Biogen’s specific area of AD research looks at whether investigational drugs may potentially slow the progress of the disease, and help with the memory loss and reduced ability to carry out everyday tasks associated with the disease.

AD is hallmarked by two proteins – amyloid plaques and tau tangles.

The research Biogen is conducting aims to reduce existing protein deposits in the brains of people with early AD in order to potentially slow the progression of the disease.

As part of our ongoing commitment to people living with AD we continue to evaluate the safety and effectiveness of the drugs we’re developing.

What could a Biogen AD trial involve?

Before you join a trial, the study team first confirm your eligibility with some health assessments. Then, if you’re eligible and choose to take part in an AD trial, you’ll need to attend several appointments so that the trial team can closely monitor your health and condition with health assessments, such as:


To assess how well you’re thinking, performing daily activities, and how you’re feeling.

PET scans

Positron emission tomography (PET) scans use a special dye called a tracer to take pictures of your brain. PET scans can be used to monitor the changes in levels of amyloid beta and tau proteins in the brain.

MRI scans

Magnetic resonance imaging (MRI) scans use a magnetic field and computer-generated radio waves to create detailed images of the organs and tissues in the body, including 3D images that can be viewed from different angles. MRI scans can monitor for potential fluid shifts in the brain that may be a sign of swelling or microbleeds.

Lumbar puncture

Lumbar punctures involve inserting a needle between the bones of the spine in your lower back, in order to take a small amount of cerebrospinal fluid (fluid surrounding the brain and spinal cord). This will be analyzed for the presence of proteins. The trial doctor will discuss any risks associated with this procedure with you, including, but not limited to: headache and back discomfort/pain.

Other assessments will be involved. A full list of these, and all other requirements around taking part in a trial, would be fully discussed with you before you made a decision about whether to join a trial or not.

Depending on the assessments required at each visit, you may be able to complete some of the visits at home or over the phone. However, for some specific visits you may have to travel to the trial site or clinic.

And remember, if you join a clinical trial, there are many rules and regulations in place to protect your rights, safety, welfare and personal data.

What is the role of a caregiver in an AD clinical trial?

Someone who cares for you, for example, a partner, sibling, other family member, close friend, or professional caregiver, may be there to assist. This may be to help you get to and from your appointments and support you throughout the trial. Or, they might be asked to help monitor any changes in your condition and report them to us. Visit our section on caregivers for more information about their role.

How can I get involved?

To find new treatment options for AD, we must first test investigational drugs in clinical trials. But in the same way that diseases like AD can impact groups of people in different ways, how medicine works in the body can also vary for different groups of people. That’s why it’s so important that a diverse group of people take part in clinical trials.

You can learn more about the importance of diversity in clinical trials, and Biogen’s efforts to make an impact, here.

Recruiting Alzheimer’s disease trials:

Click to view full study details including trial locations.

Biogen is also pursuing the development of potential new treatments through collaborations with other companies. You may not find those trials on Biogen Trial Link. To learn more about these collaborations, please visit our pipeline page on

Help and resources

There are organizations that offer information and support for people living with AD and their families. Below are some groups where you can find out more about AD, connect with others, or learn about the latest research. Remember, this list of organizations does not imply an endorsement from Biogen or the listed organization.